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Sample records for baddeleyite

  1. Boronized steels with corundum-baddeleyite coatings

    Czech Academy of Sciences Publication Activity Database

    Pokorný, P.; Kolísko, J.; Bouška, P.; Brožek, Vlastimil; Kubatík, Tomáš František; Mastný, L.

    2016-01-01

    Roč. 55, č. 3 (2016), s. 341-344 ISSN 0543-5846 Institutional support: RVO:61389021 Keywords : Bobororonized steel * corundum-baddeleyite coating * anti-corrosion properties * plasma spraying Subject RIV: JG - Metallurgy Impact factor: 0.959, year: 2014

  2. Boronized steels with corundum-baddeleyite coatings

    Czech Academy of Sciences Publication Activity Database

    Pokorný, P.; Kolísko, J.; Bouška, P.; Brožek, Vlastimil; Kubatík, Tomáš František; Mastný, L.

    2016-01-01

    Roč. 55, č. 3 (2016), s. 341-344 ISSN 0543-5846 Institutional support: RVO:61389021 Keywords : Bobororonized steel * corundum-baddeleyite coating * anti- corrosion properties * plasma spraying Subject RIV: JG - Metallurgy Impact factor: 0.959, year: 2014

  3. Processes for preparing novel baddeleyite refractory articles

    Energy Technology Data Exchange (ETDEWEB)

    McGarry, Ch.N.; Stunis, J.; Wehrenberg, Th.M.

    1984-07-24

    A novel process for fabricating novel high zirconia content refractory articles directly from novel sinterable compositions including as the major ingredient thereof baddeleyite ore concentrates thereby reducing costs. Appropriate additives, particularly zircon, further provide enhanced resistance to thermal shock damage. Plasticizers, binders and other processing aids are identified for press forming exemplary compositions into continuous casting nozzles, shrouds and other ceramic products typically used in the processing of molten steel, specialty metals and glass.

  4. The oxygen isotope composition of baddeleyite and a test of crystal orientation effects during SIMS analysis

    Science.gov (United States)

    Ibanez-Mejia, M.; DesOrmeau, J. W.; Eddy, M. P.; Kitajima, K.; Valley, J. W.

    2017-12-01

    Baddeleyite, the monoclinic polymorph of ZrO2, is a relatively common accessory phase in undersaturated and alkaline igneous rocks that is rapidly developing into a widely-used tool for studying the age and initial 176Hf/177Hf composition of many terrestrial and planetary rocks that typically lack zircon. The prospect of combining U-Pb-Hf data from baddeleyite with δ18O information, as regularly done with zircon, could prove a very powerful addition to the `analytical toolbox' of the igneous petrologist and for studies of crust and mantle evolution. However, the oxygen isotope systematics of this mineral remain poorly explored, as are the potential analytical hurdles involved in obtaining accurate spatially-resolved δ18O data by SIMS. Here, we report laser fluorination δ18O measurements from two baddeleyite megacrysts from Kovdor (δ18O = 0.24 ± 0.11 ‰) and Phalaborwa (4.58 ± 0.11 ‰), which were subsequently analyzed by SIMS to explore their compositional homogeneity and potential as reference materials for correcting instrumental mass fractionation (IMF). Randomly oriented grain fragments analyzed by SIMS were subsequently mapped using high-resolution EBSD, such that the incidence angle of the Cs+ primary ion beam relative to the baddeleyite crystallographic axes could be determined for each spot. We found that: a) δ18O values for both crystals reproduce fairly well, but several apparent outliers (ca. 10% of all data) were measured with no evident correlation to orientation, cracks or inclusions, suggesting these might not be ideal standards; b) there is a systematic difference in mean measured IMFs of ca. 0.6 ‰ between the two baddeleyite crystals; c) mean 16OH/16O values for Phalaborwa (2.5x10-4) are significantly higher than those of Kovdor (2.9x10-6), suggesting that different degrees of radiation damage affect IMF; and d) there is no statistically significant correlation in our dataset (n= 96 spot analyses) between IMF and crystallographic

  5. Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon.

    Science.gov (United States)

    Moser, D E; Chamberlain, K R; Tait, K T; Schmitt, A K; Darling, J R; Barker, I R; Hyde, B C

    2013-07-25

    Invaluable records of planetary dynamics and evolution can be recovered from the geochemical systematics of single meteorites. However, the interpreted ages of the ejected igneous crust of Mars differ by up to four billion years, a conundrum due in part to the difficulty of using geochemistry alone to distinguish between the ages of formation and the ages of the impact events that launched debris towards Earth. Here we solve the conundrum by combining in situ electron-beam nanostructural analyses and U-Pb (uranium-lead) isotopic measurements of the resistant micromineral baddeleyite (ZrO2) and host igneous minerals in the highly shock-metamorphosed shergottite Northwest Africa 5298 (ref. 8), which is a basaltic Martian meteorite. We establish that the micro-baddeleyite grains pre-date the launch event because they are shocked, cogenetic with host igneous minerals, and preserve primary igneous growth zoning. The grains least affected by shock disturbance, and which are rich in radiogenic Pb, date the basalt crystallization near the Martian surface to 187 ± 33 million years before present. Primitive, non-radiogenic Pb isotope compositions of the host minerals, common to most shergottites, do not help us to date the meteorite, instead indicating a magma source region that was fractionated more than four billion years ago to form a persistent reservoir so far unique to Mars. Local impact melting during ejection from Mars less than 22 ± 2 million years ago caused the growth of unshocked, launch-generated zircon and the partial disturbance of baddeleyite dates. We can thus confirm the presence of ancient, non-convecting mantle beneath young volcanic Mars, place an upper bound on the interplanetary travel time of the ejected Martian crust, and validate a new approach to the geochronology of the inner Solar System.

  6. Purification of baddeleyite concentrate by melting with sulfuric acid and its salts

    International Nuclear Information System (INIS)

    Lebedev, V.N.

    2009-01-01

    Black baddeleyite concentrate of the composition %: 87.4 ZrO 2 , 1.5 SiO 2 , 2.5 TiO 2 , 0.51 Fe 2 O 3 , 1.6 CaO, 3.4 Nb 2 O 5 , 0.59 Ta 2 O 5 has been used for the experiments. Sulfatization was conducted by 93% sulfuric acid with the ammonium, sodium and potassium salts additions. Sulfate mass was leaching at 60 Deg C by water during 1 h. Specific radioactivity of precipitates has been analyzed by radiometric and gamma spectrometric methods. Additions of ammonium, potassium and sodium sulfates increase the degree of decontamination, reduce the consumption of sulfuric acid to 20 %, and the temperature of sulfatization. Degree of decontamination increases with increasing additives in the system Na 2 SO 4 >(NH 4 )SO 4 >K 2 SO 4

  7. Zircon and baddeleyite from the economic ultramafic-mafic Noril'sk-1 intrusion (Russia): Hf-isotope constraints on source composition

    Science.gov (United States)

    Malitch, K. N.; Belousova, E. A.; Badanina, I. Yu.; Griffin, W. L.

    2012-04-01

    The ultramafic-mafic Noril'sk-1 intrusion in the northwestern part of the Siberian Craton (Russia) represents one of three known Noril'sk-type, ore-bearing intrusions, which host one of the world's major economic sulphide platinum-group-element (PGE)-Cu-Ni deposits. Zircon and baddeleyite dated previously both by SHRIMP (i.e. 248.0 ± 3.7 Ma, Campbell et al. 1992) and ID-TIMS (251.1 ± 3.6 Ma, Kamo et al. 1996) have been restricted to one lithology (e.g. leucogabbro) of the Noril'sk-1 intrusion. To better constrain the age of igneous event and sources involved in its generation our multi-technique study utilized ten rock samples characteristic of unmineralized and mineralized lithologies. The rocks investigated comprise (from top to bottom) gabbro-diorite (sample N1-1), leucogabbro (N1-3), olivine-free gabbro (N1-2 and N1-4), olivine-bearing gabbro (N1-5), olivine gabbro (N1-6), plagiowehrlite and plagiodunite (N1-7), taxitic-textured rocks comprising melanotroctolite, olivine gabbro with relics of ultramafic rocks (N1-8, N1-9) and contact fine-grained gabbro (N1-10). Sulphide PGE-Cu-Ni ores occur in ultramafic (N1-7) and taxitic-textured rocks (N1-8 and N1-9), which have thickness of about 17 m, whereas the low-sulphide horizon of about 1 m thick occurs in the upper part of intrusion (N1-3). In situ U-Pb analyses of zircon from these rocks, combined with detailed study of crystal morphology and internal structure, identify four zircon populations (Malitch et al. 2012). The U-Pb ages of baddeleyite and the defined zircon populations cover a significant time span, from Late Paleozoic to Early Mesozoic (e.g., 290 ± 2.8; 261.3 ± 1.6; 245.7 ± 1.1; 236.5 ± 1.8 and 226.7 ± 0.9 Ma). The established distribution of U-Pb ages implies that crystallization of baddeleyite and zircon corresponds to several stages of protracted evolution of ultramafic-mafic magmas at deep-seated staging chambers and/or probably characterizes interaction of distinct magmas during formation

  8. A 4.43 Ga Transition from Mega-impact to Habitability Deduced from Microstructural Geochronology of Martian Zircon and Baddeleyite

    Science.gov (United States)

    Moser, D.; Reinhard, D. A.; Larson, D. J.; McCubbin, F. M.; Darling, J.; White, L. F.; Arcuri, G.; Irving, A. J.; Tait, K.; Barker, I.

    2017-12-01

    The rates at which early planetary surfaces like those of Mars and Earth transitioned to stability within the heavy bombardment epoch are poorly constrained. Here we show through analysis of the shock history of the earliest mineral remnants of Mars crust, specifically the accessory and highly refractory phases zircon and baddeleyite in martian meteorites, that the transition for Mars was relatively rapid and early. The Moon-sized impactor widely believed to have generated the martian hemispheric dichotomy, would have caused catastrophic heating, impact metamorphism and global re-surfacing by magma.This process would either destroy any primordial accessory phases through melting and vaporization, or impart micro- or nano-structural signatures of ultra-high temperature and/or pressure metamorphism on survivor crystals. We have conducted atom probe and/or correlative electron microscopy on intensely shocked and heated zircon and baddeleyite reference samples from Earth and the Moon, as well as from 4.43 Ga grains occurring as crystals and in lithic clasts in six polished surfaces of the Rabt Sbayta suite of martian polymict regolith breccias (NWA 7475, NWA 7034, NWA 7906, Rabt Sbayta 003). The martian population (n=68) shows no micro- or nano-signatures of ultra high temperature or pressure metamorphism. Instead, it exhibits mostly low-grade shock and thermal features consistent with regolith formation at 1.5 Ga and recent low pressure ( 5GPa) launch to Earth. Taken together with the time for decay of the mega-impact heat effects, as well as the 4.50 Ga age estimate for martian mantle solidification (modelled by other workers) our results indicate an early, 70 million year long transition from initiation of the hemispheric dichotomy to establishment of at least one domain of persistently stable and potentially habitable crust. The accelerated deep mantle convection prompted by mega-impact may have also increased the transport rate of volatiles to the Martian exterior

  9. Lifetime of an ocean island volcano feeder zone: constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40/39Ar age determinations, Fuerteventura, Canary Islands

    Science.gov (United States)

    Allibon, James; Ovtcharova, Maria; Bussy, Francois; Cosca, Michael; Schaltegger, Urs; Bussien, Denise; Lewin, Eric

    2011-01-01

    High-precision isotope dilution - thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 ± 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. 40Ar/39Ar amphibole dating yielded ages from 21.9 ± 0.6 to 21.8 ± 0.3, identical within errors to the U-Pb ages, despite the expected 1% theoretical bias between 40Ar/39Ar and U-Pb dates. This overlap could result from (i) rapid cooling of the intrusion (i.e., less than the 0.3 to 0.6 Ma 40Ar/39Ar age uncertainties) from closure temperatures (Tc) of zircon (699-988 °C) to amphibole (500-600 °C); (ii) lead loss affecting the youngest zircons; or (iii) excess argon shifting the plateau ages towards older values. The combination of the 40Ar/39Ar and U/Pb datasets implies that the maximum amount of time PX1 intrusion took to cool below amphibole Tc is 0.8 Ma, suggesting PX1 lifetime of 520,000 to 800,000 Ma. Age disparities among coexisting baddeleyite and zircon (22.10 ± 0.07/0.08/0.15 Ma and 21.58 ± 0.15/0.16/0.31 Ma) in a gabbro sample from the pluton margin suggest complex genetic relationships between phases. Baddeleyite is found preserved in plagioclase cores and crystallized early from low silica activity magma. Zircon crystallized later in a higher silica activity environment and is found in secondary scapolite and is found close to calcite veins, in secondary scapolite that recrystallised from plagioclase. close to calcite veins. Oxygen isotope δ18O values of altered plagioclase are high (+7.7), indicating interaction with fluids derived from host-rock carbonatites. The coexistence of baddeleyite and zircon is ascribed to interaction of the PX1 gabbro with CO2-rich carbonatite-derived fluids released during contact metamorphism.

  10. Rift magmatism on the Eurasia basin margin: U–Pb baddeleyite ages of alkaline dyke swarms in North Greenland

    DEFF Research Database (Denmark)

    Thórarinsson, Sigurjón B.; Söderlund, Ulf; Døssing, Arne

    2015-01-01

    indicate that north–south and east–west dykes are coeval. The north–south dykes reflect initial east–west rifting that led to break-up along the Gakkel Ridge and formation of the Eurasia Basin. The east–west dykes reflect local variations in the stress field associated with reactivated Palaeozoic faults...

  11. High-pressure behavior of nano titanium dioxide

    DEFF Research Database (Denmark)

    Olsen, J.S.; Gerward, Leif; Jiang, Jianzhong

    2002-01-01

    Nanocrystalline rutile Titanium dioxide has been studied by X-ray diffraction at ambient temperature up to 47.4 GPa. The material is found to transform to the monoclinic baddeleyite structure between 20 and 30 GPa, which is higher than the corresponding pressure range for bulk material. Upon...... decompression, the baddeleyite phase transforms to the alpha-PbO2 phase at about 4-2 GPa. The experimental bulk moduli are 211(7) GPa for the rutile phase, 235(16) for the baddeleyite type and 212(25) GPa for the alpha-PbO2 type phase. The results are compared with previous measurements of bulk rutile Titanium...... dioxide....

  12. Ion Microprobe U-Pb Dating of Zagami Phosphates

    Science.gov (United States)

    Sano, Y.; Koike, M.; Takahata, N.; Terada, K.

    2016-08-01

    We report U-Pb dating of Zagami phosphates using SHRIMP and NanoSIMS. A least-squares fit gives 238U-206Pb isochron age of 363 ± 120 Ma and total Pb/U age of 300 ± 84 Ma, which are older than 180 ± 7 Ma of baddeleyite of Zagami in literature.

  13. High-pressure behavior of nano titanium dioxide

    DEFF Research Database (Denmark)

    Olsen, J.S.; Gerward, Leif; Jiang, Jianzhong

    2002-01-01

    Nanocrystalline rutile Titanium dioxide has been studied by X-ray diffraction at ambient temperature up to 47.4 GPa. The material is found to transform to the monoclinic baddeleyite structure between 20 and 30 GPa, which is higher than the corresponding pressure range for bulk material. Upon deco...

  14. Compressibility and structural stability of nanocrystalline TiO2 anatase synthesized from freeze-dried precursors.

    Science.gov (United States)

    Popescu, Catalin; Sans, Juan Angel; Errandonea, Daniel; Segura, Alfredo; Villanueva, Regina; Sapiña, Fernando

    2014-11-03

    The high-pressure structural behavior of 30 nm nanoparticles of anatase TiO2 was studied under hydrostatic and quasi-hydrostatic conditions up to 25 GPa. We found that the structural sequence is not sensitive to the use of different pressure transmitting media. Anatase-type nanoparticles exhibit a phase transition beyond 12 GPa toward a baddeleyite-type structure. Under decompression this phase transition is irreversible, and a metastable columbite-type structure is recovered at ambient conditions. The bulk modulus of anatase-type nanoparticles was determined confirming that nanoparticles of TiO2 are more compressible than bulk TiO2. Similar conclusions were obtained after the determination of the bulk modulus of baddeleyite-type nanoparticles. Furthermore, axial compressibilities and the effect of pressure in atomic positions, bond distances, and bond angles are determined. Finally, a possible physical explanation for the destabilization of anatase under pressure is proposed based upon this information.

  15. Metamorphic zircon formation at the transition from gabbro to eclogite in Trollheimen-Surnadalen, Norwegian Caledonides

    Science.gov (United States)

    Beckman, Victoria; Möller, Charlotte; Söderlund, Ulf; Corfu, Fernando; Chamberlain, Kevin

    2013-04-01

    A transition zone from gabbro to eclogite via coronitic stages has been investigated at Vindøldalen in south central Norway, with the aim of linking reaction textures to metamorphic zircon growth and obtaining a direct U-Pb zircon age of the metamorphic process. Different rocks from the transition zone contain various types of zircon: I) as igneous prismatic grains; II) metamorphic polycrystalline rims and pseudomorphs after baddeleyite, and III) tiny (> 10µm) bead-like zircon grains associated with a) oxidation and b) resorption of Ti-Fe oxides. During progressive transformation from gabbro to eclogite, titanomagnetite (magnetite with ilmenite lamellae) was oxidised to titanohematite (hematite + ilmenite); at advanced stages of recrystallization to eclogite, rutile was produced at the expense of Fe-Ti oxide. Textural relations suggests that the FeTi-oxides were the main source of Zr. Subsolidus liberation of Zr and formation of zircon beads took place by oxidation of titanomagnetite during fluid-assisted metamorphism in undeformed corona gabbro, and by resorption of FeTi-oxide in undeformed and strongly deformed rock domains that were recrystallized to eclogite. Secondary ionization mass spectrometry (SIMS) and Thermal ionization mass spectrometry (TIMS) were used to obtain U-Pb ages of zircon and baddeleyite. Magmatic baddeleyite yields a TIMS age of 1.46 Ga dating igneous crystallisation, whereas the SIMS age for baddeleyite and magmatic zircon from the same gabbro is slightly younger. Bead-type metamorphic zircon from eclogite gives an age of 425±10 Ma (TIMS), and dates directly the metamorphic transition from gabbro to eclogite in the upper basement of the Lower Allochthon in the south-central Scandinavian Caledonides. The metamorphic zircon age does not necessarily date the peak metamorphic temperature, but reflects fluid-induced reactions and oxidation of primary phases.

  16. Uranium prospecting in alkaline mountain chimneys of Serra Negra and Salitre - Minas Gerais, Brasil

    International Nuclear Information System (INIS)

    Souza Filho, J.G.C.

    1974-01-01

    The occurence of radioactive minerals such as apatite and pyrochlore, in the alkaline chimneys of Serra Negra and Salitre (Minas Gerais, Brazil), is discussed. Also mentioned are other minerals of interest associated with the alkaline magma such as columbite, fluorite, monazite, zircon, baddeleyite, etc, which in favourable conditions may occur in deposits of great economical value, and which may present high contents of rare earths, thorium and uranium

  17. Naturally occurring crystalline phases: analogues for radioactive waste forms

    International Nuclear Information System (INIS)

    Haaker, R.F.; Ewing, R.C.

    1981-01-01

    Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemistry, occurrence, alteration and radiation effects are described. A selected bibliography for each phase is included

  18. Naturally occurring crystalline phases: analogues for radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Haaker, R.F.; Ewing, R.C.

    1981-01-01

    Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemistry, occurrence, alteration and radiation effects are described. A selected bibliography for each phase is included.

  19. Zirconium oxide deposits (ZrO2) and titanium oxide (TiO2) on 304l stainless steel

    International Nuclear Information System (INIS)

    Davila N, M. L.

    2015-01-01

    This research project aims to carry out the surface and electrochemical characterization to obtain the optimum conditions of the hydrothermal deposits of zirconium oxide ZrO 2 (baddeleyite) and titanium oxide TiO 2 (anatase and rutile phases) on 304l stainless steel, simulating an inhibiting protective layer. 304l steel specimens were cut, pre-oxidized in water at a temperature of 288 degrees Celsius and 8 MPa, similar to those of a typical BWR conditions. From the titanium oxide anatase crystalline phase, the rutile phase was obtained by a heat treatment at 1000 degrees Celsius. The Sigma-Aldrich pre-oxidized powders and steel 304l were characterized using techniques of X-ray diffraction, scanning electron microscopy, X-ray dispersive energy, chemical mapping and Raman spectrometry. The pre-oxidized steel has two oxide layers, an inner layer with nano metric crystals and another outer of larger crystals to 1μm, with the formation of hematite and magnetite, this predominating. The surface that contacted the sample holder has larger crystals. Hydrothermal deposits were carry out from suspensions of 10, 100 and 1000 ppm, of the crystal phases of anatase, rutile and baddeleyite, on the pre-oxidized steel at a temperature of 150 degrees Celsius for 2 and 7 days, samples were analyzed by X-ray diffraction, scanning electron microscopy, X-ray dispersive energy, Raman spectrometry and Tafel polarization. The suspension to 1000 ppm for 7 days coated surface most; the baddeleyite deposit is noticed more homogeneous than anatase and rutile. The deposit is favored when hematite and magnetite crystals are larger. The chemical mapping on deposits show that even after being immersed in water to 288 degrees Celsius during 30 days, the deposits are still present although a loss is observed. A reference electrode was assembled to conduct electrochemical tests of Tafel able to withstand a temperature of 288 degrees Celsius and pressure of 8 MPa. The baddeleyite deposit presented

  20. Zirconium oxide deposits (ZrO{sub 2}) and titanium oxide (TiO{sub 2}) on 304l stainless steel; Depositos de oxido de circonio (ZrO{sub 2}) y oxido de titanio (TiO{sub 2}) sobre acero inoxidable 304L

    Energy Technology Data Exchange (ETDEWEB)

    Davila N, M. L.

    2015-07-01

    This research project aims to carry out the surface and electrochemical characterization to obtain the optimum conditions of the hydrothermal deposits of zirconium oxide ZrO{sub 2} (baddeleyite) and titanium oxide TiO{sub 2} (anatase and rutile phases) on 304l stainless steel, simulating an inhibiting protective layer. 304l steel specimens were cut, pre-oxidized in water at a temperature of 288 degrees Celsius and 8 MPa, similar to those of a typical BWR conditions. From the titanium oxide anatase crystalline phase, the rutile phase was obtained by a heat treatment at 1000 degrees Celsius. The Sigma-Aldrich pre-oxidized powders and steel 304l were characterized using techniques of X-ray diffraction, scanning electron microscopy, X-ray dispersive energy, chemical mapping and Raman spectrometry. The pre-oxidized steel has two oxide layers, an inner layer with nano metric crystals and another outer of larger crystals to 1μm, with the formation of hematite and magnetite, this predominating. The surface that contacted the sample holder has larger crystals. Hydrothermal deposits were carry out from suspensions of 10, 100 and 1000 ppm, of the crystal phases of anatase, rutile and baddeleyite, on the pre-oxidized steel at a temperature of 150 degrees Celsius for 2 and 7 days, samples were analyzed by X-ray diffraction, scanning electron microscopy, X-ray dispersive energy, Raman spectrometry and Tafel polarization. The suspension to 1000 ppm for 7 days coated surface most; the baddeleyite deposit is noticed more homogeneous than anatase and rutile. The deposit is favored when hematite and magnetite crystals are larger. The chemical mapping on deposits show that even after being immersed in water to 288 degrees Celsius during 30 days, the deposits are still present although a loss is observed. A reference electrode was assembled to conduct electrochemical tests of Tafel able to withstand a temperature of 288 degrees Celsius and pressure of 8 MPa. The baddeleyite deposit

  1. <報文>レアメタル資源に関する研究(I) : ジルコニウム資源としてのPocos de Caldas, Brasil産カルダサイト

    OpenAIRE

    佐藤, 修彰; 伊藤, 良雅; 南條, 道夫

    1986-01-01

    The zirconium deposit of the Pocos de Caldas Plateau is north of Sa^^?o Paulo, Brasil, on the boundary between the States of Minas Gerais and Sa^^?o Paulo. The zirconium ore was formed as a mixture of baddeleyite (ZrO_2) and zircon (ZrSiO_4) which was identified as caldasite from the microscopic, X-ray and electron microprobe studies. This ore also contained a high content of uranium and thorium oxides, enough for nuclear fuel resources from the γ-ray spectrometry. The ore shows stable behavi...

  2. Superficial and electrochemical study of stainless steel 304l with an inhibitory protective coating (TiO{sub 2} and ZrO{sub 2}); Estudio superficial y electroquimico de acero inoxidable 304L con una capa protectora inhibidora (TiO{sub 2} y ZrO{sub 2})

    Energy Technology Data Exchange (ETDEWEB)

    Davila N, M. L.; Contreras R, A.; Arganis J, C. R., E-mail: aida.contreras@inin.gob.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2014-10-15

    The degradation mechanisms in the boiling water reactors (BWR) have been an alert focus for owners, especially the cracking by stress corrosion cracking (SCC), therefore different techniques have been studied to inhibit this problem inside which is the water injection of hydrogen feeding (HWC, Hydrogen Water Chemistry), together with the noble metals injection (NMCA, Nobel Metal Chemical Addition) and the ceramic materials injection that form an inhibitory protective coating (Ipc). In this work the Ipc was simulated, for which were carried out hydro-thermals deposits starting from suspensions of 1000 ppm of zirconium oxide in its crystalline phase baddeleyite and titanium oxides in its anatase and rutile phases, on test tubes of stainless steel 304l previously rusty under simulated conditions of pressure and temperature of a BWR (288 C and 8 MPa). The superficial characterization was realized by scanning electron microscopy, energy-dispersive of X-ray and X-ray diffraction. The capacity to mitigate the corrosion was studied with the electrochemical technique of Tafel polarization (288 C and 8 MPa). The steel presents the formation of two oxide coatings formed by magnetite and hematite. The baddeleyite presents a deposit more thick and homogeneous it also presents the most negative electrochemical potential of corrosion, what indicates that it has the bigger capacity to mitigate the SCC. (Author)

  3. Superficial and electrochemical study of stainless steel 304l with an inhibitory protective coating (TiO2 and ZrO2)

    International Nuclear Information System (INIS)

    Davila N, M. L.; Contreras R, A.; Arganis J, C. R.

    2014-10-01

    The degradation mechanisms in the boiling water reactors (BWR) have been an alert focus for owners, especially the cracking by stress corrosion cracking (SCC), therefore different techniques have been studied to inhibit this problem inside which is the water injection of hydrogen feeding (HWC, Hydrogen Water Chemistry), together with the noble metals injection (NMCA, Nobel Metal Chemical Addition) and the ceramic materials injection that form an inhibitory protective coating (Ipc). In this work the Ipc was simulated, for which were carried out hydro-thermals deposits starting from suspensions of 1000 ppm of zirconium oxide in its crystalline phase baddeleyite and titanium oxides in its anatase and rutile phases, on test tubes of stainless steel 304l previously rusty under simulated conditions of pressure and temperature of a BWR (288 C and 8 MPa). The superficial characterization was realized by scanning electron microscopy, energy-dispersive of X-ray and X-ray diffraction. The capacity to mitigate the corrosion was studied with the electrochemical technique of Tafel polarization (288 C and 8 MPa). The steel presents the formation of two oxide coatings formed by magnetite and hematite. The baddeleyite presents a deposit more thick and homogeneous it also presents the most negative electrochemical potential of corrosion, what indicates that it has the bigger capacity to mitigate the SCC. (Author)

  4. Rare earth element carriers in the Shergotty meteorite and implications for its chronology

    Science.gov (United States)

    Lundberg, Laura L.; Crozaz, Ghislaine; Zinner, Ernst; Mckay, Gordon

    1988-01-01

    This paper reports on the results of ion-probe measurements of REE concentrations in individual grains of the Shergotty meteorite. The phases analyzed included whitlockite, apatite, baddeleyite, augite, pigeonite, maskelynite, and K-rich glass; the whitlockite and apatite phases were also analyzed for U. Results indicate that whitlockite contains the bulk of the REE in Shergotty, with no evidence for distinct light-REE patterns in texturally different whitlockites. The results on the evolution of the REE abundances in the Shergotty late-stage interstitial melt, inferred from the analysis of whitlockite, are consistent with closed system crystallization. No metasomatic alteration is required to explain the REE data. It is concluded that there is no compelling reason to attribute chronological significance to the Sm-Nd array, as was done by Jagoutz and Waenke (1986).

  5. Mineralogy, Petrology and Oxygen Fugacity of the LaPaz Icefield Lunar Basaltic Meteorites and the Origin of Evolved Lunar Basalts

    Science.gov (United States)

    Collins, S. J.; Righter, K.; Brandon, A. D.

    2005-01-01

    LAP 02205 is a 1.2 kg lunar mare basalt meteorite found in the Lap Paz ice field of Antarctica in 2002 [1]. Four similar meteorites were also found within the same region [1] and all five have a combined mass of 1.9 kg (LAP 02224, LAP 02226, LAP 02436 and LAP 03632, hereafter called the LAP meteorites). The LAP meteorites all contain a similar texture, mineral assemblage, and composition. A lunar origin for these samples comes from O isotopic data for LAP 02205 [1], Fe/Mn ratios of pyroxenes [1-5], and the presence of distinct lunar mineralogy such as Fe metal and baddeleyite. The LAP meteorites may represent an area of the Moon, which has never been sampled by Apollo missions, or by other lunar meteorites. The data from this study will be used to compare the LAP meteorites to Apollo mare basalts and lunar basaltic meteorites, and will ultimately help to constrain their origin.

  6. Purification of zirconium concentrates

    International Nuclear Information System (INIS)

    Brown, A.E.P.

    1976-01-01

    A commercial grade ZrO 2 and an ammonium uranate (yellow cake) are obtained from the caldasito ore processing. This ore is found in the Pocos de Caldas Plateau, State of Minas Gerais, Brazil. Caldasito is an uranigerous zirconium ore, a mixture of zircon and baddeleyite and contains 60% ZrO 2 and 0,3% U 3 O 8 . The chemical opening of the ore was made by alkaline fusion with NaOH at controlled temperature. The zirconium-uranium separation took place by a continuous liquid-liquid extraction in TBP-varsol-HNO 3 -H 2 O system. The raffinate containing zirconium + impurities (aluminium, iron and titanium) was purified by an ion exchange operation using a strong cationic resin [pt

  7. Zirconium

    Science.gov (United States)

    Bedinger, G.M.

    2013-01-01

    Zirconium is the 20th most abundant element in the Earth’s crust. It occurs in a variety of rock types and geologic environments but most often in igneous rocks in the form of zircon (ZrSiO4). Zircon is recovered as a coproduct of the mining and processing of heavy mineral sands for the titanium minerals ilmenite and rutile. The sands are formed by the weathering and erosion of rock containing zircon and titanium heavy minerals and their subsequent concentration in sedimentary systems, particularly in coastal environments. A small quantity of zirconium, less than 10 kt/a (11,000 stpy), compared with total world production of 1.4 Mt (1.5 million st) in 2012, was derived from the mineral baddeleyite (ZrO2), produced from a single source in Kovdor, Russia.

  8. High-pressure synchrotron studies on TiO sub 2 -II nanocrystallite doped with SnO sub 2

    CERN Document Server

    Luo, W; Zou Guang Tian; Mao Ho Kwang; Wang, Z C; Wang, Y

    2002-01-01

    We have studied the high-pressure and high-temperature behaviour of alpha-PbO sub 2 -type TiO sub 2 -SnO sub 2 (5 mol%) nanocomposite up to 62.3 GPa and 1700 K in a laser-heated diamond-anvil cell by means of synchrotron energy-dispersive x-ray diffraction. We found that it transforms to the baddeleyite phase at 19.4 GPa at room temperature. This phase was stable up to about 40 GPa. At 62.3 GPa and 1700 K, the diffraction pattern showed that there exists another nonquenchable phase. We discussed the mechanisms for these high-pressure transformations in alpha-PbO sub 2 -type TiO sub 2 -SnO sub 2 (5 mol%) nanocomposite.

  9. Assessment of exposures to ionizing radiation in industries and activities implementing raw materials which naturally contain radionuclides and which are not used because of their radioactive properties. Assessment of the 25. of May 2005 Order related to these activities

    International Nuclear Information System (INIS)

    2009-12-01

    This report proposes an assessment of the exposure of workers and of population to reinforced natural radioactivity associated to some particular professional activities, i.e. activities where raw materials which are used, are naturally radioactive, for example: coal combustion in thermal power plants, ore processing (tin, aluminium, copper, titanium, niobium, bismuth, thorium), production of refractory ceramics, production or use of thorium compounds, zircon or baddeleyite production, and so on. After a presentation of the French national regulation, the report gives an assessment of its application through different measurements or surveys, notably dosimetry performed on workers or population exposure measurements, or some waste management activities. It discusses the evolution opportunities of this regulation, either in the French framework or at the European level

  10. On the rutile alpha-PbO"2-type phase boundary of TiO"2

    DEFF Research Database (Denmark)

    Olsen, J.S.; Gerward, Leif; Jiang, Jianzhong

    1999-01-01

    The high-pressure, high-temperature phase quilibria of TiO"2 have been studied with special emphasis on the rutile and alpha-PbO"2-type phases. It is found that the phase boundary, when plotted in a pressure-temperature diagram, changes from having a negative to having a positive slope...... with increasing temperature at about 6GPa and 850^oC. For nanophase material, the phase boundary is shifted towards lower pressure. The room-temperature bulk moduli are 210(120)GPa, 258(8)GPa and 290(20)GPa for rutile, the alpha-PbO"2-type phase and the baddeleyite-type phase, respectively....

  11. Bixbyite-type phases in the system Ta-Zr-O-N

    Energy Technology Data Exchange (ETDEWEB)

    Luedtke, Tobias; Orthmann, Steven; Lerch, Martin [Technische Univ. Berlin (Germany). Inst. fuer Chemie

    2017-06-01

    Phase-pure tantalum/zirconium oxide nitrides and nitrides were synthesized by the ammonolysis of amorphous oxide precursors. The nitrogen-rich oxide nitrides with variable anion composition and the nitride TaZrN3 crystallize in the cubic bixbyite-type structure (space group Ia3). The nitrogen content of these compounds has a significant influence on the cell parameters, the atomic positions, and the optical band gap. The results extend the already well-studied Ta-Zr-O-N system by new oxide nitrides in addition to the already known baddeleyite- and anosovite-type phases. TaZrN{sub 3} can be considered as a thermodynamically stable ternary variant of metastable Ta{sub 2}N{sub 3}.

  12. 3D mineralogical mapping of the Kovdor phoscorite-carbonatite complex (Russia)

    Science.gov (United States)

    Mikhailova, Julia A.; Kalashnikov, Andrey O.; Sokharev, Victor A.; Pakhomovsky, Yakov A.; Konopleva, Nataly G.; Yakovenchuk, Victor N.; Bazai, Ayya V.; Goryainov, Pavel M.; Ivanyuk, Gregory Yu.

    2016-01-01

    The Kovdor baddeleyite-apatite-magnetite deposit in the Kovdor phoscorite-carbonatite pipe is situated in the western part of the zoned alkali-ultrabasic Kovdor intrusion (NW part of the Fennoscandinavian shield; Murmansk Region, Russia). We describe major intrusive and metasomatic rocks of the pipe and its surroundings using a new classification of phoscorite-carbonatite series rocks, consistent with the IUGS recommendation. The gradual zonation of the pipe corresponds to the sequence of mineral crystallization (forsterite-hydroxylapatite-magnetite-calcite). Crystal morphology, grain size, characteristic inclusions, and composition of the rock-forming and accessory minerals display the same spatial zonation pattern, as do the three minerals of economic interest, i.e. magnetite, hydroxylapatite, and baddeleyite. The content of Sr, rare earth elements (REEs), and Ba in hydroxylapatite tends to increase gradually at the expense of Si, Fe, and Mg from early apatite-forsterite phoscorite (margins of the pipe) through carbonate-free, magnetite-rich phoscorite to carbonate-rich phoscorite and phoscorite-related carbonatite (inner part). Magnetite displays a trend of increasing V and Ca and decreasing Ti, Mn, Si, Cr, Sc, and Zn from the margins to the central part of the pipe; its grain size initially increases from the wall rocks to the inner part and then decreases towards the central part; characteristic inclusions in magnetite are geikielite within the marginal zone of the phoscorite-carbonatite pipe, spinel within the intermediate zone, and ilmenite within the inner zone. The zoning pattern seems to have formed due to both cooling and rapid degassing (pressure drop) of a fluid-rich magmatic column and subsequent pneumatolytic and hydrothermal processes.

  13. Paleomagnetism and geochronological studies on a 450 km long 2216 Ma dyke from the Dharwar craton, southern India

    Science.gov (United States)

    Nagaraju, E.; Parashuramulu, V.; Kumar, Anil; Srinivas Sarma, D.

    2018-01-01

    Paleomagnetic and geochronological studies were carried out on a ∼ 450 km long (from 17 sites) N-S striking Paleoproterozoic dyke swarm exposed along a natural crustal cross section of about 10 km (increasing from North to South) in the Dharwar Craton, to study the characteristics of paleomagnetism and geochronology in vertical dimension. U-Pb/Pb-Pb dating on baddeleyite gives a crystallisation age of 2216.0 ± 0.9 Ma for long dyke AKLD. Paleomagnetic data from this well dated ∼ 2216 Ma dyke swarm in Dharwar Craton are of excellent quality. High coercivity and high blocking temperature components are carried by single domain magnetite and show dual polarity remanence directions. Combined normal and reverse polarity remanences on AKLD and other N-S dykes define the most reliable paleomagnetic pole for ∼ 2216 Ma at latitude 36°S and longitude 312°E (A95 = 7°). Though paleomagnetic data is unavailable on other N-S dykes below the Cuddapah basin, high precision geochronology suggest that they are of similar age within errors. Though there is a variation in the crustal depth of Dharwar craton from north to south, consistent Pb-Pb/U-Pb baddeleyite geochronology and paleomagnetic studies along the AKLD established its continuity and preservation along its entire strike length. The virtual geomagnetic poles of these sites confirm a stable remanence and are almost identical to the previously reported paleomagnetic pole and also supported by positive reversal test. Positive paleomagnetic reversal test on these dykes signify that the remanent magnetization is primary and formed during initial cooling of the intrusions. Updated apparent polar wander path of Dharwar craton indicates relatively low drift rate during 2.21-2.08 Ga interval. Magnetogranulometry and SEM studies show that remanent magnetization in this dyke was carried by single domain magnetite residing within silicate minerals.

  14. Local environment of zirconium in nuclear gels studied by XAS

    International Nuclear Information System (INIS)

    Pelegrin, E.; Ildefonse, Ph.; Calas, G.; Ricol, St.; Flank, A.M.

    1997-01-01

    During lixiviation experiments, nuclear gels are formed and heavy metals are retained. In order to understand this retardation mechanisms, we performed an analysis of the local environment of Zr in parent glasses and derived alteration gels both at the Zr-L II,III , and Zr-K edges. Calibration of the method was conducted through the analysis of model compounds with known coordination number (CN): catapleite Na 2 ZrSi 3 O 9 ,2H 2 O (CN=6), baddeleyite ZrO 2 (CN=7) and zircon SiZrO 4 (CN=8). Nuclear glasses (R7T7, and a simplified nuclear glass V 1) and gels obtained at 90 deg C, with leaching times from 7 to 12 months and with solution renewal. were also investigated (GR7T7R and GV1). Zr-L II,III XANES spectra evidenced that zirconium is 6-fold coordinated in R7T7 and V1 nuclear glasses. For GR7T7R and GV1 gels, Zr local environment is significantly changed, and a mixture of CN (6 and 7J has been evidenced. Quantitative structural results were derived from EXAFS analysis at Zr-K edge. In parent glasses, derived Zr-O distance is 2.10±0.01 10 -10 m, and is in the range Zr-O distances for octahedral coordination in model compounds. In both gels studied, Zr-O distances increase significantly up to 2.15 ±0.01 10 -10 m. This distance is close to that known in baddeleyite (2,158 10 -10 m). A better understanding of the Zr retention mechanism has to be made by studying the second neighbors contributions. (authors)

  15. The microstructure of zircon and its influence on the age determination from Pb/U isotopic ratios measured by ion microprobe

    Science.gov (United States)

    McLaren, A. C.; Gerald, J. D. Fitz; Williams, I. S.

    1994-01-01

    TEM observations of a large, high-U, Sri Lankan, gem-gravel zircon suggest that certain microstructural features are associated with discordant Pb/U ages measured in this crystal with the SHRIMP I ion microprobe. Some of the growth bands in the rim of the crystal are optically isotropic and the microstructure of one such band (ca 100 μm wide; designated I) has been compared with the microstructure of the adjacent optically anisotropic regions (designated A). The I-band has a significantly higher U and Pb content, and its electron diffraction pattern of very diffuse rings indicates the absence of periodic atomic arrangements. A-regions consist of parallel-oriented zircon crystallites (ca 10 nm in size) in a matrix with the same characteristics as the I-band. The volume fraction of crystalline zircon in any given growth band correlates (inversely) with the measured birefringence and is taken to be an indication of the degree of radiation damage. Annealing in air at temperatures T zirconia which is present as randomly oriented crystallites (ca 10 nm in size), presumably in association with silica glass, in both the I-band and A-regions. However, there is no significant growth of the zircon crystallites in A-regions. After annealing at 1250°C, the zirconia crystallites in the I-band transform to baddeleyite. The crystallites are ca 100 nm in size and the silica glass phase is easily identified. However, the A-regions have recrystallized to a zircon single crystal with precipitates of baddeleyite (ca 40 nm in size) and, presumably, some silica glass. The 207Pb /206Pb ages determined with the ion microprobe are essentially independent of the microstructure and average 552 Ma. However, the Pb/U ages are all reverse discordant (that is, greater than 552 Ma). The discordance (defined as the measured value of 206Pb /238U divided by the value expected at 552 Ma) is about 1.1 in most specimens annealed up to 900°C, but as high as 3.5 in the I-band after annealing at 1250

  16. REE-substituted Ca-free zirconolites

    International Nuclear Information System (INIS)

    Stefanovsky, S.V.; Chernyavskaya, N.E.; Ochkin, A.V.; Yudintsev, S.V.

    2002-01-01

    Previously we found zirconolite with composition (Gd 0.90 La 0.10 )(Zr 0.91 Ce 0.13 ) (Ti 1.20 Al 0.69 )O 7 in one of the ceramics designed for immobilization of REE-actinide HLW fraction. In this work we studied REEZrTiAlO 7 zirconolites with REE = La, Ce, Pr, Nd, Sm, Gd, Tb, and Y. To obtain the samples, the oxide mixtures were milled, compacted into pellets at 200 MPa and sintered at 1450 deg C or melted at 1550 deg C in air. To convert Ce (IV) to Ce (III), one test was performed in reducing conditions (carbon was introduced in batches). The ceramics were examined by X-ray diffraction (XRD) and by scanning and transmission electron microscopy (SEM, TEM). The XRD data revealed that the La-, Ce-, Pr-, and Nd-bearing samples were not single-phase ceramics. The La-bearing sample was composed of a major perovskite-type phase and a minor baddeleyite. The Ce-bearing samples consisted of major pyrochlore, cerianite-zirconia based cubic solid solution as a second in abundance phase, and minor zirconolite. The Pr-bearing ceramic contained major baddeleyite and a perovskite-type phase, and minor pyrochlore. In the Nd-, Sm-, Gd-, Tb-, and Y-bearing samples, zirconolite was predominant. Rare grains of REE-stabilized zirconia (fianite) were found by SEM in the Nd-, Sm, and Y-bearing ceramics. The Gd- and Tb-bearing samples were single phase. The average zirconolite formulas were Sm 1.06 Zr 1.07 Ti 1.00 Al 0.86 O 7 , Gd 1.01 Zr 1.05 Ti 0.98 Al 0.95 O 7 , Tb 0.93 Zr 1.09 Ti 1.08 Al 0.85 O 7 , and Y 1.05 Zr 1.03 Ti 1.03 Al 0.87 O 7 , hence, close to the specified zirconolite formula within the experimental error. XRD patterns of the Tb- and Y-bearing zirconolites are typical of zirconolite-2M variety. XRD patterns of the Nd-, Sm-, and Gd-bearing zirconolites differ from patterns typical of 2M, 3T, and 3O varieties known from reference data. The TEM study revealed a probable tetragonal symmetry of the zirconolite lattice on electron diffraction pattern

  17. Magnetic studies and U Pb geochronology of the Uruguayan dyke swarm, Rio de la Plata craton, Uruguay: paleomagnetic and economic implications

    Science.gov (United States)

    Halls, Henry C.; Campal, Nestor; Davis, Don W.; Bossi, Jorge

    2001-09-01

    A U-Pb age on baddeleyite of 1790±5 Ma has been obtained from a single dyke of the Uruguayan tholeiitic dyke swarm from the Rio de la Plata craton. Palaeomagnetic results from this and 10 other dykes yield two components, one (A) has the following paleomagnetic parameters: declination=12°, inclination=-16°, α95=7°, latitude of paleopole=61°, longitude=-31°, dp=4°, dm=7°, paleolatitude=-8°, whereas another (B), about 20° steeper, has a direction closer to the present Earth's field direction in Uruguay. Neither magnetisation is considered primary, although the A component may represent a composite between B and a primary component. A field test for the primary nature of the remanences was inconclusive, and no primary pole positions of similar age from other South American cratons are available for comparison. The magnetic results demonstrate that darker-coloured andesite dykes that are sought for facing and monument stone (as 'black granite') can be easily differentiated from more andesi-basaltic, lighter coloured, less valuable dykes of the same swarm, using aeromagnetic data. The results suggest that a high resolution airborne magnetic survey could constitute an important exploration tool for the Uruguayan 'black granite' industry.

  18. The physical and mechanical properties and local deformation micromechanisms in materials with different dependence of hardness on the depth of print

    Science.gov (United States)

    Golovin, Yu. I.; Tyurin, A. I.; Aslanyan, E. G.; Pirozhkova, T. S.; Vasyukov, V. M.

    2017-09-01

    The size hardness effects are studied via the micro- and nanoindentation methods over the wide range of the depth of print h (from dozens of nanometers to several dozen micrometers) for several classes of materials, such as ionic and covalent single crystals (sapphire, silicon, lithium fluoride); metals (single-crystal Al, polycrystalline Cu, Ni, and Nb); ceramics (high-strength nanostructured TZP-ceramic based on the natural zirconium dioxide-baddeleyite mineral); amorphous materials (fused quartz); and polymers (polycarbonate and polytetrafluoroethylene). As is shown, some of them possess severe size hardness effects, whereas the others reveal the weak ones or even a lack of these effects. The thermoactivation analysis is implemented, as well, and the activating and energy characteristics of local deformation processes induced by an indenter are compared with the dominant plasticity micromechanisms of the studied materials at different stages of the print formation and with the size peculiarities. The materials with low hardness coefficients and meeting the requirements of ISO 14577 and GOST R 8.748-2011 standards in the nanohardness measurements are highlighted, as well. In the established load ranges, these materials are the promising candidates for their use as reference samples, which are designed to ensure the uniformity of the hardness measurements at the nano- and microscales, as well as for calibrating and testing the nanoindentometers.

  19. Study on fused/cast AZS refractories for deployment in vitrification of radioactive waste effluents

    Science.gov (United States)

    Sengupta, Pranesh; Mishra, R. K.; Soudamini, N.; Sen, D.; Mazumder, S.; Kaushik, C. P.; Ajithkumar, T. G.; Banerjee, K.

    2015-12-01

    'Fused/cast Al2O3-ZrO2-SiO2 (FC-AZS)' is being considered as 'glass contact refractory' within ceramic melters, to be used for nuclear waste immobilization. Microstructural analyses reveal random distributions of baddeleyite (ZrO2) within aluminosilicate (Al2SiO5) matrix. 27Al and 29Si NMR data suggest that within aluminosilicate matrix Al occurs in both 4- and 6-fold co-ordinations whereas Si prefers a 4-fold environment. Polydispersity of pores has been studied with small-angle neutron scattering (SANS) technique. Corrosion rates of FC-AZS within 6 M HNO3, simulated wastes (500 h exposure), and borosilicate melt (975 °C, 800 h exposure) are found to be 0.38 × 103 μmy-1, 0.13 × 103 μmy-1 and 4.75 × 103 μmy-1 respectively. A comparison of chemical interaction data clearly suggests that FC-AZS exhibits better chemical durability than AZC refractory (Al2O3-ZrO2-Cr2O3, also used for similar purpose). Thermal cycling studies indicate that FC-AZS retains structural integrity (including compressive strength and density) even up to 20 cycles.

  20. Approach of automatic 3D geological mapping: the case of the Kovdor phoscorite-carbonatite complex, NW Russia.

    Science.gov (United States)

    Kalashnikov, A O; Ivanyuk, G Yu; Mikhailova, J A; Sokharev, V A

    2017-07-31

    We have developed an approach for automatic 3D geological mapping based on conversion of chemical composition of rocks to mineral composition by logical computation. It allows to calculate mineral composition based on bulk rock chemistry, interpolate the mineral composition in the same way as chemical composition, and, finally, build a 3D geological model. The approach was developed for the Kovdor phoscorite-carbonatite complex containing the Kovdor baddeleyite-apatite-magnetite deposit. We used 4 bulk rock chemistry analyses - Fe magn , P 2 O 5 , CO 2 and SiO 2 . We used four techniques for prediction of rock types - calculation of normative mineral compositions (norms), multiple regression, artificial neural network and developed by logical evaluation. The two latter became the best. As a result, we distinguished 14 types of phoscorites (forsterite-apatite-magnetite-carbonate rock), carbonatite and host rocks. The results show good convergence with our petrographical studies of the deposit, and recent manually built maps. The proposed approach can be used as a tool of a deposit genesis reconstruction and preliminary geometallurgical modelling.

  1. U-Pb zircon geochronology and evolution of some Adirondack meta-igneous rocks

    Science.gov (United States)

    Mclelland, J. M.

    1988-01-01

    An update was presented of the recent U-Pb isotope geochronology and models for evolution of some of the meta-igneous rocks of the Adirondacks, New York. Uranium-lead zircon data from charnockites and mangerites and on baddeleyite from anorthosite suggest that the emplacement of these rocks into a stable crust took place in the range 1160 to 1130 Ma. Granulite facies metamorphism was approximately 1050 Ma as indicated by metamorphic zircon and sphene ages of the anorthosite and by development of magmatitic alaskitic gneiss. The concentric isotherms that are observed in this area are due to later doming. However, an older contact metamorphic aureole associated with anorthosite intrusion is observed where wollastonite develops in metacarbonates. Zenoliths found in the anorthosite indicate a metamorphic event prior to anorthosite emplacement. The most probable mechanism for anorthosite genesis is thought to be ponding of gabbroic magmas at the Moho. The emplacement of the anorogenic anorthosite-mangerite-charnockite suite was apparently bracketed by compressional orogenies.

  2. The structure of ZrO{sub 2} phases and deviltrification processes in a Ca-Zr-Si-O-based glass ceramic: a combined a-XRD and XAS study

    Energy Technology Data Exchange (ETDEWEB)

    Meneghini, C. [Rome-3 Univ. (Italy). Dipt. di Fisica; INFM-OGG, 38 - Grenoble (France); Mobilio, S. [Rome-3 Univ. (Italy). Dipt. di Fisica; Lusvarghi, L.; Bondioli, F.; Ferrari, A.M.; Manfredini, T.; Siligardi, C. [Dipt. Ingegneria dei Materiali e dell' Ambiente, Modena (Italy)

    2004-12-01

    The structure of Zr atomic environment in a CaO-ZrO{sub 2}-Si{sub 2} glass ceramic as a function of thermal treatments has been studied, combining X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and anomalous XRD (a-XRD) techniques. The analysis of XRD patterns demonstrates that the devitrification process proceeds through the partial segregation of Zr-depleted phases (wollastonite-like) and Zr-rich phases (Zr oxides). The XAS and a-XRD measurements at the Zr K-edge have been exploited in order to obtain a closer insight into the atomic structure around the Zr atoms. In the as-quenched glass the Zr atom is sixfold coordinated to O atoms in an amorphous environment rich in Ca and Si. Thermal treatment firstly (T=1273-1323 K) causes partial segragation of Zr in the form of an oxide with a tetragonal zirconia (t-ZrO{sub 2}) crystalline structure. Raising the temperature (T=1373 K) causes the formation of ZrO{sub 2} crystallites in the monoclinic crystallographic phase (baddeleyite, m-ZrO{sub 2}). Analysis of the XAS data shows that a considerable amount of Zr remains in an amorphous calcium silicate phase. (orig.)

  3. A Sulfate Aerosol Trigger for the Sturtian Neoproterozoic Snowball Event

    Science.gov (United States)

    Wordsworth, R. D.; Macdonald, F. A.

    2017-12-01

    Despite the dominance of the carbon cycle in determining the evolution of Earth's climate in general, certain events defy easy explanation via atmospheric CO2 changes alone. Here we discuss the particular role that transient planetary albedo changes via sulfate aerosol formation can play in major climate transitions. Specifically, we propose that SO2 outgassing associated with the eruption of the Franklin Large Igneous Province (LIP) led to the first Neoproterozoic Snowball event, the Sturtian, 716 Ma. We summarize U/Pb zircon and baddeleyite dating indicating the synchronicity of the Franklin eruptions and the onset of the Sturtian, and paleomagnetic data indicating that the Franklin erupted close to the equator. We then discuss in detail the modeling we have performed of eruption rate, the plume height achieved during basaltic fissure volcanism, the chemistry and microphysics of sulfate aerosol formation, and the dependence of aerosol longwave and shortwave radiative effects on atmospheric loading, particle size and surface albedo. We discuss the critical importance of the latitude of eruption, the tropopause height, and ocean dynamics in determining the strength and sign of aerosol radiative forcing. We finish by comparing the Franklin event with other LIP emplacement events in Earth history and make suggestions for future modeling.

  4. Crystallographic shear of polymorphic TiO{sub 2} nanocondensates with enhanced Cr{sub 2}O{sub 3} dissolution via pulsed laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chun-Han; Huang, Chang-Ning [National Sun Yat-sen University, Department of Materials and Optoelectronic Science, Taiwan (China); Chen, Shuei-Yuan [I-Shou University, Department of Mechanical and Automation Engineering, Taiwan (China); Shen, Pouyan, E-mail: pshen@mail.nsysu.edu.tw [National Sun Yat-sen University, Department of Materials and Optoelectronic Science, Taiwan (China)

    2011-09-15

    TiO{sub 2} nanoparticles with enhanced solid solution of Cr up to 16 wt% in polymorphs of rutile, anatase, brookite, {alpha}-PbO{sub 2}-type, and occasionally baddeleyite-type were synthesized via pulse laser ablation on ceramic TiO{sub 2} target dissolved with Cr{sub 2}O{sub 3} or clamped Cr/Ti plates in air. Analytical electron microscopic observations indicated these nanocondensates have prevalent crystallographic shear (CS) along specific planes to form superstructures. The rutile type typically shows (100) and (010) CS besides the conventional ones rotating about the [111] zone axis as reported for ambient samples. The CS planes are parallel to (001) for anatase, (001) and (1-bar 10) for brookite, whereas (001) and {l_brace}1 3-bar 1{r_brace} for the {alpha}-PbO{sub 2}-type TiO{sub 2} with varied extent of Cr dissolution. Surface modification, as a result of Cr dissolution and/or internal stress, was observed for all the polymorphs.

  5. A c. 1710 Ma mafic sill emplaced into a quartzite and calcareous series from Ighrem, Anti-Atlas - Morocco: Evidence that the Taghdout passive margin sedimentary group is nearly 1 Ga older than previously thought

    Science.gov (United States)

    Ikenne, Moha; Söderlund, Ulf; Ernst, Richard E.; Pin, Christian; Youbi, Nasrrddine; El Aouli, El Hassan; Hafid, Ahmid

    2017-03-01

    The Taghdout Group is a passive margin sequence deposited during rifting and break-up of the northern margin of the West African craton (WAC), culminating with the creation of an oceanic basin between the northern edge of the WAC and an unknown terrane. However, the age of this passive margin has been poorly constrained. It was previously thought to be c. 800-1000 Ma on the basis of age of the contact metamorphosed host rocks of the associated mafic dykes (Rb/Sr, 789 ± 10 Ma). However, with the U-Pb dating of numerous dyke swarms in the Anti-Atlas Inliers, at c. 870, 1416-1380, 1650, 1750, and 2040 Ma, it was suggested by Youbi et al. (2013) that the Taghdout Group could be Mesoproterozoic in age, with a preference for an age of 1750 Ma. In order to test this idea, a mafic sill within the Taghdout Group has been dated by the ID-TIMS U-Pb method on baddeleyite, yielding an approximate age of c. 1710 Ma. This preliminary age confirms that the Taghdout Group is much older than previously thought. Further geochronology work is required to determine whether this c. 1710 Ma age represents a new intraplate event in the WAC or whether more concordant data could yield an age closer to the known WAC LIP event of c. 1750 Ma. With this result we propose a new lithostratigraphic framework for the Proterorozoic in the Anti-Atlas.

  6. Crystalline phase, microstructure, and aqueous stability of zirconolite-barium borosilicate glass-ceramics for immobilization of simulated sulfate bearing high-level liquid waste

    Science.gov (United States)

    Wu, Lang; Xiao, Jizong; Wang, Xin; Teng, Yuancheng; Li, Yuxiang; Liao, Qilong

    2018-01-01

    The crystalline phase, microstructure, and aqueous stability of zirconolite-barium borosilicate glass-ceramics with different content (0-30 wt %) of simulated sulfate bearing high-level liquid waste (HLLW) were evaluated. The sulfate phase segregation in vitrification process was also investigated. The results show that the glass-ceramics with 0-20 wt% of HLLW possess mainly zirconolite phase along with a small amount baddeleyite phase. The amount of perovskite crystals increases while the amount of zirconolite crystals decreases when the HLLW content increases from 20 to 30 wt%. For the samples with 20-30 wt% HLLW, yellow phase was observed during the vitrification process and it disappeared after melting at 1150 °C for 2 h. The viscosity of the sample with 16 wt% HLLW (HLLW-16) is about 27 dPa·s at 1150 °C. The addition of a certain amount (≤20 wt %) of HLLW has no significant change on the aqueous stability of glass-ceramic waste forms. After 28 days, the 90 °C PCT-type normalized leaching rates of Na, B, Si, and La of the sample HLLW-16 are 7.23 × 10-3, 1.57 × 10-3, 8.06 × 10-4, and 1.23 × 10-4 g·m-2·d-1, respectively.

  7. Achaean TTG and high alimunia gneisses on Baltic Shield: Precise U-Pb (ID-TIMS) and SHRIMP-II ages on single zircon

    Science.gov (United States)

    Bayanova, Tamara; Morozova, Ludmila; Mitrofanov, Felix; Serov, Pavel; Nitkina, Elena; Fedotov, Dzorzh; Larionov, Alexander

    2014-05-01

    New U-Pb (ID-TIMS) data on single zircon from high alimunia gneisses near Murmansk in the Central-Kola domain gave 3.17 Ga. Core from these zircon population has the age 3695±5 Ma by SHRIMP-II. Time of amphibolites metamorphism was dated with 2753±3 Ma. Achaean gneisses in Monchegorsk ore region were firstly dated in the Central-Kola domain. Single zircon from gneisses in Monchegorsk region which are the basement for Paleoproterozoic PGE layered intrusions with U-Pb ages on zircon and baddeleyite from 2.4-to 2.5 Ga (Bayanova et all, 2009) has 3.16 Ga. Single zircon from gnneisses gave 2776±3 Ma and is considered as amphibolites metamorphism. Voche-Lambina international polygon lies on the boundary between Belomorian mobile block and Central -Kola domain (Morozova et al, 2011). New neoarhaean U-Pb data on single zircon from TTG of polygon yielded 3158.2±8.2. Zircon are characterized by low concentration U and Pb, low U/Th ratio with 0.2. REE diagrams of grey gneisses reflect high fractionation La/Yb>30,encriched by light REE and depleted by heavy Yb<0.6 ppm. Model Sm-Ng ages on the rocks have protolith from with the ages 3.4 to 3.2 Ga, positive ɛNd from +1.29 to +3.3, ISr equals 0.702. Precise (ID-TIMS) age of amphibolites metamorphism has been dated on single zircon with 2704.3±5.9 Ma. In the frame of the Central-Kola domain there is an Ingosersky TTG complex. Firstly U-Pb dating on single zircon from Bt-gneisses reflects 3149±49 Ma. Metamorphic alterations were in 2725.2±2.5 Ma and connected with origin of Amf-Bt gneisses and 2733.6±6.6 with Bt-Amf gneisses. (NItkina et al., 2012). Therefore based on the new data on single zircon from TTG and high alimunia gneisses from Central-Kola domain leads to the long history of continental crust origin in the Baltic or Fennoscandian Shield from 3.16 to 3.7 Ga. We thank to G. Wasserburg for 205 Pb artificial spike, J. Ludden for 91500 and Temora standards, F. Corfu, V. Todt and U. Poller for assistance in the

  8. Origin of carbonatites of the Matcha alkaline pluton from Turkestan-Alai ridge, Kyrgyz Southern Tien Shan

    Science.gov (United States)

    Vrublevskii, V. V.

    2017-12-01

    Postorogenic alkaline intrusions in the Turkestan-Alai segment of the Southern Tien Shan coexist with dikes and veins of carbonatites dated at ˜220 Ma. They are primarily composed of calcite and dolomite (60-85 %), as well as sodic amphibole, phlogopite, clinopyroxene, microcline, albite, apatite, and magnetite, with accessory niobate, ilmenite, Nb-rutile, titanite, zircon, baddeleyite, monazite-(Ce), barite, and sulfides. The rocks share mineralogical and geochemical similarity with carbonatites that originated by liquid immiscibility at high temperatures above 500°C. Silicate and salt-carbonate melts are derived from sources with mainly negative bulk ɛND(t) ˜ from -11 to 0 and high initial 87Sr/86Sr ratios (˜ 0.7061-0.7095) which may be due to mixing of PREMA and EM-type mantle material. Pb isotopic ratios in accessory pyrrhotite (206Pb/204Pb = 18.38; 207Pb/204Pb = 15.64; 208Pb/204Pb = 38.41) exhibit an EM 2 trend. The intrusions bear signatures of significant crustal contamination as a result of magma genesis by syntexis and hybridism. Concordant isotope composition changes of δ 13C (-6.5 to -1.9 ‰), δ 18O (9.2-23 %„), δD (-58 to -41 %„), and δ 34S (12.6-12.8 ‰) in minerals and rocks indicate inputs of crustal material at the stage of melting and effect of hot fluids released during dehydration of metamorphosed oceanic basalts or sediments. The observed HFSE patterns of the oldest alkaline gabbro may be due to interaction of the primary mafic magma with IAB-type material. The isotope similarity of alkaline rocks with spatially proximal basalts of the Tarim large igneous province does not contradict the evolution of the Turkestan-Alai Triassic magmatism as the «last echo» of the Tarim mantle plume.

  9. Extreme biomimetic approach for synthesis of nanocrystalline chitin-(Ti,Zr)O{sub 2} multiphase composites

    Energy Technology Data Exchange (ETDEWEB)

    Wysokowski, Marcin, E-mail: Marcin.Wysokowski@put.poznan.pl [Poznan University of Technology, Faculty of Chemical Technology, Institute of Chemical Technology and Engineering, Berdychowo 4, 60965, Poznan (Poland); Motylenko, Mykhaylo; Rafaja, David [TU Bergakademie Freiberg, Institute of Materials Science, Gustav-Zeuner-Str. 5, 09596, Freiberg (Germany); Koltsov, Iwona [Laboratory of Nanostructures, Institute of High Pressure Physics of The Polish Academy of Sciences, Sokołowska 29/37, 01-142, Warsaw (Poland); Stöcker, Hartmut [TU Bergakademie Freiberg, Institute of Experimental Physics, Leipziger str. 23, 09596, Freiberg (Germany); Szalaty, Tadeusz J. [Poznan University of Technology, Faculty of Chemical Technology, Institute of Chemical Technology and Engineering, Berdychowo 4, 60965, Poznan (Poland); Bazhenov, Vasilii V., E-mail: vasily.bazhenov@gmail.com [TU Bergakademie Freiberg, Institute of Experimental Physics, Leipziger str. 23, 09596, Freiberg (Germany); Stelling, Allison L. [Duke University, Department of Biochemistry, Durham, NC, 27708 (United States); Beyer, Jan; Heitmann, Johannes [TU Bergakademie Freiberg, Institute of Applied Physics, Leipziger str. 23, 09596, Freiberg (Germany); Jesionowski, Teofil [Poznan University of Technology, Faculty of Chemical Technology, Institute of Chemical Technology and Engineering, Berdychowo 4, 60965, Poznan (Poland); Petovic, Slavica; Đurović, Mirko [Institute of Marine Biology, Dobrota, 85330, Kotor (Montenegro); Ehrlich, Hermann [TU Bergakademie Freiberg, Institute of Experimental Physics, Leipziger str. 23, 09596, Freiberg (Germany)

    2017-02-15

    This work presents an extreme biomimetics route for the modification of the surface of fibre-based scaffolds of poriferan origin by the creation of novel nanostructured multiphase biocomposites. The exceptional thermal stability of the nanostructured sponge chitin allowed for the formation of a novel nanocrystalline chitin-(Ti,Zr)O{sub 2} composite with a well-defined nanoscale structure under hydrothermal conditions (160 °C). Using a combination of experimental techniques, including X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, EDX mapping and near-edge electron loss spectroscopy (ELNES) in TEM and thermogravimetry/differential scanning calorimetry coupled with mass spectrometry; we showed that this bioorganic scaffold facilitates selective crystallization of TiO{sub 2}, predominantly in form of anatase, over the monoclinic zirconium dioxide (baddeleyite). The control of the crystal morphology through the chitin templates is also demonstrated. Obtained samples were characterized in terms of their photoluminescent properties and photocatalytic performance. These data confirm the high potential of the extreme biomimetics approach for developing a new generation of multiphase biopolymer-based nanostructured materials. - Highlights: • Extreme biomimetically prepared chitin-(Ti,Zr)O{sub 2} and (Ti,Zr)O{sub 2} composites. • Chitin-(Ti,Zr)O{sub 2} composite contains anatase as the most inorganic component. • The mean crystallite size is (31.7 ± 0.3) nm for chitin-(Ti,Zr)O{sub 2} composite. • The mean crystallite size is (2.4 ± 0.5) nm for (Ti,Zr)O{sub 2} composite. • (Ti,Zr)O{sub 2} composite is 2 times more effective photocatalyst than chitin-(Ti,Zr)O{sub 2}.

  10. Magmatic (silicates/saline/sulfur-rich/CO2) immiscibility and zirconium and rare-earth element enrichment from alkaline magma chamber margins : Evidence from Ponza Island, Pontine Archipelago, Italy

    Science.gov (United States)

    Belkin, H.E.; de Vivo, B.; Lima, A.; Torok, K.

    1996-01-01

    Fluid inclusions were measured from a feldspathoid-bearing syenite xenolith entrained in trachyte from Ponza, one of the islands of the Pontine Archipelago, located in the Gulf of Gaeta, Italy. The feldspathoid-bearing syenite consists mainly of potassium feldspar, clinopyroxene, amphibole, biotite, titanite, manganoan magnetite, apatite with minor nosean, Na-rich feldspar, pyrrhotite, and rare cheralite. Baddeleyite and zirkelite occur associated with manganoan magnetite. Detailed electron-microprobe analysis reveals enrichments in REE, Y, Nb, U, Th as well as Cl and F in appropriate phases. Fluid inclusions observed in potassium feldspar are either silicate-melt or aqueous inclusions. The aqueous inclusions can be further classified as. (1) one-phase vapor, (2) two-phase (V + L) inclusions, vapor-rich inclusions with a small amount of CO2 in most cases; homogenization of the inclusions always occurred in the vapor phase between 359 and 424??C, salinities vary from 2.9 to 8.5 wt. % NaCl equivalent; and. (3) three-phase and multiphase inclusions (hypersaline/sulfur-rich aqueous inclusions sometimes with up to 8 or more solid phases). Daughter minerals dissolve on heating before vapor/liquid homogenization. Standardless quantitative scanning electron microscope X-ray fluorescence analysis has tentatively identified the following chloride and sulfate daughter crystals; halite, sylvite, glauberite. arcanite, anhydrite, and thenardite. Melting of the daughter crystals occurs between 459 and 536??C (54 to 65 wt. % NaCI equivalent) whereas total homogenization is between 640 and 755??C. The occurrence of silicate-melt inclusions and high-temperature, solute-rich aqueous inclusions suggests that the druse or miarolitic texture of the xenolith is late-stage magmatic. The xenolith from Ponza represents a portion of the peripheral magma chamber wall that has recorded the magmatic/hydrothermal transition and the passage of high solute fluids enriched in chlorides, sulfur, and

  11. δ18O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material

    Science.gov (United States)

    Longinelli, Antonio; Sighinolfi, Giampaolo; de Michele, Vincenzo; Selmo, Enricomaria

    2011-02-01

    Oxygen isotope and chemical measurements were carried out on 25 samples of Libyan Desert Glass (LDG), 21 samples of sandstone, and 3 of sand from the same area. The δ18O of LDG samples range from 9.0‰ to 11.9‰ (Vienna Standard Mean Ocean Water [VSMOW]); some correlations between isotope data and typological features of the LDG samples are pointed out. The initial δ18O of a bulk parent material may be slightly increased by fusion due to the loss of isotopically light pore water with no isotope exchange with oxygen containing minerals. Accordingly, the δ18O of the bulk parent material of LDG may have been about 9.0 ± 1‰ (VSMOW). The measured bulk sandstone and sand samples have δ18O values ranging from 12.6‰ to 19.5‰ and are consequently ruled out as parent materials, matching the results of previous studies. However, separated quartz fractions have δ18O values compatible with the LDG values suggesting that the modern surface sand inherited quartz from the target material. This hypothesis fits previous findings of lechatelierite and baddeleyite in these materials. As the age of the parent material reported in previous studies is Pan-African, we measured the δ18O values of bulk rock and quartz from intrusives of Pan-African age and the results obtained were compatible with the LDG values. The main element abundances (Fe, Mg, Ca, K, Na) in our LDG samples conform to previous estimates; Fe, Mg, and K tend to be higher in heterogeneous samples with dark layers. The hypothesis of a low-altitude airburst involving silica-rich surface materials deriving from weathered intrusives of Pan-African age, partially melted and blown over a huge surface by supersonic winds matches the results obtained.

  12. The P3 kimberlite and P4 lamproite, Wajrakarur kimberlite field, India: mineralogy, and major and minor element compositions of olivines as records of their phenocrystic vs xenocrystic origin

    Science.gov (United States)

    Shaikh, Azhar M.; Kumar, Satya P.; Patel, Suresh C.; Thakur, Satyajeet S.; Ravi, Subramanian; Behera, Duryadhan

    2018-03-01

    Distinctly different groundmass mineralogy characterise the hypabyssal facies, Mesoproterozoic diamondiferous P3 and P4 intrusions from the Wajrakarur Kimberlite Field, southern India. P3 is an archetypal kimberlite with macrocrysts of olivine and phlogopite set in a groundmass dominated by phlogopite and monticellite with subordinate amounts of serpentine, spinel, perovskite, apatite, calcite and rare baddeleyite. P4 contains mega- and macrocrysts of olivine set in a groundmass dominated by clinopyroxene and phlogopite with subordinate amounts of serpentine, spinel, perovskite, apatite, and occasional gittinsite, and is mineralogically interpreted as an olivine lamproite. Three distinct populations of olivine, phlogopite and clinopyroxene are recognized based on their microtextural and compositional characteristics. The first population includes glimmerite and phlogopite-clinopyroxene nodules, and Mg-rich olivine macrocrysts (Fo 90-93) which are interpreted to be derived from disaggregated mantle xenoliths. The second population comprises macrocrysts of phlogopite and Fe-rich olivine (Fo 81-89) from P3, megacrysts and macrocrysts of Fe-rich olivine (Fo 85-87) from P4 and a rare olivine-clinopyroxene nodule from P4 which are suggested to have a genetic link with the precursor melt of the respective intrusions. The third population represents clearly magmatic minerals such as euhedral phenocrysts of Fe-rich olivine (Fo 85-90) crystallised at mantle depths, and olivine overgrowth rims formed contemporaneously with groundmass minerals at crustal levels. Close spatial association and contemporaneous emplacement of P3 kimberlite and P4 lamproite is explained by a unifying petrogenetic model which involves the interaction of a silica-poor carbonatite melt with differently metasomatised wall rocks in the lithospheric mantle. It is proposed that the metasomatised wall rock for lamproite contained abundant MARID-type and phlogopite-rich metasomatic veins, while that for

  13. Magmatic-hydrothermal fluid interaction and mineralization in alkali-syenite nodules from the Breccia Museo pyroclastic deposit, Naples, Italy: Chapter 7 in Volcanism in the Campania Plain — Vesuvius, Campi Flegrei and Ignimbrites

    Science.gov (United States)

    Fedele, Luca; Tarzia, Maurizio; Belkin, Harvey E.; De Vivo, Benedetto; Lima, Annamaria; Lowenstern, Jacob

    2007-01-01

    The Breccia Museo, a pyroclastic flow that crops out in the Campi Flegrei volcanic complex (Naples, Italy), contains alkali-syenite (trachyte) nodules with enrichment in Cl and incompatible elements (e.g., U, Zr, Th, and rare-earth elements). Zircon was dated at ≈52 ka, by U-Th isotope systematics using a SHRIMP. Scanning electron microscope and electron microprobe analysis of the constituent phases have documented the mineralogical and textural evolution of the nodules of feldspar and mafic accumulations on the magma chamber margins. Detailed electron microprobe data are given for alkali and plagioclase feldspar, salite to ferrosalite clinopyroxene, pargasite, ferrogargasite, magnesio-hastingsite hornblende amphibole, biotite mica, Cl-rich scapolite, and a member (probable davyne-type) of the cancrinite group. Detailed whole rock, major and minor element data are also presented for selected nodules. A wide variety of common and uncommon accessory minerals were identified such as zircon, baddeleyite, zirconolite, pollucite, sodalite, titanite, monazite, cheralite, apatite, titanomagnetite and its alteration products, scheelite, ferberite, uraninite/thorianite, uranpyrochlore, thorite, pyrite, chalcopyrite, and galena. Scanning electron microscope analysis of opened fluid inclusions identified halite, sylvite, anhydrite, tungstates, carbonates, silicates, sulfides, and phosphates; most are probably daughter minerals. Microthermometric determinations on secondary fluid inclusions hosted by alkali feldspar define a temperature regime dominated by hypersaline aqueous fluids. Fluid-inclusion temperature data and mineral-pair geothermometers for coexisting feldspars and hornblende and plagioclase were used to construct a pressure-temperature scenario for the development and evolution of the nodules. We have compared the environment of porphyry copper formation and the petrogenetic environment constructed for the studied nodules. The suite of ore minerals observed in

  14. Extreme biomimetic approach for synthesis of nanocrystalline chitin-(Ti,Zr)O2 multiphase composites

    International Nuclear Information System (INIS)

    Wysokowski, Marcin; Motylenko, Mykhaylo; Rafaja, David; Koltsov, Iwona; Stöcker, Hartmut; Szalaty, Tadeusz J.; Bazhenov, Vasilii V.; Stelling, Allison L.; Beyer, Jan; Heitmann, Johannes; Jesionowski, Teofil; Petovic, Slavica; Đurović, Mirko; Ehrlich, Hermann

    2017-01-01

    This work presents an extreme biomimetics route for the modification of the surface of fibre-based scaffolds of poriferan origin by the creation of novel nanostructured multiphase biocomposites. The exceptional thermal stability of the nanostructured sponge chitin allowed for the formation of a novel nanocrystalline chitin-(Ti,Zr)O 2 composite with a well-defined nanoscale structure under hydrothermal conditions (160 °C). Using a combination of experimental techniques, including X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, EDX mapping and near-edge electron loss spectroscopy (ELNES) in TEM and thermogravimetry/differential scanning calorimetry coupled with mass spectrometry; we showed that this bioorganic scaffold facilitates selective crystallization of TiO 2 , predominantly in form of anatase, over the monoclinic zirconium dioxide (baddeleyite). The control of the crystal morphology through the chitin templates is also demonstrated. Obtained samples were characterized in terms of their photoluminescent properties and photocatalytic performance. These data confirm the high potential of the extreme biomimetics approach for developing a new generation of multiphase biopolymer-based nanostructured materials. - Highlights: • Extreme biomimetically prepared chitin-(Ti,Zr)O 2 and (Ti,Zr)O 2 composites. • Chitin-(Ti,Zr)O 2 composite contains anatase as the most inorganic component. • The mean crystallite size is (31.7 ± 0.3) nm for chitin-(Ti,Zr)O 2 composite. • The mean crystallite size is (2.4 ± 0.5) nm for (Ti,Zr)O 2 composite. • (Ti,Zr)O 2 composite is 2 times more effective photocatalyst than chitin-(Ti,Zr)O 2 .

  15. Radioactivity and associated radiation hazards in ceramic raw materials and end products.

    Science.gov (United States)

    Viruthagiri, G; Rajamannan, B; Suresh Jawahar, K

    2013-12-01

    Studies have been planned to obtain activity and associated radiation hazards in ceramic raw materials (quartz, feldspar, clay, zircon, kaolin, grog, alumina bauxite, baddeleyite, masse, dolomite and red mud) and end products (ceramic brick, glazed ceramic wall and floor tiles) as the activity concentrations of uranium, thorium and potassium vary from material to material. The primordial radionuclides in ceramic raw materials and end products are one of the sources of radiation hazard in dwellings made of these materials. By the determination of the activity level in these materials, the indoor radiological hazard to human health can be assessed. This is an important precautionary measure whenever the dose rate is found to be above the recommended limits. The aim of this work was to measure the activity concentration of (226)Ra, (232)Th and (40)K in ceramic raw materials and end products. The activity of these materials has been measured using a gamma-ray spectrometry, which contains an NaI(Tl) detector connected to multichannel analyser (MCA). Radium equivalent activity, alpha-gamma indices and radiation hazard indices associated with the natural radionuclides are calculated to assess the radiological aspects of the use of the ceramic end products as decorative or covering materials in construction sector. Results obtained were examined in the light of the relevant international legislation and guidance and compared with the results of similar studies reported in different countries. The results suggest that the use of ceramic end product samples examined in the construction of dwellings, workplace and industrial buildings is unlikely to give rise to any significant radiation exposure to the occupants.

  16. Zirconium - an imported mineral commodity

    International Nuclear Information System (INIS)

    1983-10-01

    This report examines Canada's position in regard to the principal zirconium materials: zircon; fusion-cast zirconium-bearing refractory products; zirconium-bearing chemicals; and zirconium metal, master alloys, and alloys. None of these is produced in Canada except fused alumina-zirconia and certain magnesium-zirconium alloys and zirconium-bearing steels. Most of the 3 000-4 000 tonnes of the various forms of zircon believed to be consumed in Canada each year is for foundry applications. Other minerals, notably chromite, olivine and silica sand are also used for these purposes and, if necessary, could be substituted for zircon. Zirconium's key role in Canada is in CANDU nuclear power reactors, where zirconium alloys are essential in the cladding for fuel bundles and in capital equipment such as pressure tubes, calandria tubes and reactivity control mechanisms. If zirconium alloys were to become unavailable, the Canadian nuclear power industry would collapse. As a contingency measure, Ontario Hydro maintains at least nine months' stocks of nuclear fuel bundles. Canada's vulnerability to short-term disruptions to supplies of nuclear fuel is diminished further by the availability of more expensive electricity from non-nuclear sources and, given time, from mothballed thermal plants. Zirconium minerals are present in many countries, notably Australia, the Republic of South Africa and the United States. Australia is Canada's principal source of zircon imports; South Africa is its sole source of baddeleyite. At this time, there are no shortages of either material. Canada has untapped zirconium resources in the Athabasca Oil Sands (zircon) and at Strange Lake along the ill-defined border between Quebec and Newfoundland (gittinsite). Adequate metal and alloy production facilities exist in France, Japan and the United States. No action by the federal government in regard to zirconium supplies is called for at this time

  17. Radioactivity and associated radiation hazards in ceramic raw materials and end products

    International Nuclear Information System (INIS)

    Viruthagiri, G.; Rajamannan, B.; Suresh Jawahar, K.

    2013-01-01

    Studies have been planned to obtain activity and associated radiation hazards in ceramic raw materials (quartz, feldspar, clay, zircon, kaolin, grog, alumina bauxite, baddeleyite, masse, dolomite and red mud) and end products (ceramic brick, glazed ceramic wall and floor tiles) as the activity concentrations of uranium, thorium and potassium vary from material to material. The primordial radionuclides in ceramic raw materials and end products are one of the sources of radiation hazard in dwellings made of these materials. By the determination of the activity level in these materials, the indoor radiological hazard to human health can be assessed. This is an important precautionary measure whenever the dose rate is found to be above the recommended limits. The aim of this work was to measure the activity concentration of 226 Ra, 232 Th and 40 K in ceramic raw materials and end products. The activity of these materials has been measured using a gamma-ray spectrometry, which contains an NaI(Tl) detector connected to multichannel analyser (MCA). Radium equivalent activity, alpha-gamma indices and radiation hazard indices associated with the natural radionuclides are calculated to assess the radiological aspects of the use of the ceramic end products as decorative or covering materials in construction sector. Results obtained were examined in the light of the relevant international legislation and guidance and compared with the results of similar studies reported in different countries. The results suggest that the use of ceramic end product samples examined in the construction of dwellings, workplace and industrial buildings is unlikely to give rise to any significant radiation exposure to the occupants. (authors)

  18. Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia)

    Science.gov (United States)

    Yakovenchuk, Victor N.; Ivanyuk, Gregory Yu.; Pakhomovsky, Yakov A.; Panikorovskii, Taras L.; Britvin, Sergei N.; Krivovichev, Sergey V.; Shilovskikh, Vladimir V.; Bocharov, Vladimir N.

    2018-02-01

    Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma, a = 11.256(1), b = 8.512(1), c = 27.707(4) Å, V = 2654.6(3) Å3 and Z = 4 (from powder diffraction data) or a = 11.2261(9), b = 8.5039(6), c = 27.699(2) Å, V = 2644.3(3) Å3 (from single-crystal diffraction data). The mineral was found in a void within the calcite-magnetite phoscorite (enriched in hydroxylapatite and Sc-rich baddeleyite) inside the axial zone of the Kovdor phoscorite-carbonatite pipe. Kampelite forms radiated aggregates (up to 1.5 mm in diameter) of platy crystals grown on the surfaces of crystals of quintinite-2 H in close association with pyrite, bobierrite and quintinite-3 R. Kampelite is colourless, with a pearly lustre and a white streak. The cleavage is perfect on {001}, the fracture is smooth. Mohs hardness is about 1. In transmitted light, the mineral is colourless without pleochroism or dispersion. Kampelite is biaxial + (pseudouniaxial), α ≈ β = 1.607(2), γ = 1.612(2) (589 nm), and 2 V calc = 0°. The calculated and measured densities are 3.28 and 3.07(3) g·cm-3, respectively. The mean chemical composition determined by electron microprobe is: MgO 4.79, Al2O3 0.45, P2O5 31.66, K2O 0.34, Sc2O3 16.17, Mn2O3 1.62, Fe2O3 1.38, SrO 3.44, and BaO 29.81 wt%. The H2O content estimated from the crystal-structure refinement is 7.12 wt%, giving a total of 96.51 wt%. The empirical formula calculated on the basis of P = 6 apfu (atoms per formula unit) is (Ba2.62Sr0.45K0.10Ca0.06)Σ3.23Mg1.60Mn0.28(Sc3.15Fe3+ 0.23Al0.12)Σ3.50(PO4)6(OH)2.61·4.01H2O. The simplified formula is Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O. The mineral easily dissolves in 10% cold HCl. The strongest X-ray powder-diffraction lines [listed as d in Å ( I) ( hkl)] are as follows: 15.80(100)(001), 13.86(45)(002), 3.184(18)(223), 3.129(19)(026), 2.756(16)(402), 2.688(24)(10 10). The crystal structure of kampelite was

  19. The Halti-Corrovarre enigma in the northern Scandes: new ID-TIMS U/Pb zircon data

    Science.gov (United States)

    Andréasson, Per-Gunnar; Corfu, Fernando; Gee, David G.

    2013-04-01

    The Caledonides of northern Norway are dominated by the Kalak Nappe Complex (KNC), mainly composed of greenschist facies quartzo-feldspathic sandstones, variously intruded by dolerite dykes and minor granites. The highest components of the KNC, the Halti, Corrovarre, Seiland and Gjesvaer nappes (apparently the same structural level), are of higher metamorphic grade and include prominent igneous suites. The Halti and Corrovarre nappes comprise mafic dyke-swarms that intrude and partially melt the meta-sandstones and also include both ultramafites and gabbros. By contrast, the Seiland nappe is dominated by a major igneous province ranging in composition from alkaline gabbro to nepheline syenite and the Gjesvaer nappe is dominated by migmatites. The KNC overrides other thrust sheets, also dominated by siliciclastic successions, the Laksefjord and Gaissa nappes, and all these allochthons overlie a thin Cambrian-Ediacaran sedimentary veneer and the Precambrian crystalline basement of Baltica. Palinspastic reconstructions of the nappes indicate that the KNC has been emplaced at least two hundred kilometres southeastwards onto the Baltoscandian platform; attempts to balance cross-sections have suggested transport distance of the highest Kalak nappes to be in the order of three times this distance. Mapping of the Kalak nappes southwards into Sweden has established their correlation with the Särv and Seve nappes, together comprising the Middle Allochthon. Recent ID-TIMS, U/Pb dating by one of us (FC) of zircons extracted from granitic melts within the dyke-swarms of the Halti and Corrovarre nappes has confirmed the results of previous studies. In Halti, ages of 441-436 Ma compare well with previous zircon and baddeleyite studies; this dunite, troctolite, gabbro, sheeted-dyke suite is of early Llandovery age, overlapping in time with the early Scandian collision of Baltica and Laurentia. In Corrovarre, the granitic melts within the dyke-swarm yield 610 Ma ages, closely

  20. Extreme isotopologue disequilibrium in molecular SIMS species during SHRIMP geochronology

    Science.gov (United States)

    Magee, Charles W., Jr.; Danišík, Martin; Mernagh, Terry

    2017-12-01

    The current limitation in the accuracy and precision of inter-element analysis in secondary ion mass spectrometry (SIMS) is the ability to find measurable quantities that allow relative differences in ionization and transmission efficiency of secondary ions to be normalized. In uranium-thorium-lead geochronology, the ability to make these corrections, or "calibrate" the data, results in an accuracy limit of approximately 1 %. This study looks at the ionization of uranium and thorium oxide species, which are traditionally used in U-Pb calibration, to explore the conditions under which isotopologues, or molecular species whose composition differs only in the isotopic composition of one or more atoms in the molecule, remain in or deviate from equilibrium. Isotopologue deficits of up to 0.2 (200 ‰) below ideal mixing are observed in UO2+ species during SIMS gechronological analyses using the SHRIMP IIe SIMS instrument. These are identified by bombarding natural U-bearing minerals with an 18O2- primary beam. The large anomalies are associated with repeat analyses down a single SIMS sputtering crater (Compston et al., 1984), analysis of high-uranium, radiation-damaged zircon, and analysis of baddeleyite. Analysis of zircon under routine conditions yield UO2+ isotopologue anomalies generally within a few percent of equilibrium. The conditions under which the isotopologue anomalies are observed are also conditions in which the UOx-based corrections, or calibration, for relative U vs. Pb ionization efficiencies fail. The existence of these isotopologue anomalies suggest that failure of the various UOx species to equilibrate with each other is the reason that none of them will successfully correct the U  / Pb ratio. No simple isotopologue-based correction is apparent. However, isotopologue disequilibrium appears to be a more sensitive tool for detecting high-U calibration breakdowns than Raman spectroscopy, which showed sharper peaks for ˜ 37 Ma high-uranium zircons

  1. Coordinated U-Pb geochronology, trace element, Ti-in-zircon thermometry and microstructural analysis of Apollo zircons

    Science.gov (United States)

    Crow, Carolyn A.; McKeegan, Kevin D.; Moser, Desmond E.

    2017-04-01

    We present the results of a coordinated SIMS U-Pb, trace element, Ti-in-zircon thermometry, and microstructural study of 155 lunar zircons separated from Apollo 14, 15, and 17 breccia and soil samples that help resolve discrepancies between the zircon data, the lunar whole rock history and lunar magma ocean crystallization models. The majority of lunar grains are detrital fragments, some nearly 1 mm in length, of large parent crystals suggesting that they crystallized in highly enriched KREEP magmas. The zircon age distributions for all three landing sites exhibit an abundance of ages at ∼4.33 Ga, however they differ in that only Apollo 14 samples have a population of zircons with ages between 4.1 and 3.9 Ga. These younger grains comprise only 10% of all dated lunar zircons and are usually small and highly shocked making them more susceptible to Pb-loss. These observations suggest that the majority of zircons crystallized before 4.1 Ga and that KREEP magmatism had predominantly ceased by this time. We also observed that trace element analyses are easily affected by contributions from inclusions (typically injected impact melt) within SIMS analyses spots. After filtering for these effects, rare-earth element (REE) abundances of pristine zircon are consistent with one pattern characterized by a negative Eu anomaly and no positive Ce anomaly, implying that the zircons formed in a reducing environment. This inference is consistent with crystallization temperatures based on measured Ti concentrations and new estimates of oxide activities which imply temperatures ranging between 958 ± 57 and 1321 ± 100 °C, suggesting that zircon parent magmas were anhydrous. Together, the lunar zircon ages and trace elements are consistent with a ⩽300 My duration of KREEP magmatism under anhydrous, reducing conditions. We also report two granular texture zircons that contain baddeleyite cores, which both yield 207Pb-206Pb ages of 4.33 Ga. These grains are our best constraints on

  2. Mineralogy and geochemistry of triassic carbonatites in the Matcha alkaline intrusive complex (Turkestan-Alai Ridge, Kyrgyz Southern Tien Shan), SW Central Asian orogenic belt

    Science.gov (United States)

    Vrublevskii, V. V.; Morova, A. A.; Bukharova, O. V.; Konovalenko, S. I.

    2018-03-01

    Postorogenic intrusions of essexites and alkaline and nepheline syenites in the Turkestan-Alai segment of the Kyrgyz Southern Tien Shan coexist with dikes and veins of carbonatites dated at ∼220 Ma by the Ar-Ar and Rb-Sr age methods. They are mainly composed of calcite and dolomite (60-85%), as well as sodic amphibole, phlogopite, clinopyroxene, microcline, albite, apatite, and magnetite, with accessory niobate, ilmenite, Nb-rutile, titanite, zircon, baddeleyite, monazite-(Ce), barite, and sulfides. The rocks share mineralogical and geochemical similarity with carbonatites that originated by liquid immiscibility at high temperatures above 500 °C. Alkaline silicate and salt-carbonate melts are derived from sources with mainly negative bulk εNd(t) ∼ from -11 to 0 and high initial 87Sr/86Sr ratios (∼0.7061-0.7095) which may be due to mixing of PREMA and EM-type mantle material. Pb isotopic ratios in accessory pyrrhotite (206Pb/204Pb = 18.38; 207Pb/204Pb = 15.64; 208Pb/204Pb = 38.41) exhibit an EM2 trend. The intrusions bear signatures of significant crustal contamination as a result of magma genesis by syntexis and hybridism. Concordant isotope composition changes of δ13C (-6.5 to -1.9‰), δ18O (9.2-23‰), δD (-58 to -41‰), and δ34S (12.6-12.8‰) in minerals and rocks indicate inputs of crustal material at the stage of melting and effect of hot fluids released during dehydration of metamorphosed oceanic basalts or sediments. The observed HFSE patterns of the oldest alkaline gabbro may be due to interaction of the primary mafic magma with IAB-type material. The isotope similarity of alkaline rocks with spatially proximal basalts of the Tarim large igneous province does not contradict the evolution of the Turkestan-Alai Triassic magmatism as the "last echo" of the Tarim mantle plume.

  3. Multiphase inclusions in plagioclase from anorthosites in the Stillwater Complex, Montana: implications for the origin of the anorthosites

    Science.gov (United States)

    Loferski, P.J.; Arculus, R.J.

    1993-01-01

    Multiphase inclusions, consisting of clinopyroxene+ilmenite+apatite, occur within cumulus plagioclase grains from anorthosites in the Stillwater Complex, Montana, and in other rocks from the Middle Banded series of the intrusion. The textures and constant modal mineralogy of the inclusions indicate that they were incorporated in the plagioclase as liquid droplets that later crystallized rather than as solid aggregates. Their unusual assemblage, including a distinctive manganiferous ilmenite and the presence of baddeleyite (ZrO2), indicates formation from an unusual liquid. A process involving silicater liquid immiscibility is proposed, whereby small globules of a liquid enriched in Mg, Fe, Ca, Ti, P, REE, Zr and Mn exsolved from the main liquid that gave rise to the anorthosites, became trapped in the plagioclase, and later crystallized to form the inclusions. The immiscibility could have occurred locally within compositional boundaries around crystallizing plagioclase grains or it could have occurred pervasively throughout the liquid. It is proposed that the two immiscible liquids were analogous, n terms of their melt structures, to immiscible liquid pairs reported in the literature both in experiments and in natural basalts. For the previously reported pairs, immiscibility is between a highly polymerized liquid, typically granitic in composition, and a depolymerized liquid, typically ferrobasaltic in composition. In the case of the anorthosites, the depolymerized liquid is represented by the inclusions, and the other liquid was a highly polymerized aluminosilicate melt with a high normative plagioclase content from which the bulk of the anorthosites crystallized. Crystallization of the anorthosites from this highly polymerized liquid accounts for various distinctive textural and chemical features of the anorthosites compared to other rocks in the Stillwater Complex. A lack of correlation between P contents and chondrite-normalized rare earth element (REE) ratios

  4. Protoliths of enigmatic Archaean gneisses established from zircon inclusion studies: Case study of the Caozhuang quartzite, E. Hebei, China

    Directory of Open Access Journals (Sweden)

    Allen P. Nutman

    2014-07-01

    Full Text Available A diverse suite of Archaean gneisses at Huangbaiyu village in the North China Craton, includes rare fuchsite-bearing (Cr-muscovite siliceous rocks – known as the Caozhuang quartzite. The Caozhuang quartzite is strongly deformed and locally mylonitic, with silica penetration and pegmatite veining common. It contains abundant 3880–3600 Ma and some Palaeoarchaean zircons. Because of its siliceous nature, the presence of fuchsite and its complex zircon age distribution, it has until now been accepted as a (mature quartzite. However, the Caozhuang quartzite sample studied here is feldspathic. The shape and cathodoluminescence petrography of the Caozhuang quartzite zircons show they resemble those found in immature detrital sedimentary rocks of local provenance or in Eoarchaean polyphase orthogneisses, and not those in mature quartzites. The Caozhuang quartzite intra-zircon mineral inclusions are dominated by quartz, with lesser biotite, apatite (7% and alkali-feldspar, and most inclusions are morphologically simple. A Neoarchaean orthogneiss from near Huangbaiyu displays morphologically simple inclusions with much more apatite (73%, as is typical for fresh calc-alkaline granitoids elsewhere. Zircons were also examined from a mature conglomerate quartzite clast and an immature feldspathic sandstone of the overlying weakly metamorphosed Mesoproterozoic Changcheng System. These zircons have oscillatory zoning, showing they were sourced from igneous rocks. The quartzite clast zircons contain only rare apatite inclusions (<1%, with domains with apatite habit now occupied by intergrowths of muscovite + quartz ± Fe-oxides ± baddeleyite. We interpret that these were once voids after apatite inclusions that had dissolved during Mesoproterozoic weathering, which were then filled with clays ± silica and then weakly metamorphosed. Zircons in the immature feldspathic sandstone show a greater amount of preserved apatite (11%, but with petrographic

  5. High-pressure phase behaviors of ZnTiO3: ilmenite-perovskite transition, decomposition of perovskite into constituent oxides, and perovskite-lithium niobate transition

    Science.gov (United States)

    Akaogi, M.; Abe, K.; Yusa, H.; Kojitani, H.; Mori, D.; Inaguma, Y.

    2015-06-01

    High-pressure high-temperature phase transitions of ZnTiO3 ilmenite were examined using multianvil apparatus up to 25.5 GPa and 1,500 °C and diamond anvil cell to 26.5 GPa and about 2,000 °C. Combined results of the multianvil quench experiments and in situ diamond anvil cell experiments indicated that at about 10 GPa and 1,200 °C ZnTiO3 ilmenite transforms to orthorhombic perovskite which is converted to lithium niobate phase on release of pressure. The boundary of the ilmenite-provskite transition is expressed by P(GPa) = 15.9 - 0.005 T (°C). The high-pressure experiments also indicated that at 20-24 GPa and 1,000-1,400 °C ZnTiO3 orthorhombic perovskite dissociates into rocksalt-type ZnO + baddeleyite-type TiO2 which are recovered, respectively, as wurtzite-type ZnO and α-PbO2-type TiO2 at 1 atm. The boundary of the perovskite dissociation is expressed by P(GPa) = 8.7 + 0.011 T (°C). Molar volume changes of ZnTiO3 at ambient conditions were estimated as -4.7 % for the ilmenite-perovskite transition and -3.5 % for the perovskite decomposition into the oxides. The absence of CaIrO3-type postperovskite in ZnTiO3 is consistent with that dissociation of ZnTiO3 perovskite into the oxides has the larger molar volume change than -1 to -2 % of the perovskite-postperovskite transition in various ABO3 compounds and with previous data that ABO3 perovskites with relatively ionic B-O bonds do not transform to the postperovskite. The transition behaviors of ZnTiO3 are similar to those of MnTiO3 and FeTiO3, but ZnTiO3 perovskite dissociates into the constituent oxides.

  6. Preserved Flora and Organics in Impact Melt Breccias: Implications for Capturing Past Life on Mars

    Science.gov (United States)

    Schultz, P. H.; Harris, R. S.; Clemett, S.; Thomas-Keprta, K.

    2013-12-01

    At least seven impact glass-bearing deposits have been documented in the Argentine stratigraphy, each recording separate events between the Holocene and late Miocene [1,2]. Detailed evidence for their origin by impact includes: planar deformation features (PDFs in quartz, feldspars, pyroxene, olivine, etc.), asymmetric isotropization (i.e., alternate-twin deformation) in plagioclase, diaplectic phases, ultra-high temperature melting (e.g., lechatelierite, molten rutile) and decomposition (e.g., baddeleyite), and quench textures around minerals, e.g., beta-crystobalite, etc. [1-3]. Incorporation of materials from depth indicates that this was not an airburst but a series of crater-forming impacts. Many hand samples also contain relicts of extant biota. Scanning electron microprobe (SEM) images reveal preservation of delicate forms including: striated layers between vesicular impact glass and parallel vein-like features at higher magnification. The striated patterns resemble vascular bundles of the mesophyll (ground tissue) of a plant. Identifiable parts of the plant anatomy, e.g. papillae and cell walls, contain skeletal magnetite crystals and high-temperature, i.e., phases indicating that vitreous fossilization occurred at extremely high temperatures and rapid quench rates. The morphology is generally similar to contemporary regional grasses (pampas grass) including small spherules (papilla). The intricate forms (20nm to 20mm) indicate features rapidly preserved rather than simple impressions. Reaction zones (vesiculation and quenched minerals) along the interface between the melt and entrained plants indicate rapid quenching. Compositional mapping reveals the presence of insignificant levels of carbon, but chemical analyses confirm the high silica content (> 60%). Various analytical techniques (micro-Raman, TEM/SEM, and μltra-L2MS) further reveal the preserved organic materials, including tetracyclic pyrrolines, essential members of the group of porphyrin species

  7. Understanding Magmatic Timescales and Magma Dynamics in Proterozoic Anorthosites: a Geochronological Investigation of the Kunene Complex (Angola)

    Science.gov (United States)

    Brower, A. M.; Corfu, F.; Bybee, G. M.; Lehmann, J.; Owen-Smith, T.

    2016-12-01

    The Kunene Anorthosite Complex, located in south west Angola, is one of the largest massif-type anorthosite intrusions on Earth, with an areal extent of at least 18 000 km2. Previous studies considered the Complex to consist of a series of coalesced plutons. However, the ages and relative emplacement sequence of these plutons are unknown. Understanding the relative timing of the pluton emplacement is crucial for understanding how these enigmatic magmas form and how they rise through the crust. Here we present new high precision U-Pb ID-TIMS ages (n=10) on zircons and baddeleyites for many of the coalesced plutons across the 300-km-long anorthositic complex. These new geochronological results reveal subtle variations in crystallization age between the coalesced plutons. There is no gradual age progression between plutons, but distinct groupings of ages (Fig.1). Age clusters of 1379.8 ± 2 Ma (n=5) occur north of the Red Granite NE-SW-striking intrusions, whereas in the south there is an older age grouping of 1390.4 ± 2.3 (n=3). Two additional ages of 1400.5 ± 1.3 in the centre and 1438.4 ± 1.1 Ma in the south east have been obtained. These results indicate that the Kunene anorthosites were emplaced over 60 Ma and may suggest long-lived magmatic systems and/or slowly ascending plutons. We also find a link between pluton composition and age. In general, leuconoritic domains are older than the leucotroctolitic domains. This may imply that the first pulses of magma received a greater degree of contamination, forcing the broadly basaltic magma to produce orthopyroxene as the main mafic phase. The later pulses receive less contamination as they ascend through the already partially melted crust, producing olivine as the mafic phase and deforming the older domains. This study reiterates the multiphase petrogenesis of Proterozoic anorthosites and sheds light on the assembly of crystal-rich magmas as they ascend through the crust.

  8. Compositional variations of zirconolite from the Evate apatite deposit (Mozambique) as an indicator of magmatic-hydrothermal conditions during post-orogenic collapse of Gondwana

    Science.gov (United States)

    Hurai, Vratislav; Huraiová, Monika; Gajdošová, Michaela; Konečný, Patrik; Slobodník, Marek; Siegfried, Pete R.

    2017-11-01

    Zirconolite is documented from the Evate apatite-magnetite-carbonate deposit in the circular Monapo Klippe (eastern Mozambique)—a relic of Neoproterozoic nappe thrusted over the Mesoproterozoic basement of the Nampula block. Zirconolite enriched in rare earth elements—REE = Y + Lu+ΣLa-Yb (up to 24.11 wt% REE2O3, 0.596 apfu REE) creates thin rims around spinel and magnetite grains, whereas zirconolite enriched in U and Th (up to 18.88 wt% ThO2 + UO2, 0.293 apfu Th + U) replace the Late Ediacaran ( 590 Ma) zircon and baddeleyite along contacts with pyrrhotite and magnetite. Both types of zirconolite contain locally increased Nb and Ta concentrations (up to 7.58 wt% Nb2O5 + Ta2O5, 0.202 apfu Nb + Ta). Typical substitutions in zirconolite from Evate involve REE + U,Th → Ca, and M 2++M 5+→Ti + M 3+ (M 2+ = Fe2++Mg, M 3+ = Fe3+, M 5+ = Nb5++Ta5+). In addition, REE-zirconolite is typical of the REE + M 2+ → Ca + M 3+ substitution (M 2+ = Mg, M 3+ = Fe3++Al3+). Hence, Fe3+ predominates over Fe2+ in all types of zirconolite, thus enabling the high REE content in Nb-poor zirconolites to be stored in locally dominant REEZrTiFe3+O7 component known so far only as a synthetic analogue of natural zirconolite. Other types of zirconolite from Evate are dominated by the common CaZrTi2O7 end member, but the aforementioned "synthetic" REEZrTiFe3+O7 accompanied by another `synthetic' (U,Th)ZrFe3 + 2O7 component are also abundant. The U,Pb,Th concentrations in U,Th-zirconolites plot discordantly to theoretical isochrons, thus indicating 440 ppm of non-radiogenic excess lead in earlier Nb-rich zirconolite contrasting with secondary Pb loss from later Nb-poor zirconolite. The non-radiogenic Pb-corrected age of the early zirconolite corresponded to 485 ± 9 Ma, within uncertainty limit identical with the 493 ± 10 Ma age of the associated uranothorianite. The variegated chemical composition of zirconolites reflects the complex history of the Evate deposit. Compositional and

  9. Zirconium and hafnium

    Science.gov (United States)

    Jones, James V.; Piatak, Nadine M.; Bedinger, George M.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Zirconium and hafnium are corrosion-resistant metals that are widely used in the chemical and nuclear industries. Most zirconium is consumed in the form of the main ore mineral zircon (ZrSiO4, or as zirconium oxide or other zirconium chemicals. Zirconium and hafnium are both refractory lithophile elements that have nearly identical charge, ionic radii, and ionic potentials. As a result, their geochemical behavior is generally similar. Both elements are classified as incompatible because they have physical and crystallochemical properties that exclude them from the crystal lattices of most rock-forming minerals. Zircon and another, less common, ore mineral, baddeleyite (ZrO2), form primarily as accessory minerals in igneous rocks. The presence and abundance of these ore minerals in igneous rocks are largely controlled by the element concentrations in the magma source and by the processes of melt generation and evolution. The world’s largest primary deposits of zirconium and hafnium are associated with alkaline igneous rocks, and, in one locality on the Kola Peninsula of Murmanskaya Oblast, Russia, baddeleyite is recovered as a byproduct of apatite and magnetite mining. Otherwise, there are few primary igneous deposits of zirconium- and hafnium-bearing minerals with economic value at present. The main ore deposits worldwide are heavy-mineral sands produced by the weathering and erosion of preexisting rocks and the concentration of zircon and other economically important heavy minerals, such as ilmenite and rutile (for titanium), chromite (for chromium), and monazite (for rare-earth elements) in sedimentary systems, particularly in coastal environments. In coastal deposits, heavy-mineral enrichment occurs where sediment is repeatedly reworked by wind, waves, currents, and tidal processes. The resulting heavy-mineral-sand deposits, called placers or paleoplacers, preferentially form at relatively low latitudes on passive continental margins and supply 100 percent of

  10. Initial Evaluation of Processing Methods for an Epsilon Metal Waste Form

    Energy Technology Data Exchange (ETDEWEB)

    Crum, Jarrod V.; Strachan, Denis M.; Zumhoff, Mac R.

    2012-06-11

    expected to have a high melting point as well, perhaps exceeding 1500 C. The purpose of the work reported here is to find a potential commercial process with which {var_epsilon}-metal plus other components of UDS can be consolidated into a solid with minimum surface area and high strength Here, we report the results from the preliminary evaluation of spark-plasma sintering (SPS), hot-isostatic pressing (HIP), and microwave sintering (MS). Since bulk {var_epsilon}-metal is not available and companies could not handle radioactive materials, we prepared mixtures of the five individual metal powders (Mo, Ru, Rh, Pd, and Re) and baddeleyite (ZrO{sub 2}) to send the vendors of SPS, HIP, and MS. The processed samples were then evaluated at the Pacific Northwest National Laboratory (PNNL) for bulk density and phase assemblage with X-ray diffraction (XRD) and phase composition with scanning electron microscopy (SEM). Physical strength was evaluated qualitatively. Results of these scoping tests showed that fully dense cermet (ceramic-metal composite) materials with up to 35 mass% of ZrO{sub 2} were produced with SPS and HIP. Bulk density of the SPS samples ranged from 87 to 98% of theoretical density, while HIP samples ranged from 96 to 100% of theoretical density. Microwave sintered samples containing ZrO{sub 2} had low densities of 55 to 60% of theoretical density. Structurally, the cermet samples showed that the individual metals alloyed in to {var_epsilon}-phase - hexagonal-close-packed (HCP) alloy (4-95 mass %), the {alpha}-phase - face-centered-cubic (FCC) alloy structure (3-86 mass %), while ZrO{sub 2} remained in the monoclinic structure of baddeleyite. Elementally, the samples appeared to have nearly uniform composition, but with some areas rich in Mo and Re, the two components with the highest melting points. The homogeneity in distribution of the elements in the alloy is significantly improved in the presence of ZrO{sub 2}. However, ZrO{sub 2} does not appear to react

  11. Initial Evaluation of Processing Methods for an Epsilon Metal Waste Form

    International Nuclear Information System (INIS)

    Crum, Jarrod V.; Strachan, Denis M.; Zumhoff, Mac R.

    2012-01-01

    to have a high melting point as well, perhaps exceeding 1500 C. The purpose of the work reported here is to find a potential commercial process with which (var e psilon)-metal plus other components of UDS can be consolidated into a solid with minimum surface area and high strength Here, we report the results from the preliminary evaluation of spark-plasma sintering (SPS), hot-isostatic pressing (HIP), and microwave sintering (MS). Since bulk (var e psilon)-metal is not available and companies could not handle radioactive materials, we prepared mixtures of the five individual metal powders (Mo, Ru, Rh, Pd, and Re) and baddeleyite (ZrO 2 ) to send the vendors of SPS, HIP, and MS. The processed samples were then evaluated at the Pacific Northwest National Laboratory (PNNL) for bulk density and phase assemblage with X-ray diffraction (XRD) and phase composition with scanning electron microscopy (SEM). Physical strength was evaluated qualitatively. Results of these scoping tests showed that fully dense cermet (ceramic-metal composite) materials with up to 35 mass% of ZrO 2 were produced with SPS and HIP. Bulk density of the SPS samples ranged from 87 to 98% of theoretical density, while HIP samples ranged from 96 to 100% of theoretical density. Microwave sintered samples containing ZrO 2 had low densities of 55 to 60% of theoretical density. Structurally, the cermet samples showed that the individual metals alloyed in to (var e psilon)-phase - hexagonal-close-packed (HCP) alloy (4-95 mass %), the α-phase - face-centered-cubic (FCC) alloy structure (3-86 mass %), while ZrO 2 remained in the monoclinic structure of baddeleyite. Elementally, the samples appeared to have nearly uniform composition, but with some areas rich in Mo and Re, the two components with the highest melting points. The homogeneity in distribution of the elements in the alloy is significantly improved in the presence of ZrO 2 . However, ZrO 2 does not appear to react with the alloy, nor was Zr found in

  12. Zirconium and hafnium in the southeastern Atlantic States

    Science.gov (United States)

    Mertie, J.B.

    1958-01-01

    The principal source of zirconium and hafnium is zircon, though a minor source is baddeleyite, mined only in Brazil. Zircon is an accessory mineral in igneous, metamorphic, and sedimentary rocks, but rarely occurs in hardrock in minable quantities. The principal sources of zircon are therefore alluvial deposits, which are mined in many countries of five continents. The principal commercial deposits in the United States are in Florida, though others exist elsewhere in the southeastern Coastal Plain. The evidence indicates that conditions for the accumulation of workable deposits of heavy minerals were more favorable during the interglacial stages of the Pleistocene epoch than during Recent time. Therefore detrital ores of large volume and high tenor are more likely to be found in the terrace deposits than along the present beaches. Other concentrations of heavy minerals, however, are possible at favored sites close to the Fall Line where the Tuscaloosa formation rests upon the crystalline rocks of the Piedmont province. A score of heavy and semiheavy minerals occur in the detrital deposits of Florida, but the principal salable minerals are ilmenite, leucoxene, rutile, and zircon, though monazite and staurolite are saved at some mining plants. Commercial deposits of heavy minerals are generally required to have a tenor of 4 percent, though ores with a lower tenor can be mined at a profit if the content of monazite is notably high. The percentages of zircon in the concentrates ranges from 10 to 16 percent, and in eastern Florida from 13 to 15 percent. Thus the tenor in zircon of the ore-bearing sands ranges from 0.4 to 0.6 percent. The content of hafnium in zircon is immaterial for many uses, but for some purposes very high or very low tenors in hafnium are required. Alluvial zircon cannot be separated into such varieties, which, if needed, must be obtained from sources in bedrock. It thus becomes necessary to determine the Hf : Zr ratios in zircon from many kinds of

  13. Evaluating crustal contributions to enriched shergottites from the petrology, trace elements, and Rb-Sr and Sm-Nd isotope systematics of Northwest Africa 856

    Science.gov (United States)

    Ferdous, J.; Brandon, A. D.; Peslier, A. H.; Pirotte, Z.

    2017-08-01

    The origin of the incompatible trace element (ITE) characteristics of enriched shergottites has been critical for examining two contradicting scenarios to explain how these Martian meteorites form. The first scenario is that it reflects ITE enrichment in an early-formed mantle reservoir whereas the second scenario attributes it to assimilation of ancient Martian crust (∼4-4.5 Ga) by ITE-depleted magmas. Strongly differentiated shergottite magmas may yield added constraints for determining which scenario can best explain this signature in enriched shergottites. The meteorite Northwest Africa (NWA) 856 is a basaltic shergottite that, unlike many enriched shergottites, lacks olivine and has undergone extensive differentiation from more primitive parent magma. In similarity to other basaltic shergottites, NWA 856 is comprised primarily of compositionally zoned clinopyroxenes (45% pigeonite and 23% augite), maskelynite (23%) and accessory minerals such as ulvöspinel, merrillite, Cl-apatite, ilmenite, pyrrhotite, baddeleyite and silica polymorph. The CI-chondrite normalized rare earth element (REE) abundance patterns for its maskelynite, phosphates, and its whole rock are flat with corresponding light-REE depletions in clinopyroxenes. The 87Rb-87Sr and 147Sm-143Nd internal isochron ages are 162 ± 14 (all errors are ±2σ) Ma and 162.7 ± 5.5 Ma, respectively, with an initial εNdI = -6.6 ± 0.2. The Rb-Sr isotope systematics are affected by terrestrial alteration resulting in larger scatter and a less precise internal isochron age. The whole rock composition is used in MELTS simulations to model equilibrium and fractional crystallization sequences to compare with the crystallization sequence from textural observations and to the mineral compositions. These models constrain the depth of initial crystallization to a pressure range of 0.4-0.5 GPa (equivalent to 34-42 km) in anhydrous conditions at the Fayalite-Magnetite-Quartz buffer, and consistently reproduce the

  14. Extreme isotopologue disequilibrium in molecular SIMS species during SHRIMP geochronology

    Directory of Open Access Journals (Sweden)

    C. W. Magee Jr.

    2017-12-01

    Full Text Available The current limitation in the accuracy and precision of inter-element analysis in secondary ion mass spectrometry (SIMS is the ability to find measurable quantities that allow relative differences in ionization and transmission efficiency of secondary ions to be normalized. In uranium–thorium–lead geochronology, the ability to make these corrections, or "calibrate" the data, results in an accuracy limit of approximately 1 %. This study looks at the ionization of uranium and thorium oxide species, which are traditionally used in U–Pb calibration, to explore the conditions under which isotopologues, or molecular species whose composition differs only in the isotopic composition of one or more atoms in the molecule, remain in or deviate from equilibrium. Isotopologue deficits of up to 0.2 (200 ‰ below ideal mixing are observed in UO2+ species during SIMS gechronological analyses using the SHRIMP IIe SIMS instrument. These are identified by bombarding natural U-bearing minerals with an 18O2− primary beam. The large anomalies are associated with repeat analyses down a single SIMS sputtering crater (Compston et al., 1984, analysis of high-uranium, radiation-damaged zircon, and analysis of baddeleyite. Analysis of zircon under routine conditions yield UO2+ isotopologue anomalies generally within a few percent of equilibrium. The conditions under which the isotopologue anomalies are observed are also conditions in which the UOx-based corrections, or calibration, for relative U vs. Pb ionization efficiencies fail. The existence of these isotopologue anomalies suggest that failure of the various UOx species to equilibrate with each other is the reason that none of them will successfully correct the U  / Pb ratio. No simple isotopologue-based correction is apparent. However, isotopologue disequilibrium appears to be a more sensitive tool for detecting high-U calibration breakdowns than Raman spectroscopy, which showed sharper peaks for

  15. Bulk and Interface Thermodynamics of Calcia-, and Yttria-doped Zirconia Ceramics: Nanograined Phase Stability

    Science.gov (United States)

    Drazin, John Walter

    Calcia-, and yttria- doped zirconia powders and samples are essential systems in academia and industry due to their observed bulk polymorphism. Pure zirconia manifests as Baddeleyite, a monoclinic structured mineral with 7-fold coordination. This bulk form of zirconia has little application due to its asymmetry. Therefore dopants are added to the grain in-order to induce phase transitions to either a tetragonal or cubic polymorph with the incorporation of oxygen vacancies due to the dopant charge mis-match with the zirconia matrix. The cubic polymorph has cubic symmetry such that these samples see applications in solid oxide fuel cells (SOFCs) due to the high oxygen vacancy concentrations and high ionic mobility at elevated temperatures. The tetragonal polymorph has slight asymmetry in the c-axis compared to the a-axis such that the tetragonal samples have increased fracture toughness due to an impact induced phase transformation to a cubic structure. These ceramic systems have been extensively studied in academia and used in various industries, but with the advent of nanotechnology one can wonder whether smaller grain samples will see improved characteristics similar to their bulk grain counterparts. However, there is a lack of data and knowledge of these systems in the nano grained region which provides us with an opportunity to advance the theory in these systems. The polymorphism seen in the bulk grains samples is also seen in the nano-grained samples, but at slightly distinct dopant concentrations. The current theory hypothesizes that a surface excess, gamma (J/m 2), can be added to the Gibbs Free energy equation to account for the additional free energy of the nano-grain atoms. However, these surface energies have been difficult to measure and therefore thermodynamic data on these nano-grained samples have been sparse. Therefore, in this work, I will use a well established water adsorption microcalorimetry apparatus to measure the water coverage isotherms