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Sample records for baddeleyite

  1. Baddeleyite ilmenite deposits from Ukraine and EPR data

    Directory of Open Access Journals (Sweden)

    Леонид Сергеевич Дерский

    2014-08-01

    Full Text Available Metal oxide mineral baddeleyite has been studied. The purpose of this study was investigation of isomorphic impurities in baddeleyite structure. Electron spin resonance metod (ESR was used in this work. ESR signal from Ti3+ ions was detected. Spectroscopic characteristics of this signal are g1=1,997, g2=1,9729 and g3=1,9681. ESR spectrum of baddeleyite has the same characteristics for temperatures T=77K and T=300K.

  2. U-Pb Homogeneity of Duluth Gabbro Baddeleyite from Microgram to Nanogram Scales

    Science.gov (United States)

    Schmitt, A. K.; Chamberlain, K.; Swapp, S. M.; Harrison, T. M.

    2009-12-01

    Baddeleyite has significant potential for U-Pb geochronology of mafic rocks, but due to small crystal sizes it can be exceedingly difficult to extract by conventional mineral separation techniques. We therefore developed in-situ dating of baddeleyite crystals with lateral dimensions between 5 and 20 μm (micro-baddeleyite) in polished petrographic thin sections using a CAMECA ims 1270 ion microprobe, and tested the homogeneity of a baddeleyite standard from Duluth gabbro complex over a wide range of grain sizes. Large (100 - 200 μm in diameter) baddeleyite crystals were separated from sample FC4-b from the Duluth gabbro complex and individually analyzed by isotope dilution thermal ionization mass spectrometry (ID-TIMS). Three FC-4b baddeleyite analyses overlap within error with a weighted mean 207Pb/206Pb date of 1099.6±1.5 Ma that closely agrees with published Duluth gabbro zircon dates. The weighted mean ID-TIMS 206Pb/238U date for FC4-b baddeleyite crystal separates (1096.8±0.3 Ma) is slightly younger than those for zircon. Large FC4-b baddeleyite crystals were also mounted along with pieces of polished thin-sections containing micro-baddeleyite and analyzed by ion microprobe using oxygen flooding to enhance sensitivity for positively charged Pb ions by a factor of ten. Ion microprobe 207Pb/206Pb ages for micro-baddeleyite (average 1096.9±2.6 Ma; MSWD = 1.2; n = 27) agree with the ID-TIMS age. With U-Pb relative sensitivities calibrated on FC4-b crystal separates, the weighted average 206Pb/238U micro-baddeleyite date is 1113±11 Ma (MSWD = 2.6; n = 27). This demonstrates that ion microprobe U-Pb baddeleyite analyses are unbiased by crystallographic orientation or grain size, and that 207Pb/206Pb and 206Pb/238U dates for Precambrian micro-baddeleyite are accurate and precise to within <0.3% and <2% relative uncertainty, respectively. For Phanerozoic samples, we anticipate similar 206Pb/238U age uncertainty if radiogenic yields are high. This opens new

  3. Atom Probe Insights into U-Pb Age Resetting in Baddeleyite

    Science.gov (United States)

    White, L. F.; Reinhard, D.; Moser, D.; Darling, J. R.; Bullen, D.; Prosa, T. J.; Olson, D.; Larson, D. J.; Clifton, P. H.; Lawrence, D.; Martin, I.

    2016-08-01

    Atom probe analysis of highly shocked baddeleyite suggests that igneous crystallisation ages can be isolated from 'partially reset' grains through careful segregation and rejection of planar features known to induce post-impact Pb-diffusion.

  4. 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.

  5. Geochemical features and age of baddeleyite from carbonatites of the Proterozoic Tiksheozero alkaline-ultramafic pluton, North Karelia

    Science.gov (United States)

    Rodionov, N. V.; Belyatsky, B. V.; Antonov, A. V.; Simakin, S. G.; Sergeev, S. A.

    2015-10-01

    On the basis of the local composition, baddeleyite grains that were less altered due to interaction with an alkaline melt and corresponded to the primary stage of crystallization of the intrusion were selected from the carbonatite intrusion of the Proterozoic polyphase Tiksheozero alkaline-ultramafic complex. The single age of carbonatite crystallization characterized of the bulk volume of the intrusion was estimated for the first time on the basis of 40 local U-Th-Pb (SHRIMP II) analyses of these grains. The overall concordant age of baddeleyite is 1994.8 ± 9.4 Ma, and the lower age limit of the polyphase complex formation is less than 1998.4 ± 3.5 Ma.

  6. Variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite NWA 5298 and improved U-Pb dating of Solar System events

    Science.gov (United States)

    Darling, James R.; Moser, Desmond E.; Barker, Ivan R.; Tait, Kim T.; Chamberlain, Kevin R.; Schmitt, Axel K.; Hyde, Brendt C.

    2016-06-01

    The accurate dating of igneous and impact events is vital for the understanding of Solar System evolution, but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole-rock isotopic systems used for geochronology. Baddeleyite (monoclinic ZrO2) is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust U-Pb isotopic systematics, but there is little understanding of shock-effects on this phase. Here we present new nano-structural measurements of baddeleyite grains in a thin-section of the highly-shocked basaltic shergottite Northwest Africa (NWA) 5298, using high-resolution electron backscattered diffraction (EBSD) and scanning transmission electron microscopy (STEM) techniques, to investigate shock-effects and their linkage with U-Pb isotopic disturbance that has previously been documented by in-situ U-Pb isotopic analyses. The shock-altered state of originally igneous baddeleyite grains is highly variable across the thin-section and often within single grains. Analyzed grains range from those that preserve primary (magmatic) twinning and trace-element zonation (baddeleyite shock Group 1), to quasi-amorphous ZrO2 (Group 2) and to recrystallized micro-granular domains of baddeleyite (Group 3). These groups correlate closely with measured U-Pb isotope compositions. Primary igneous features in Group 1 baddeleyites (n = 5) are retained in high shock impedance grain environments, and an average of these grains yields a revised late-Amazonian magmatic crystallization age of 175 ± 30 Ma for this shergottite. The youngest U-Pb dates occur from Group 3 recrystallized nano- to micro-granular baddeleyite grains, indicating that it is post-shock heating and new mineral growth that drives much of the isotopic disturbance, rather than just shock deformation and phase transitions. Our data demonstrate that a systematic multi-stage microstructural evolution in

  7. Zircon and baddeleyite U-Pb geochronology and Hf isotopes from the Central Atlantic Magmatic Province (CAMP)

    Science.gov (United States)

    Davies, Joshua; Marzoli, Andrea; Bertrand, Herve; Youbi, Nasrrddine; Schaltegger, Urs

    2016-04-01

    Large Igneous Provinces (LIPs) are anomalously large volumes of dominantly mafic magma that erupted and intruded into the upper crust over short time scales. The origin of these volcanic provinces is very likely specific for each case, partly explained by plate tectonic processes or mantle plumes. Despite an ambivalent plate tectonic connection, there is a striking temporal correlation between the timing of LIPs and periods of mass extinction on Earth. However, establishing the relationship between these two is quite complicated since mass extinctions are typically recognised in the marine record, and LIPs are usually terrestrially emplaced. High precision geochronology of LIPs is essential to (i) establish the synchrony and infer the causal relationship with mass extinctions, and (ii) to understand how LIPs form. In this study, we apply high-precision zircon and baddeleyite U-Pb geochronology to rocks from the ~200 Ma Central Atlantic Magmatic Province (CAMP), in an attempt to reconstruct the overall timing of the event, its spatial distribution in time, and determine its relationship with the end-Triassic mass extinction. We also present Hf isotope data from the separated zircon and baddeleyite to both elucidate the origin of the LIP and also to determine if the magmas all originate from the same source. Our data suggest that the majority of the CAMP magmas were emplaced over a 0.5 Ma period from ~201.5 Ma to ~201.0 Ma with a possible small secondary event occurring much later at ~199 Ma. Spatially, it appears that CAMP magmatism occurred roughly simultaneously over the entire province (i.e. ~8000 Km North to South). However, the Hf isotopic composition varies over this length with the highest values (~5.5 ɛHf) occurring in a small area to the south of the province in Brazil and Sierra Leone. Towards the north, the ɛHf values become negative, indicating the presence of an older or more enriched component in the magmas. Our geochronology also indicates that CAMP

  8. U-Pb baddeleyite ages for the Scourie dyke swarm, Scotland: evidence for two distinct intrusion events

    Science.gov (United States)

    Heaman, L. M.; Tarney, J.

    1989-08-01

    PRECISE and accurate radiometric ages for continental mafic dyke swarms are a prerequisite for global correlation of mafic magmatic events, calibration of apparent polar-wander paths and deciphering mechanisms of dyke emplacement. Precambrian dyke swarms, such as the Scourie dyke swarm in north-west Scotland, are invaluable time-markers, so that a precise and accurate knowledge of their emplacement age is critical when unravelling the complex geological evolution of many terrains. Precise dating is often difficult, however, because magma interaction with country rock and subsequent metamorphic events can severely perturb some isotopic systems. Recent advances in U-Pb geochronology1-3 combined with the discovery that some mafic dykes contain trace amounts of uranium-bearing minerals such as baddeleyite (ZrO2) and/or zircon have made it possible to obtain U-Pb ages for these rocks with a precision typically on the order of 1-2 Myr4,5. Some of the first detailed U-Pb studies of Precambrian mafic dyke swarms5,6 have shown that large volumes of mafic magma, 100,000 km3, were emplaced into the continental crust in surprisingly short periods of time (<2 Myr). Here we report the results from a U-Pb study of three members of the Scourie dyke swarm, and find at least two periods of dyke emplacement at 2,418 and 1,992 Myr BP. We speculate on a potential global correlation of early Proterozoic mafic magmatism and hence on the origin of dyke swarms.

  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. Exploring the pre-eruptive history of the Central Atlantic Magmatic Province (CAMP) and the link with the end Triassic extinction using high precision U-Pb zircon and baddeleyite geochronology

    Science.gov (United States)

    Davies, Joshua; Marzoli, Andrea; Bertrand, Hervé; Youbi, Nasrrddine; Schaltegger, Urs

    2015-04-01

    The Central Atlantic Magmatic Province (CAMP) is a massive outpouring of basaltic lava, dykes and sills that was predominantly emplaced into the Triassic-Jurassic basins of North and South America, Europe and Africa. These basins were, at the time, in the center of the paleo-supercontinent Pangea, and the CAMP flood basalts are associated with Pangea's break-up and the opening of the Atlantic Ocean. The global climatic and environmental impact of the basalt eruption has been temporally linked with the end-Triassic mass extinction, although the extinction horizon, defined by a carbon isotope excursion, is stratigraphically below the first basaltic flows in all of the currently identified basins. Therefore, if the extinction is related to the CAMP, it must be related to a process that occurred before the eruption of the first basalt flow, or is co-incident with a currently unidentified older basalt flow. Here we present high precision TIMS zircon U-Pb geochronology on zircons from the North Mountain basalt (NMB) in the Fundy basin, Canada, and also baddeleyite from the Foum Zuid dyke (FZD) in the Anti-Atlas, Morocco. The NMB zircons have been separated from the lowermost accessible basalt flow of the NMB sequence in a coarse-grained section, rather than from a felsic residual melt pod, which is the usual target for zircon geochronology in basalts. The baddeleyites from the FZD were also separated from a coarse-grained section of the dyke. The zircons and baddeleyites from the NMB and FZD samples contain an antecrystic population with ages more than 1 Ma older than the emplacement of the basalts. The U-Pb ages presented here suggest that there was magmatic activity relating to the CAMP before the eruption of the first basalts. There are a number of possible explanations for the old zircons 1) recycling of zircon from earlier phases of magmatism, which then would have to have been re-molten and entrained into the NMB and FZD magmas. 2) Recycling of crystal mush from

  11. U-Pb (ID-TIMS) baddeleyite ages and paleomagnetism of 1.79 and 1.59 Ga tholeiitic dyke swarms, and position of the Rio de la Plata Craton within the Columbia supercontinent

    Science.gov (United States)

    Teixeira, Wilson; D'Agrella-Filho, Manoel S.; Hamilton, Mike A.; Ernst, Richard E.; Girardi, Vicente A. V.; Mazzucchelli, Maurizio; Bettencourt, Jorge S.

    2013-08-01

    The Tandilia Terrane (southernmost fringe of the Rio de la Plata Craton) is an igneous and metamorphic complex produced by an accretionary orogeny (2.25-2.02 Ga). Calc-alkaline acidic dykes with E-W strike and a major shear zone with similar orientation are related with the late orogeny stage, as supported by field relations. In a previous study the acid dykes gave 40A-39Ar ages of 2007 ± 24 Ma to 2020 ± 24 Ma. A N and NW trending tholeiitic dyke swarm (Tandil swarm) is also present in the Tandilia Terrane. One sample from the NW-trending subset previously gave a U-Pb (ID-TIMS) baddeleyite age of 1588 ± 11 Ma. New precise U-Pb (ID-TIMS) baddeleyite dating of both N- and NW-trending Tandil dykes yielded crystallization ages of 1589 ± 3 Ma, 1588 ± 3 Ma and 1588 ± 3 Ma. Significantly older tholeiitic dykes known as the Florida swarm occur in the Northern Rio de la Plata Craton, for which a U-Pb (ID-TIMS) baddeleyite age of 1790 ± 5 Ma was previously reported. Consequently intermittent rifting (1.79, 1.59 Ga) took place after tectonic stabilization of the late Paleoproterozoic lithosphere (proto-Rio de la Plata Craton). The available geochemical data for the 1.59 Ga Tandil dykes define low- and high-TiO2 trends, although, only the low-TiO2 subgroup is firmly dated. Both the Tandil and Florida dykes have geochemical and Nd-Sr characteristics consistent with derivation from heterogeneous mantle sources that underwent metasomatic effects. The Tandil dykes may be linked with the 1.57 ± 0.02 Ga Capivarita anorthosite which occurs to the east of the northern part of the craton. Correlatives on other crustal blocks may include those in Baltica such as bimodal rock association (including the Breven-Hällefors and Åland-Åboland diabase dykes) and in the reconstructed Gawler Craton/NW Laurentia dolerites, bimodal magmatism and IOCG deposits. Contemporary within-plate bimodal associations are also present in the SW Amazonian Craton. Paleomagnetic data for the 1790 Ma

  12. Zircon and baddeleyite U-Pb geochronology of the Shennongjia Group in the Yangtze Craton and its tectonic significance%扬子克拉通神农架群锆石和斜锆石U-Pb年代学及其构造意义

    Institute of Scientific and Technical Information of China (English)

    李怀坤; 张传林; 相振群; 陆松年; 张健; 耿建珍; 瞿乐生; 王志先

    2013-01-01

    The Shennongjia Group, spreading on the northern margin of the Yangtze Craton, is a well-preserved succession of the Mesoproterozoic strata in South China, unconformably overlain by the Macaoyuan Group. Zircon and baddeleyite U-Pb dating results of dolarenite, tuff of the Shennongjia Group and mafic dike intruding the Shennongjia Group are reported in this paper. The dating results demonstrate that there are four age peaks 1.4Ga, 1. 8Ga, 2. OGa and 2. 7Ga in the detrital zircon age spectra of the Dayanping Formation of the Lower Shennongjia Group. The zircon U-Pb age of the tuff of the Yemahe Formation in the upper part of the Shennongjia Group is ca. 1220Ma. The baddeleyite and zircon U-Pb ages of the mafic dike intruding the Shicaohe Formation are lllSMa and 1083Ma respectively. Based on our new age data, combining with the regional geological setting analysis, we arrive at the following preliminary conclusions. (1) The age span of the Shennongjia Group can be precisely put in 1. 4 ~ 1. 1Ga; the sedimentary materials of the Shennongjia Group came mainly from the ancient basement of the Yangtze Craton with minor probably from the Cathaysian or Laurentian. (2) The unconformity between the Shennongjia Group and the overlying Macaoyuan Group was formed at about 1.1 ~ 1. 0Ga probably in the process of the initial assembly between the Yangtze Craton and the Cathaysia Massif, which might be the tectonic response of the Rodinia supercontinental assembly event ( 3 ) The emplacing time of the mafic dike intruding the Shicaohe Formation is 1115 ~ 1083Ma; coeval mafic intrusion events are widespread in Laurentia, Africa, Australia and Antarctica. It is still an unresolved problem whether this phase mafic intrusion event in the Shennongjia area resulted from the Rodinia supercontinental assembly or was genetically related with the coeval global-scale mantle plume. (4) The determination of the sedimentation age of the Shennongjia Group provides a potential candidate for

  13. 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

    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....

  14. 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...

  15. Stability of rutile-type TiO sub 2 under high pressure

    CERN Document Server

    Sasaki, T

    2002-01-01

    The high-pressure phases of TiO sub 2 have been investigated theoretically on the basis of first-principles density functional theory. Both the equation of states of the low-pressure phase and the structural phase transitions (the rutile-to-alpha-PbO sub 2 -type and alpha-PbO sub 2 -to-baddeleyite transitions) were successfully explained in agreement with previous experiments. The calculation suggests the possibility that the high-pressure phase next to the baddeleyite phase does not have the brookite structure, which has been observed in ZrO sub 2 and HfO sub 2. Furthermore, the stability of the low-pressure phases in TiO sub 2 was discussed on the basis of the atomic electronic structure.

  16. Rietveld analysis of ceramic nuclear waste forms

    Energy Technology Data Exchange (ETDEWEB)

    White, T.J. [Univ. of South Australia, Ingle Farm (Australia); Mitamura, H. [Japan Atomic Energy Research Institute, Ibaraki (Japan)

    1994-12-31

    Powder X-ray diffraction patterns were collected from three titanate waste forms - a calcine powder, a prototype ceramic without waste, and a ceramic containing 10 wt% JW-A simulated waste - and interpreted quantitatively using the Rietveld method. The calcine consisted of fluorite, pyrochlore, rutile, and amorphous material. The prototype waste form contained rutile, hollandite, zirconolite and perovskite. The phase constitution of the JW-A ceramic was freudenbergite, loveringite, hollandite, zirconolite, perovskite and baddeleyite. Procedures for the collection of X-ray data are described, as are assumptions inherent in the Rietveld approach. A selection of refined crystal data are presented.

  17. 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.

  18. Mineral chemistry of a zircon-bearing, composite, veined and metasomatised upper-mantle peridotite xenolith from kimberlite

    Science.gov (United States)

    Dawson, J. B.; Hill, P. G.; Kinny, P. D.

    2001-02-01

    Zircon-bearing veins in a harzburgite xenolith from kimberlite have imposed Ca-metasomatism on the harzburgite wall rock, in addition to adding K, Fe, Ti and OH. The zircon, previously dated to have an age similar to that of the xenolith-hosting kimberlite, shows higher Y, Nb, Ba, REE, Th and U contents than other mantle-derived zircons. Peripheral alteration of the zircon to baddeleyite and zirconolite, and alteration of vein ilmenite to perovskite suggest reaction with an evolving carbonatitic kimberlite melt. The high Cr2O3 content (0.77 wt%) of the zirconolite extends the compositional range of terrestrial zirconolite.

  19. 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

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

    International Nuclear Information System (INIS)

    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

  1. Pressure-induced amorphization and polyamorphism in one-dimensional single crystal TiO2 nanomaterials

    OpenAIRE

    Li, Quanjun; Bingbing LIU; Wang, Lin; Li, Dongmei; LIU, RAN; Zou, Bo; Cui, Tian; Zou, Guangtian; Meng, Yue; Mao, Ho-kwang; Liu, Zhenxian; Jing LIU; Li, Jixue

    2012-01-01

    The structural phase transitions of single crystal TiO2-B nanoribbons were investigated in-situ at high-pressure using the synchrotron X-ray diffraction and the Raman scattering. Our results have shown a pressure-induced amorphization (PIA) occurred in TiO2-B nanoribbons upon compression, resulting in a high density amorphous (HDA) form related to the baddeleyite structure. Upon decompression, the HDA form transforms to a low density amorphous (LDA) form while the samples still maintain their...

  2. SIMS Pb/Pb dating of Zr-rich minerals in lunar meteorites Miller Range 05035 and LaPaz Icefield 02224:Implications for the petrogenesis of mare basalt

    Institute of Scientific and Technical Information of China (English)

    HSU; WeiBiao

    2010-01-01

    Miller Range (MIL) 05035 and LaPaz Icefield (LAP) 02224 are unbrecciated lunar basalt meteorites. In this report, we studied their petrography and mineralogy and made in situ uranogenic Pb/Pb dating of Zr-rich minerals. Petrography and mineralogy of these two lunar meteorites are consistent with previous investigations. The zirconolite Pb/Pb age of MIL 05035 is 3851±8 Ma (2σ), in excellent agreement with previous reports. This age suggests that MIL 05035 could be paired with Asuka 881757, a low-Ti mare basalt meteorite. The magmatic event related to MIL 05035 was probably due to the late heavy impact bom- bardment on the moon around 3.9 Ga. One baddeleyite grain in LAP 02224 shows a large variation of Pb/Pb age, from 3109±29 to 3547±21 Ma (2σ), much older than the whole-rock age of the same meteorite (~3.02±0.03 Ga). The other baddeleyite grain in LAP 02224 has an age of 3005±17 Ma (2σ). The result indicates that the minimum crystallization age of LAP 02224 is ~3.55 Ga and the younger ages could reflect late thermal disturbance on U-Pb system.

  3. 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)

  4. Microscopic characterization of crystalline phases in waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Buck, E.C.; Dietz, N.L.; Wronkiewicz, D.J.; Bates, J.K. [Argonne National Lab., IL (United States); Millar, A. [Purdue Univ., West Lafayette, IN (United States)

    1995-07-01

    Transmission electron microscopy (TEM) has been used to determine the microstructure of crystalline phases present in zirconium- and titanium-bearing glass crystalline composite (GCC) waste forms. The GCC materials were found to contain spinels (maghemite), zirconolites, perovskites (CaTiO{sub 3}) and plagiociase feldspar (anorthite) mineral phases. The structure of the uranium and cerium-bearing monoclinic zirconolite was characterized by medium resolution TEM imaging and electron and X-ray diffraction (XRD). The phase was found to contain high levels of iron in comparison to Synroc-type zirconolites. Excess zirconium in zirconolite has resulted in martensitic baddeleyite (ZrO{sub 2}) formation. Anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}) was present as elongated crystallites within a calcium-rich aluminosilicate glass. Lead and iron-bearing anorthite lying along distinct precipitates were occasionally observed within the an crystallographic planes.

  5. Partial pressures of oxygen, phosphorus and fluorine in some lunar lavas

    Science.gov (United States)

    Nash, W. P.; Hausel, W. D.

    1973-01-01

    Lunar sample 14310 is a feldspar-rich basalt which shows no evidence of shock deformation or recrystallization. Pyroxenes include Mg-rich orthopyroxene, pigeonite and augite; pyroxferroite occurs in the interstitial residuum. Plagioclase feldspars are zoned from An(96) to An(67), and variations in feldspar compositions do not necessarily indicate loss of Na during eruption of the lava. Opaque phases include ilmenite, ulvospinel, metallic iron, troilite, and schreibersite. Both whitlockite and apatite are present, and the interstitial residua contain baddeleyite, tranquillityite and barium-rich sanidine. Theoretical calculations provide estimates of partial pressures of oxygen, phosphorus, and fluorine in lunar magmas. In general, partial pressures of oxygen are restricted by the limiting assemblages of iron-wuestite and ilmenite-iron-rutile; phosphorus partial pressures are higher in lunar magmas than in terrestrial lavas. The occurrence of whitlockite indicates significantly lower fugacities of fluorine in lunar magmas than in terrestrial magmas.

  6. Synthesis and Characterization of A Novel Bio Ceramic Composite in The Lime-Magnesia-Silica Ternary System With ZrO2 Additive

    International Nuclear Information System (INIS)

    In-situ diopside-wollastonite-akermanite-baddeleyite (DWAB) as a new bio ceramic composite was developed in the lime-magnesia-silica system with zirconia additive. The processing and sintering were achieved via solid-state reaction. The raw materials we mixed, compacted and sintered at 1300°C for 2 h. Phase composition, macrostructure physical and mechanical properties of the produced sintered samples were determine Also, the in-vitro bioactivity of the sintered composite was investigated by the analysis of its apatite-formation ability in the simulated body fluid (SBF) using SEM-EE analysis. The results indicated that the composite possess high Vickers hardness ai fracture toughness of about 3 GPa and 2 MPa. m1/2, respectively. In addition, apatil forming ability of this composite was relatively found to be similar to wollastonite ai much faster than diopside and akermanite

  7. Properties of hydrogen permeation barrier on the surface of zirconium hydride

    Institute of Scientific and Technical Information of China (English)

    CHEN Weidong; WANG Lijun; HAN Lin; CHEN Song

    2008-01-01

    A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen.A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment.The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa.The oxide film is composed of two layers,a permeable oxide layer and a dense oxide layer,and the main phase of the oxide film is ZrO2 with baddeleyite structure.The XPS analysis shows that O-H bonds exist in the oxide film,which are helpful for resisting hydrogen diffusion through the oxide film.

  8. 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)

    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

  9. Purification of zirconium concentrates

    International Nuclear Information System (INIS)

    A commercial grade ZrO2 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% ZrO2 and 0,3% U3O8. 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-HNO3-H2O system. The raffinate containing zirconium + impurities (aluminium, iron and titanium) was purified by an ion exchange operation using a strong cationic resin

  10. 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.

  11. Integrated Paleomagnetism and U-Pb Geochronology of Mafic Dikes of the Eastern Anabar Shield Region, Siberia: Implications for Mesoproterozoic Paleolatitude of Siberia and Comparison with Laurentia.

    Science.gov (United States)

    Ernst; Buchan; Hamilton; Okrugin; Tomshin

    2000-07-01

    This article reports the first joint paleomagnetic and U-Pb geochronologic study of Precambrian diabase dikes in the Anabar Shield and adjacent Riphean cover of Siberia. It was undertaken to allow comparison with similar published studies in Laurentia and to test Proterozoic reconstructions of Siberia and Laurentia. An east-trending Kuonamka dike yielded a provisional U-Pb baddeleyite emplacement age of 1503+/-5 Ma and a virtual geomagnetic pole at 16 degrees S, 221 degrees E (dm=17&j0;, dp=10&j0;). A paleomagnetic pole at 6 degrees N, 234 degrees E (dm=28&j0;, dp=14&j0;) was obtained from five Kuonamka dikes. An east-southeast-trending Chieress dike yielded a U-Pb baddeleyite emplacement age of 1384+/-2 Ma and a virtual geomagnetic pole at 4 degrees N, 258 degrees E (dm=9&j0;, dp=5&j0;). Kuonamka and Chieress poles are interpreted to be primary but do not average out secular variation. Assuming that the Siberian Plate has remained intact since the Mesoproterozoic, except for mid-Paleozoic opening of the Viljuy Rift, then the above results indicate that the Siberian Plate was in low latitudes at ca. 1503 and 1384 Ma, broadly similar to low latitudes determined for Laurentia from well-dated paleopoles at 1460-1420, 1320-1290, and 1267 Ma. This would allow Laurentia and Siberia to have been attached in the Mesoproterozoic, as suggested in several recent studies based on geological criteria. However, because paleomagnetic results from the Anabar Shield region do not average out secular variation and the ages of poles from Siberia and Laurentia are not well matched, it is not yet possible to distinguish between these reconstructions or to rule out other configurations that also maintain the two cratons at low paleolatitudes.

  12. A systematic evaluation of the Zr-in-rutile thermometer in ultra-high temperature (UHT) rocks

    Science.gov (United States)

    Pape, Jonas; Mezger, Klaus; Robyr, Martin

    2016-05-01

    The Zr-in-rutile geothermometer is potentially a widely applicable tool to estimate peak metamorphic temperatures in rocks from diverse geological settings. In order to evaluate its usefulness and reliability to record and preserve high temperatures in granulite facies rocks, rutile from UHT rocks was investigated to assess different mechanisms of Zr (re-)distribution following cooling from high temperature. Granulite facies paragneisses from the lowermost part of the Ivrea Zone, Italy, incorporated as thin sheets into the extensive basaltic body of the Mafic Complex were selected for this study. The results show that Zr-in-rutile thermometry, if properly applied, is well suited to identify and study UHT terranes as it preserves a record of temperatures up to 1190 °C, although the thermometer is susceptible to partial post-peak metamorphic resetting by Zr diffusion. Texturally homogeneous rutile grains preserve Zr concentrations corresponding to temperatures of prograde rutile growth. Diverse rutile textures and relationships between some rutile host grains and included or adjacent Zr-bearing phases bear testimony to varying mechanisms of partial redistribution and resetting of Zr in rutile during cooling and link Zr-in-rutile temperatures to different steps of the metamorphic evolution. Rutile grains that equilibrated their Zr concentrations at temperatures above 1070 °C (i.e. 1.1 wt% Zr) could not retain all Zr in the rutile structure during cooling and exsolved baddeleyite (ZrO2). By subsequent reaction of baddeleyite exsolution lamellae with SiO2, zircon needles formed before the system finally closed at 650-700 °C without significant net loss of Zr from the whole host rutile grain. By reintegration of zircon exsolution needles, peak metamorphic temperatures of up to 1190 °C are derived for the studied rocks, which demonstrates the suitability of this solution thermometer to record UHT conditions and also confirms the extraordinary geological setting of the

  13. The Catanda extrusive carbonatites (Kwanza Sul, Angola): an example of explosive carbonatitic volcanism

    Science.gov (United States)

    Campeny, Marc; Mangas, José; Melgarejo, Joan C.; Bambi, Aurora; Alfonso, Pura; Gernon, Thomas; Manuel, José

    2014-04-01

    Carbonatite lavas and pyroclastic rocks are exposed in the volcanic graben of Catanda and represent the only known example of extrusive carbonatites in Angola. A new detailed geological map of the area is presented in this study as well as six different stratigraphic sections. Pyroclastic rocks, apparently unwelded, are dominant in the area and represented in all the stratigraphic columns. They form shallowly to moderately inclined layers, mostly devoid of internal structures, that range in thickness from several centimetres to metres. They are dominantly lapilli tuffs and minor tuffs occasionally comprising pelletal lapilli. Based on their different features and field relationships, at least five different pyroclastic lithofacies have been distinguished in the area. Carbonatitic lavas outcrop in the external parts of the Catanda graben, forming coherent layers interbedded with pyroclastic rocks. Calcite is the most common mineral in the lavas, but other accessory minerals such as fluorapatite, titaniferous magnetite, phlogopite, pyrochlore, baddeleyite, monticellite, perovskite, cuspidine and periclase have also been identified. At least four different types of lavas have been distinguished based on their mineral associations and textural features. This study reveals an overall abundance of pyroclastic material in comparison to lava flows in the Catanda area, suggesting that eruptive processes were dominated by explosive activity similar to what has been described in other carbonatite and kimberlite localities. The Catanda carbonatitic volcanism was associated with monogenetic volcanic edifices with tuff ring or maar morphologies, and at least seven possible eruptive centres have been identified in the area.

  14. New paleomagnetic data from 1.80-1.75 Ga mafic intrusions of Fennoscandia and Sarmatia: implications for the late Paleoproterozoic paleogeography of Baltica and Laurentia

    Science.gov (United States)

    Pisarevsky, Sergei; Lubnina, Natalia; Sokolov, Svetoslav; Bogdanova, Svetlana

    2016-04-01

    A series of recently dated 1.78-1.75 Ga lamprophyre and shoshonite intrusions are exposed north of Ladoga Lake in southern Karelia (Fennoscandia). We carried out a paleomagnetic study of these intrusions and an additional study of the coeval gabbro-dolerite Ropruchey sill near the Onega Lake. All studied rocks carry a stable primary remanence supported by positive contact tests. We also studied 14 mafic dykes and 1 mafic sill from Ukrainian shield (Sarmatia). Most of these intrusions have been dated or re-dated recently by U-Pb (baddeleyite) method at 1.80-1.75 Ga. Ukrainian dykes also carry a consistent stable bipolar remanence. Two positive contact tests suggest that this remanence is primary. A comparison of new and previously published paleomagnetic data shows a significant difference between Fennoscandian and Sarmatian 1.80-1.75 Ga paleopoles. This implies that the final assemble of Baltica by docking of Volgo-Sarmatia and Fennoscandia occurred after 1.75 Ga. Consequently these two parts of Baltica should be considered as independent blocks in pre-1.75 Ga paleogeographic reconstructions. Using late Paleoproterozoic paleomagnetic data from Laurentia together with geological constraints we have built a new kinematic paleogeographic model for Laurentia and Baltica in the Statherian.

  15. Zirconia ceramics for excess weapons plutonium waste

    Science.gov (United States)

    Gong, W. L.; Lutze, W.; Ewing, R. C.

    2000-01-01

    We synthesized a zirconia (ZrO 2)-based single-phase ceramic containing simulated excess weapons plutonium waste. ZrO 2 has large solubility for other metallic oxides. More than 20 binary systems A xO y-ZrO 2 have been reported in the literature, including PuO 2, rare-earth oxides, and oxides of metals contained in weapons plutonium wastes. We show that significant amounts of gadolinium (neutron absorber) and yttrium (additional stabilizer of the cubic modification) can be dissolved in ZrO 2, together with plutonium (simulated by Ce 4+, U 4+ or Th 4+) and impurities (e.g., Ca, Mg, Fe, Si). Sol-gel and powder methods were applied to make homogeneous, single-phase zirconia solid solutions. Pu waste impurities were completely dissolved in the solid solutions. In contrast to other phases, e.g., zirconolite and pyrochlore, zirconia is extremely radiation resistant and does not undergo amorphization. Baddeleyite (ZrO 2) is suggested as the natural analogue to study long-term radiation resistance and chemical durability of zirconia-based waste forms.

  16. Structural, elastic, electronic and optical properties of various mineral phases of TiO2 from first-principles calculations

    Science.gov (United States)

    Liu, Qi-Jun; Zhang, Ning-Chao; Liu, Fu-Sheng; Liu, Zheng-Tang

    2014-07-01

    Titanium dioxide is well known as a semiconductor material, which attracts a great deal of attention for promising applications in many fields due to its outstanding physical and chemical properties. To investigate the structural, elastic, mechanical, electronic and optical properties of various TiO2 phases systematically, we present the ultrasoft pseudopotential planewave method within local density approximation and generalized gradient approximation, as well as the norm-conserving pseudopotential within hybrid functional B3LYP by first-principles calculations on fluorite, pyrite, rutile, anatase, hollandite, brookite, columbite, cotunnite, bronze and baddeleyite TiO2 phases. The structural parameters of ten phases are calculated, which are shown to be consistent with previous theoretical and experimental data. We obtain the elastic constants of ten phases and then estimate the bulk, shear and Young’s moduli, Poisson’s coefficient and Lamé’s constants using the Voigt-Reuss-Hill approximation. The energy band structures, density of states and charge populations of ten phases were obtained and indicated there is covalency in TiO2. Moreover, the complex dielectric function, refractive index and extinction coefficient of the ten phases were calculated; this data can aid future experimental research.

  17. 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.

  18. Contributions of zircon U-Pb geochronology to understanding the volcanic and sedimentary history of some Purāna basins, India

    Science.gov (United States)

    Basu, Abhijit; Bickford, Marion. E.

    2014-09-01

    In this century, U-Pb ages of magmatic and detrital zircons, together with a few less accurate but fairly robust ages determined on monazite and baddeleyite, in the Purāna successions in India have established a few firm timelines that constrain the opening, closure, inversion, and provenance of the Purāna basins. The Cuddapah basin opened shortly before ca. 1900 Ma, the Vindhyan basin opened before ca. 1630 Ma, the Khariar basin likely opened ca. 1500 Ma, and the Chhattisgarh basin opened ca. 1400 Ma. The Marwar basin opened after ca. 750 Ma. The Chhattisgarh basin began to invert at ca. 1000 Ma and closed shortly thereafter. The Indravati and the Vindhyan basins closed ca. 1000 Ma. There are no other defensible geochronologic data to adequately constrain the opening and closure of other Purāna basins (e.g., Kaladgi, Badami, Bhima, Kurnool, Mallampalli, Albaka, Ampani, Sabari, and Kolhan). Neither the fossil record nor the biostratigraphy of these basins necessarily correspond to the chronology determined through radiometric measurements. The discovery of ca. 1000 Ma volcanic events in the Indravati and Chhattisgarh basins adds to the growing list of ca. 1000 Ma thermal disturbances in the Indian shield. Most of these events were likely the far field effects of the final assembly of Rodinia.

  19. Radioactivity in raw materials and end products in the Italian ceramics industry

    International Nuclear Information System (INIS)

    The natural radioactivity due to the presence of 238U, 232Th and 40K in zirconium minerals (zircon and baddeleyite) used in the Italian ceramics industry, in tiles and in waste sludges resulting from ceramic processes, has been measured. The measurements were made by γ-ray spectrometry with a high-purity germanium (HPGe) detector connected to a multichannel analyser. The average concentrations of 238U and 232Th observed in the mineral samples (>3000 and >500 Bq kg-1, respectively) are higher than the concentrations found in the earth's crust by one or two orders of magnitude. The specific activities of tiles and sludges are much lower than in zirconium minerals. The 238U and 232Th concentrations in tiles (50-79 and 52-66 Bq kg-1, respectively) are not higher than in other building materials. The 238U concentration of sludges (116-193 Bq kg-1) is 4-6 times higher than the mean value for the earth's crust. The results are examined on the basis of the existing Italian legislation (D.Lgs no. 230, 1995, Gazzetta Ufficiale 13/06/1996, no. 136, Supplemento Ordinario, Rome, Italy) and the EC Directive no. 29/Euratom of the year 1996 (Gazzetta Ufficiale della Communita Europea 29/06/1996, no. L159)

  20. Pressure-Induced Amorphization and Polyamorphism in One-Dimensional Single-Crystal TiO[subscript 2] Nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Li, Quanjun; Liu, Bingbing; Wang, Lin; Li, Dongmei; Liu, Ran; Zou, Bo; Cui, Tian; Zou, Guangtian; Meng, Yue; Mao, Ho-kwang; Liu, Zhenxian; Liu, Jing; Li, Jixue (Jilin); (CIW); (Chinese Aca. Sci.)

    2010-02-11

    The structural phase transitions of single-crystal TiO{sub 2}-B nanoribbons were investigated in situ at high pressure using synchrotron X-ray diffraction and Raman scattering. Our results have shown a pressure-induced amorphization (PIA) occurred in TiO{sub 2}-B nanoribbons upon compression, resulting in a high-density amorphous (HDA) form related to the baddeleyite structure. Upon decompression, the HDA form transforms to a low-density amorphous (LDA) form, while the samples still maintain their pristine nanoribbon shape. A high-resolution transmission electron microscopy (HRTEM) image reveals that the LDA phase has an {alpha}-PbO{sub 2} structure with short-range order. We propose a homogeneous nucleation mechanism to explain the pressure-induced amorphous phase transition in the TiO{sub 2}-B nanoribbons. Our study demonstrates for the first time that PIA and polyamorphism occurred in the one-dimensional (1D) TiO{sub 2} nanomaterials and provides a new method for preparing 1D amorphous nanomaterials from crystalline nanomaterials.

  1. Zirconium - an imported mineral commodity

    International Nuclear Information System (INIS)

    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

  2. Volcanic sanidinites: an example for the mobilization of high field strength elements (HFSE) in magmatic systems

    Science.gov (United States)

    Aßbichler, Donjá; Heuss-Aßbichler, Soraya; Müller, Dirk; Kunzmann, Thomas

    2016-04-01

    In earth science the mobility of high field strength elements (HFSE) is generally discussed in context of hydrothermal processes. Recent investigations mainly address processes in (late) magmatic-, metamorphic- and submarine hydrothermal systems. They have all in common that H2O is main solvent. The transport of HFSE is suggested to be favored by volatiles, like boron, fluorine, phosphate and sulfate (Jiang et al., 2005). In this study processes in magmatic system are investigated. Sanidinites are rare rocks of igneous origin and are found as volcanic ejecta of explosive volcanoes. They consist mainly of sanidine and minerals of the sodalite group. The very porous fabric of these rocks is an indication of their aggregation from a gaseous magmatic phase. The large sanidine crystals (up to several centimeters) are mostly interlocking, creating large cavities between some crystals. In these pores Zr crystallizes as oxide (baddeleyite, ZrO2) or silicate (zircon, ZrSiO4). The euhedral shape of these minerals is a further indication of their formation out of the gas phase. Furthermore, bubbles in glass observed in some samples are evidence for gas-rich reaction conditions during the formation of the sanidinites. The formation of sanidinites is suggested to be an example for solvothermal processes in natural systems. Solvothermal processes imply the solvation, transport and recrystallization of elements in a gas phase. Results obtained from whole rock analysis from sanidinites from Laacher See (Germany) show a positive correlation between LOI, sulfate, Cl, and Na with the HFSE like Zr. Na-rich conditions seem to ameliorate the solvothermal transport of Zr. All these features point to the formation of sanidinites in the upper part of a magma chamber, where fluid consisting of SO3 and Cl compounds in addition to H2O, CO2 and HFSE (high field strength elements) like Zr accumulate.

  3. Liquidus temperature model for Hanford high-level waste glasses with high concentrations of zirconia

    International Nuclear Information System (INIS)

    A study was conducted on glasses based on a simulated transuranic waste with high concentrations of ZrO2 and Bi2O3 to determine the compositional dependence of primary crystalline phases and liquidus temperature (TL). Starting from a baseline composition, glasses were formulated by changing mass fractions of Al2O3, B2O3, Bi2O3, CeO2, Li2O, Na2O, P2O5, SiO2, and ZrO2, one at a time, while keeping the remaining components in the same relative proportions as in the baseline glass. Liquidus temperature was measured by heat treating glass samples for 24 h in a uniform temperature furnace. The primary crystalline phase in the baseline glass and the majority of the glasses was zircon (ZrSiO4). A change in the concentration of certain components (Al2O3, ZrO2, Li2O, B2O3, and SiO2) changed the primary phase to baddeleyite (ZrO2), while cerium oxide (CeO2) precipitated from glasses with more than 3 wt% CeO2. Zircon TL was strongly increased by Al2O3, ZrO2 and CeO2, and slightly by P2O5 and SiO2; decreased strongly by Li2O and Na2O and moderately by B2O3. A first-order model was constructed for TL as a function of composition for zircon primary crystalline phase glass

  4. Rb-Sr and Sm-Nd isotopic and REE studies of igneous components in the bulk matrix domain of Martian breccia Northwest Africa 7034

    Science.gov (United States)

    Nyquist, Laurence E.; Shih, Chi-Yu; McCubbin, Francis M.; Santos, Alison R.; Shearer, Charles K.; Peng, Zhan X.; Burger, Paul V.; Agee, Carl B.

    2016-03-01

    The bulk matrix domain of the Martian breccia NWA 7034 was examined petrographically and isotopically to better understand the provenance and age of the source material that make up the breccia. Both 147Sm-143Nd and 146Sm-142Nd age results for mineral separates from the bulk matrix portion of breccia NWA 7034 suggest that various lithological components in the breccia probably formed contemporaneously ~4.44 Ga ago. This old age is in excellent agreement with the upper intersection ages (4.35-4.45 Ga) for U-Pb discordia and also concordia defined by zircon and baddeleyite grains in matrix and igneous-textured clasts. Consequently, we confirm an ancient age for the igneous components that make up the NWA 7034 breccia. Substantial disturbance in the Rb-Sr system was detected, and no age significance could be gleaned from our Rb-Sr data. The disturbance to the Rb-Sr system may be due to a thermal event recorded by bulk-rock K-Ar ages of 1.56 Ga and U-Pb ages of phosphates at about 1.35-1.5 Ga, which suggest partial resetting from an unknown thermal event(s), possibly accompanying breccia formation. The NWA 7034 bulk rock is LREE enriched and similar to KREEP-rich lunar rocks, which indicates that the earliest Martian crust was geochemically enriched. This enrichment supports the idea that the crust is one of the enriched geochemical reservoirs on Mars that have been detected in studies of other Martian meteorites.

  5. 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

  6. Isotope geochemistry and fluid inclusion study of skarns from Vesuvius

    Science.gov (United States)

    Gilg, H.A.; Lima, A.; Somma, R.; Belkin, H.E.; de Vivo, B.; Ayuso, R.A.

    2001-01-01

    We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd isotope data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopite, F-bearing vesuvianite, wollastonite, gehlenite, meionite, forsterite, clinohumite, anorthite and Mg-poor calcite with accessory apatite, spinell, magnetite, perovskite, baddeleyite, and various REE-, U-, Th-, Zr- and Ti-rich minerals. Four major types of fluid inclusions were observed in wollastonite, vesuvianite, gehlenite, clinopyroxene and calcite: a) primary silicate melt inclusions (THOM = 1000-1050??C), b) CO2 ?? H2S-rich fluid inclusions (THOM = 20-31.3??C into the vapor phase), c) multiphase aqueous brine inclusions (THOM = 720-820??C) with mainly sylvite and halite daughter minerals, and d) complex chloride-carbonate-sulfate-fluoride-silicate-bearing saline-melt inclusions (THOM = 870-890??C). The last inclusion type shows evidence for immiscibility between several fluids (silicate melt - aqueous chloride-rich liquid - carbonate/sulfate melt?) during heating and cooling below 870??C. There is no evidence for fluid circulation below 700??C and participation of externally derived meteoric fluids in skarn formation. Skarns have considerably variable 206Pb/204Pb (19.047-19.202), 207Pb/204Pb (15.655-15.670), and 208Pb/204Pb (38.915-39.069) and relatively low 143Nd/144Nd (0.51211-0.51244) ratios. The carbon and oxygen isotope compositions of skarn calcites (??13CV-PDB = -5.4 to -1.1???; ??18OV-SMOW = 11.7 to 16.4???) indicate formation from a 18O- and 13C-enriched fluid. The isotope composition of skarns and the presence of silicate melt inclusion-bearing wollastonite nodules suggests assimilation of carbonate wall rocks by the alkaline magma at moderate depths (< 5

  7. 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.

  8. Bald Friar Metabasalt and Kennett Square Amphibolite: Two Iapetan Ocean Floor Basalts

    Science.gov (United States)

    Smith, R.C., II

    2006-01-01

    The Bald Friar Metabasalt (BFM) and Kennett Square Amphibolite (KSA) are basaltic units found in the Piedmont of southeastern Pennsylvania. The BFM is also recognized in northern Maryland. Both are believed to represent fragments of the floor of the Iapetus Ocean, but are not known occur in direct association with one another. The BFM typically occurs as small fragments having typical stratigraphic thicknesses of 2.5 m, and composed of greenish, fine-grained chlorite-epidote-actinolite-albite metabasalt in ophiolite me??lange. One bed of pillow basalt has been found at the type locality, Bald Friar, Cecil County, Maryland. Even though outcrops of BFM are highly discontinuous, they have a remarkable chemical uniformity over a strike length of 143 km and appear to be equivalent to the Caldwell Group 1b metabasalt of the Thetford, Quebec, area. The BFM is typically associated with ultramafic fragments and may be affiliated with the Baltimore Mafic Complex (BMC), from which a baddeleyite date of 442 +/- 7 Ma (Silurian) has been obtained. The BFM is probably a back arc basin basalt (BABB). Pod and schlieren chromite compositions suggest an island arc environment for the BMC itself. The poorly defined, informal "Conowingo Creek metabasalt" of Lancaster County, Pennsylvania, occurs on the north margin of the BMC and appears to be a fore arc boninite. The BFM and associated ultramafic fragments serve as a field-mappable marker for the structural equivalent of the Baie Verte-Brompton line in southeastern Pennsylvania and northern Maryland. Steatization of the associated ultramafic fragments has produced zones of extremely low competence that facilitated and localized thrusts of presumed Silurian age and later Alleghanian folding. The KSA typically occurs as much larger bodies having lengths of 3 km and composed of dark, medium-grained hornblende-plagioclase-clinopyroxene gneiss. No ultramafic rocks or me??lange have been recognized with the KSA. In Pennsylvania, the KSA

  9. The matrix effects in oxide-type U-bearing mineral LA-ICP-MS U-Pb isotopic dating and their correction methods%氧化物型含铀矿物LA-ICP-MS U-Pb年龄测定中的基体效应及其校正方法

    Institute of Scientific and Technical Information of China (English)

    崔玉荣; 周红英; 耿建珍; 李国占; 郝爽; 李惠民

    2015-01-01

    基体效应是矿物微区原位LA-ICP-MS U-Pb测年中备受关注的问题,因为其对测年结果准确性的影响不容忽视.通过介绍斜锆石、金红石、锡石、铌铁矿、晶质铀矿、沥青铀矿等氧化物型含铀矿物微区原位LA-ICP-MS U-Pb同位素测年过程中基体效应的影响和校正方法,简要评述其校正方法的优点、局限性,探索规律和相似性,解决寻找和研制稀有矿物标样的难题.对含铀矿物进行准确的微区原位LA-ICP-MS U-Pb同位素年龄测定,对于全面认识众多地质事件和矿床的生成演化历史,进而更准确地构建其年代构造格架、建立更合理的成岩成矿模式具有重要的科学意义.%The matrix effect is a problem of much concern in U-Pb isotopic dating by in situ LA-ICP-MS,and its influence on the accuracy of the dating results should not be ignored. The authors intend to study the influences and correction methods of matrix ef-fects on U-Pb isotopic dating by in-situ LA-ICP-MS for such minerals as baddeleyite, rutile, cassiterite, columbite, uraninite, pitch-blende and other oxide-type U-bearing minerals. This paper briefly describes the advantages and limitations of these correction methods in the hope of finding some regularity and similarity and solving difficult points in rare minerals standards preparation. In the accurate U-Pb isotopic dating by in situ LA-ICP-MS, the correction methods are of important scientific significance for further comprehensive understanding of the relevant geological generation and evolution history of the deposit, establishment of more accu-rate structural framework and creation of new petrogenic and metallogenic model.

  10. Petrological, geochemical and isotopic investigations on a carbonate-dyke and enclosed pyroxenite xenoliths from Val Mastallone (Ivrea-Verbano Zone): evidence of a cumulate carbonatite in the lower crust?

    Science.gov (United States)

    Galli, Andrea; Grassi, Daniele; Burg, Jean-Pierre; Schwab, Leo; Rickli, Jörg; Gianola, Omar

    2016-04-01

    The Ivrea-Verbano Zone (Italy/Switzerland) represents one of the best exposed mantle-crust sections worldwide. Its geological evolution has been governed by the Permian underplating of mantle-derived basic magmas („Mafic Complex") into the high-grade basement of the Southern Alps. In the Ivrea-Verbano Zone, marbles occur as concordant bodies or partly discordant carbonate-dykes. Generally, these dykes are constituted of calcite, diopside, scapolite, contain enclave of the host rocks and display sharp contacts to the host lithologies without evidences of alteration zones. In Val Mastallone, an up to 40 m thick carbonate-dyke with different characteristics occurs within mafic granulites. This dyke is composed of calcite, clinopyroxene and subordinate allanite and zircon. No scapolite is observed. The contacts to the host granulites are characterized by alteration zones composed of actinolite, chlorite, clinozoisite, plagioclase and calcite. The carbonate-dyke bears enclave of phlogopite-amphibole-apatite-rutile-ilmenite ± garnet or spinel clinopyroxenites. These rock type is not outcropping elsewhere in the proximity of the dyke, suggesting a significant transport. Host mafic granulite enclave are found exclusively at the margin of the dyke. Calcite dykelets rich in zircon, baddeleyite and other Ba, U, Th, REE-rich phases cut across the enclave. The carbonate-dyke shows an enrichment of LREE over HREE ((La/Yb)N = 14), with a Σ REE = 338 and Y/Ho = 27. On the chondrite-normalized REE abundances diagram, no Eu anomaly is observed. Mantle-normalized pattern shows strong negative anomalies at Cs, Rb, K, Pb, P, Zr, Hf, Ti and positive Ba, Th, Sr, Nd anomalies, similarly to the "world average carbonatites". Measured absolute trace element concentrations are lower than average carbonatites but significantly higher than typical limestones and similar to cumulate carbonatites found elsewhere in the world (e.g. India, China, Brazil). Grt-bearing clinopyroxenite enclave

  11. A new grand mean palaeomagnetic pole for the 1.11 Ga Umkondo large igneous province with implications for palaeogeography and the geomagnetic field

    Science.gov (United States)

    Swanson-Hysell, N. L.; Kilian, T. M.; Hanson, R. E.

    2015-12-01

    We present a new grand mean palaeomagnetic pole (Plong: 222.1°, Plat: -64.0°, A95: 2.6°, N = 49) for the ca. 1110 Ma Umkondo large igneous province (LIP) of the Kalahari Craton. New palaeomagnetic data from 24 sills in Botswana and compiled reprocessed existing data are used to develop a palaeomagnetic pole as the Fisher mean of cooling unit virtual geomagnetic poles (VGPs). The mean and its associated uncertainty provide the best-constrained pole yet developed for the province. Comparing data from individual cooling units allows for evaluation of palaeosecular variation at this time in the Mesoproterozoic. The elongation of the population of VGPs is consistent with that predicted by the TK03.GAD model lending support to the dipolar nature of the field in the late Mesoproterozoic. In our new compilation, 4 of 59 (˜7 per cent) of the igneous units have northerly declinations while the rest are south-directed indicating that a geomagnetic reversal occurred during magmatic activity. Interpreting which of these polarities corresponds with a normal or reversed geomagnetic field relative to other continents can constrain the relative orientations between cratons with time-equivalent data. This interpretation is particularly important in comparison to Laurentia as it bears on Kalahari's involvement and position in the supercontinent Rodinia. The dominance of south-directed declinations within the Umkondo Province was previously used to suggest that these directions are the same polarity as reversed directions from the early magmatic stage of the Keweenawan Midcontinent Rift of Laurentia. Two Umkondo sills with northerly declinations have U-Pb baddeleyite ages of ca. 1109 Ma that are temporally close to dated Midcontinent Rift units having reversed directions. Based on this comparison, and palaeomagnetic data from younger units in the Kalahari Craton, we favour the option in which the sites with northerly declinations from the Umkondo Province correspond to the

  12. 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

  13. Paleoproterozoic postcollisional magmatic belt of the southern Siberian craton

    Science.gov (United States)

    Salnikova, E. B.; Larin, A. M.; Kotov, A. B.; Levitsky, V. I.; Reznitsky, L. Z.; Kovach, V. P.; Yakovleva, S. Z.

    2003-04-01

    Paleoproterozoic time is characterized by large-scale collisional and postcollisional magmatic activity evidenced in the most of ancient cratons. This global event is related to the Arctic supercontinent assemblage (Rogers, 1996). The formation of postcollisional magmatic belt at 1.9-1.8 Ga within the south-west flanking of the Siberian craton is a remarkable example of these processes happened during overall lithospheric convergence. This belt is extends for about 3000 km from the southern Enisey ridge at the west to the central Aldan shield at the east. Within the central Aldan shield the latest collisional event occurred 1925+/-5 Ma (Kotov et al, 2003) and post-collisional subalkaline S- and I-type granites emplaced at 1916+/-10 Ma (Bibikova et al., 1989), 1901+/-1 Ma (Frost et al., 1998) and 1899+/-6 Ma (Kotov et al, 2003). However at the southern Olekma terrain (western Aldan shield) the syncollisional granites have formed at 1906+/-4 Ma and postcollisional Kodar granitoids were generated at 1876-1873 Ma (Larin et al., 2000). The is a tendency outlined in timing of postcollision processes to the west (in modern coordinates). Ages of postcollisional Kevakta granitoid plutons (1846+/-8 Ma) and volcanics of North-Baikal volcano-plutonic belt (1869+/-6 Ma 1856+/-3 Ma), Baikal folded area, support this tendency. Emplacement of the Primorsky complex postcollisional rapakivi-type granitoids (southern Baikal lake) occurred at 1859+/-16 Ma (Donskaya et al., 2002). New results of U-Pb single zircon and baddeleyite dating demonstrate that formation of late-synkinematic syenite, charnockite and pegmatitic veins (1856±12 Ma, 1853±20 Ma) and calciphyre (1868±2 Ma) within the eastern part of the Sharyzhalgay block (southern Baikal lake) occurred virtually within the same episode. Postcollisional intrusive charnockite of the Shumikha complex from the western Sharyzhalgay block dated at 1861±1 Ma (Donskaya et al., 2001) and 1871±17 Ma (Levitsky et al., 2002). Subalcaline

  14. The further age constraint of Hualong Rock Group in the eastern segment of South Qilian Mountains%南祁连东段化隆岩群形成时代的进一步限定

    Institute of Scientific and Technical Information of China (English)

    何世平; 李荣社; 王超; 于浦生; 张宏飞; 辜平阳; 时超

    2011-01-01

    The Hualong Rock Group of South Qilian orogenic basement remnants has aroused much interest among geologists for the occurrence of basic-ultrabasic rocks closely related to Cu-Ni (-PGE) ore deposits.With the acquisition of some precise Neoproterozoic zircon isotopic age data, the traditional understanding that Hualong Rock Group was formed in Archean-Paleoproterozoic has been challenged.High resolution LA-ICP-MS zircon U-Pb in situ dating of banded two mica-plagiogneiss (para-metamorphic rocks) from Hualong Rock Group in Riyue village of southern Huangyuan County yielded an age of 891 ± 7 Ma, which represents the lower age boundary of Hualong Rock Group.The age recently obtained from banded biotite-plagioclase amphibolite (whose protolith was intermediate volcanic rocks) is 884 ± 9 Ma.Based on isotopic dating combined with the results obtained by previous researchers, the authors further restricted the age of Hualong rock Group to Early Neoproterozoic, i.e., Qingbaikou period.It is believed that the volcano-sedimentary rocks of Hualong Rock Group serve as geological records of the breakup of the Rodinia supercontinent.Recently, zircon U-Pb dating yielded an age of 724.4 ± 3.7 Ma from gneissic plagioclase amphibolite (whose protolith was gabbro)near the Dadaoerji Cu-Ni ore deposit in the western part of the Qilian orogenic belt, whereas a U-Pb age of 724.4 ± 3.7 Ma was yielded from zircon and baddeleyite in Jinchuan ultrabasic rock of Longshou Mountain area in northern Qilian orogenic belt; these data can also be regarded as geological records of the breakup of the Rodinia supercontinent.These results indicate that the importance of Rodinia supercontinent breakup event and its related mineralization in Precambrian period of the Qilian orogenic belt and its adjacent areas should not be underestimated.%作为南祁连造山带基底残块的化隆岩群,由于产出有与Cu-Ni(-PGE)矿紧密相关的基性-超基性岩而倍受关注.随着一些新元古代精

  15. Re Os isotopic systematics of the Voisey's Bay Ni Cu Co magmatic ore system, Labrador, Canada

    Science.gov (United States)

    Lambert, D. D.; Foster, J. G.; Frick, L. R.; Li, C.; Naldrett, A. J.

    1999-06-01

    Re and Os concentrations and Os isotopic compositions have been obtained for massive, matrix, and disseminated sulphide ores from three environments within the Voisey's Bay intrusion (the `Ovoid', Eastern Deeps, and Discovery Hill Zone) in order to assess the role of crustal contamination in the genesis of this large Cu-Ni-Co deposit. These samples have high Re concentrations (148 to 288 ppb, in 100% sulphide) for their common Os concentrations (4.8 to 24 ppb, in 100% sulphide), yielding high Re/Os ratios (12 to 33). These data confirm that the magma parental to the Voisey's Bay ore system was broadly basaltic in major element chemistry rather than picritic, consistent with the low Ni/Cu ratio of the ores (˜1.5). Re-Os isotopic data exhibit a limited spread in 187Re/ 188Os (57 to 157) and define an imprecise 1323±135 Ma `model 3' isochron, likely the result of small R-factor variations within the ore system. The Re-Os isochron age is within error of 1334 Ma U-Pb ages obtained for baddeleyite from the ore-bearing troctolites, demonstrating that whole rock Re-Os isotopic systematics have remained closed since crystallisation. The initial Os isotopic composition of the isochron ( γOs=1040±200) implies significant magma interactions with radiogenic Os that most likely resides in the Nain-Churchill Province crust. These data are, therefore, consistent with the parental magma achieving sulphide saturation as a result of contamination by radiogenic crustal components, with further addition of base and precious metals as a function of R-factor. Analyses of sulphide separates from the Proterozoic Tasiuyak (Churchill) and Archaean Nain gneisses confirm that both units contained significant Os (8.6 ppb and 0.38 ppb, respectively) that was very radiogenic at 1334 Ma ( γOs=1908 and 5202, respectively), yielding crustal residence TCHUR model ages of 2200 to 2400 Ma. However, these model ages may have been affected by Re and/or Os mobility during the 1.85 Ga Torngat and 1

  16. Emeishan volcanism and the end-Guadalupian extinction: New U-Pb TIMS ages

    Science.gov (United States)

    Mundil, Roland; Denyszyn, Steve; He, Bin; Metcalfe, Ian; Yigang, Xu

    2010-05-01

    from numerous sedimentary archives. A further complication arises from the severe tectonic (and resulting thermal) overprint, due to the closure of the Tethys and the collision of the Indian plate with Asia, of most of the area where Emeishan volcanic products are exposed. Also, currently existing paleo-environmental data are scarce and insufficient for testing this hypothesis with confidence, because studies using stable isotopes as proxies are restricted to short profiles from only a few sites. Therefore, fundamental questions remain unanswered. We present new data U-Pb IDTIMS ages with permil-level resolution that constrain the timing of Emeishan volcanism and the timing of biotic events recorded in sediments. In detail, U-Pb results are from felsic intercalations within late stage Emeishan products and biostratigaphically calibrated marine sedimentary sections in southwestern and central China as well as thick tuffs within terrestrial sections from the Bowen Basin in eastern Australia. There is also great potential for obtaining precise U-Pb age results on volcanic products with basaltic composition using the accessory mineral baddeleyite the occurrence of which we have already confirmed. Geochronological and geochemical research is complemented with paleo-enviromental studies and biostratigraphy. We expect that through integration of U-Pb and 40Ar/39Ar geochronology with chemo- and biostratigraphy, the time scale of the Middle through Late Permian will be greatly improved and will lead to a more realistic evaluation of potential causes for the biotic crisis and its aftermath.

  17. 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