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1

Fractionation in the solar nebula - Condensation of yttrium and the rare earth elements  

Microsoft Academic Search

The condensation of Y and the rare earth elements (REE) from the solar nebula may be controlled by thermodynamic equilibrium between gas and condensed solids. Highly fractionated REE patterns may result if condensates are removed from the gas before condensation is complete. It is found that the fractionation is not a smooth function of REE ionic radius but varies in

W. V. Boynton

1975-01-01

2

Microprobe analyses of rare earth element fractionation in meteoritic minerals  

Microsoft Academic Search

Two meteorites were analyzed by PIXE with the Los Alamos nuclear microprobe. The enstatite achondrite Pen~a Blanca Spring and the ordinary chondrite St Severin were chosen as likely candidates for use in 244Pu (t1\\/2 = 82 my) cosmochronology and geochronology. These applications require the meteoritic minerals to have unfractionated actinides and lanthanides relative to ``cosmic'' elemental abundance ratios. The PIXE

T. M. Benjamin; C. J. Duffy; C. J. Maggiore; P. S. Z. Rogers; D. S. Woolum; D. S. Burnett; M. T. Murrell

1984-01-01

3

Efficient mobilization and fractionation of rare-earth elements by aqueous fluids upon slab dehydration  

NASA Astrophysics Data System (ADS)

The characteristic REE fractionation pattern in arc magmas compared to MOR-basalts results from the selective mobilization of light rare-earth elements (LREE) by slab-derived mobile components. However, the nature and composition of the slab flux, and the actual mechanisms responsible for the transfer of rare-earth elements (REE) from the slab to the mantle wedge remain unclear. We present experimental data on the solubility of selected REE in ligand-bearing aqueous fluids and a hydrous haplogranitic melt at 2.6 GPa and 600-800 °C, spanning the conditions relevant to slab dehydration and melting. The solubilities of REE in aqueous fluids increase more than an order of magnitude with temperature increasing from 600 to 800 °C. Addition of ligands such as Cl-, F-, CO32-, SO42- in relatively small concentrations (0.3-1.5 m [mol/kg H2O]) has a pronounced effect further enhancing REE solubilities. Each ligand yields a characteristic REE pattern by preferential dissolution of either the light or the heavy REE. For example, the addition of NaCl to the aqueous fluids yields highly elevated LREE/HREE ratios (La/Yb=17.4±4.3), whereas the addition of fluoride and sulfate ligands significantly increases the solubility of all REE with moderate LREE/HREE fractionation (La/Yb?4). The addition of Na2CO3 results in preferential increase of HREE solubilities, and yields La/Yb ratio of 1.6±0.5 by flattening the moderately fractionated REE pattern seen in pure aqueous fluids. The solubilities in hydrous haplogranite melt are moderate in comparison to those observed in aqueous fluids and do not lead to pronounced REE fractionation. Therefore, REE can be effectively mobilized and fractionated by aqueous fluids, compared to felsic hydrous melts. Furthermore, the aqueous fluid chemistry has a major role in determining REE mobilities and fractionation upon slab dehydration in addition to the significant control exerted by temperature. Our results show that chloride-bearing slab-derived aqueous fluids have a significant contribution to the formation of REE-signatures in arc-magmas, especially at lower slab surface temperatures.

Tsay, A.; Zajacz, Z.; Sanchez-Valle, C.

2014-07-01

4

Ocean particle chemistry: The fractionation of rare earth elements between suspended particles and seawater  

SciTech Connect

Sargasso Sea suspended particles were sequentially digested with three chemical treatments (acetic acid, mild HCl/HNO[sub 3], and HF/HNO[sub 3]/HCl in a bomb). The latter two treatments dissolve detrital minerals, while the acetic acid removes surface coatings (organic matter and Mn oxides). The rare earth element (REE) composition of the surface coatings, in marked contrast to the crust-like REE composition of the two detrital phases, is extensively fractionated with respect to both filtered seawater and the crust. Surface coatings are responsible for the removal and fractionation of REEs from seawater and, as such, play a key role in the marine geochemical cycles of trace elements. Relative to seawater, the surface coatings are systematically enriched tenfold across the trivalent REEs from Lu to La and develop large positive Ce-anomalies. The Ce-anomalies of the coatings switch from being negative (seawater-like) in the upper 100 m to being strongly positive at greater depths. The ingrowth of Ce and LREEs on particle surfaces reflects the in situ oxidation of dissolved Ce(III) to particulate Ce(IV), and the preferential removal of LREE(III)s over HREE(III)s. REEs(III) fractionation of this type is consistent with particle/solution models. Both processes appear to be related to the in situ formation of Mn oxide particles from the oxidation of dissolved Mn(II) in the upper 200 m of the water column. Preferential removal of LREEs in the upper waters is countered by their preferential release at depth due to remineralization of surface coatings on particles. A new method is explored for estimating the residence time of suspended particles by combining Ce concentration data of dissolved and surface-bound phases with the Ce(III) oxidation rate measurements of MOFFETT (1990). A Ce-based residence time of thirteen days is similar in magnitude to the value calculated from U-[sup 234]Th disequilibria in the Sargasso Sea.

Sholkovitz, E.R. (Woods Hole Oceanographic Institution, Woods Hole, MA (United States)); Landing, W.M.; Lewis, B.L. (Florida State Univ., Tallahassee, FL (United States))

1994-03-01

5

Microprobe analyses of rare-earth-element fractionation in meteoritic minerals  

SciTech Connect

Two meteorites were analyzed by PIXE with the Los Alamos Nuclear Microprobe. The enstatite achondrite Pena Blanca Spring and the ordinary chondrite St. Severin were chosen as likely candidates for use in /sup 244/Pu (t/sub 1/2/ = 82 my) cosmochronology and geochronology. These applications require the meteoritic minerals to have unfractionated actinides and lanthanides relative to cosmic elemental abundance ratios. The PIXE analyses produced evidence of actinide-lanthanide fractionation in Pena Blanca Spring oldhamite (CaS) whereas the St Severin phosphates, whitlockite and chlorapatite, do not exhibit this fractionation.

Benjamin, T.M.; Duffy, C.J.; Rogers, P.S.Z.; Maggiore, C.J.; Woolum, D.S.; Burnett, D.S.; Murrell, M.T.

1983-01-01

6

Fractionation of Rare Earth Elements during Soil Formation along Feather River Basin Hillslopes in the California Sierra Nevada  

NASA Astrophysics Data System (ADS)

The mobility of rare earth elements (REE) has been debated by scientists for years. This study presents soil and soil moisture data from an ongoing study that examines how REEs fractionate as rock weathers into soil. The Middle Fork Feather River in Northern California, the location of the study site, takes advantage of an erosional signal propagating through the basin and compares traditional methods of REE normalization then contrasts them with elemental losses based on mass balance calculations (tau). Analyzed by ICP-MS using the whole-rock Li-borate dissolution method, soil and water sample collection took place along two differentially eroding hill slopes (a shallow slope above the knick-point and a more inclined slope below the knick-point). Using Zr as an immobile element, the mass-balance method clearly portrays REE fractionation occurring within the soils, whereas traditional REE normalization patterns do not clearly display fractionation relative to the parent material. While REEs fractionate approximately to the same extent in the topmost soils of both hill slopes, the more actively eroding hill slope fractionates REEs faster because of a faster rate of soil chemical weathering. While the full meaning of this work is still underway, current progress indicates that significant REE fractionation occurs during chemical weathering, implying that using REEs as tracers for surfaces processes requires significant care.

Steinert, T.; Weinman, B.; Yoo, K.; Mudd, S. M.; Kouba, C. M.; Maher, K.

2013-12-01

7

Microprobe analyses of rare-earth-element fractionation in meteoritic minerals  

Microsoft Academic Search

Two meteorites were analyzed by PIXE with the Los Alamos Nuclear chondrite St. Severin were chosen as likely candidates for use in Pub244 (t1\\/2\\/ = 82 my) cosmochronology and geochronology. These applications require the meteoritic minerals to have unfractionated actinides and lanthanides relative to cosmic elemental abundance ratios. The PIXE analyses produced evidence of actinide-lanthanide fractionation in Pena Blanca Spring

T. M. Benjamin; C. J. Duffy; P. S. Z. Rogers; C. J. Maggiore; D. S. Woolum; D. S. Burnett; M. T. Murrell

1983-01-01

8

Siderophile Element Fractionation in the Earth's Core: Direct Estimate of Partition Coefficients from Primitive Siberian Flood Basalts  

NASA Astrophysics Data System (ADS)

Evidence from Os isotopes suggests that the siderophile element signature in some deep-mantle plumes may be derived from the outer core. The siderophile element pattern in the least fractionated plume basalts therefore may reflect solid-liquid metal fractionation, rather than that from partial melting of the upper mantle. Partition coefficients (D) derived from IIAB irons are governed by three major factors; element melting point, atomic radius and electron configuration. Values for Au, Ni, Re and the heavy platinum group elements (HPGE) plotted against melting point lie on a hyperbola with Os at the maximum. The light PGE (LPGE) also show a trend of increasing D with melting point but lie below the HPGE trend, perhaps due to differences in free atom electronic configuration. Siberian Flood Basalts (SFB) are of plume origin, and the Mokulaevsky and Morongovsky flows are the least crustally contaminated. Abundances of Ni, Rh, Pd, Ir, Pt and Au in these flows plot on a smooth curve against melting point when chondrite-normalized, but not when mantle-normalized. Thus, we explore the possibility that the SFB distributions reflect fractionation in the core rather than in the upper mantle. For 5.5 per cent crystallization, iron meteorite data yield much less fractionation of Ir than is seen in SFB, suggesting that D for Ir in the Earth's core is larger. Inversion of the SFB data yields a smooth curve when D values of PGE, Au and Ni are plotted against melting point. The D value for Ir is estimated to be about 5 times larger than in iron meteorites. If values for Re and Os are similarly enhanced, as suggested by high pressure experiments, Os isotopes in plumes may be more compatible with gradual formation of the inner core rather than early growth to the present size.

Morgan, J. W.; Walker, R. J.

2001-12-01

9

Rare earth elements in intertidal sediments of Bohai Bay, China: Concentration, fractionation and the influence of sediment texture.  

PubMed

Surface sediments from intertidal Bohai Bay were assessed using a four-step sequential extraction procedure to determine their concentrations of rare earth elements (REEs) and the chemical forms in which those elements were present. The normalized ratios La/Gd and La/Yb showed that LREE contents were not significantly higher than the middle REEs or HREE contents. A negative Ce anomaly and positive Eu were observed in sand and silty sand sediments, whereas no significant Ce or Eu anomaly was found in clayey silt sediments. Residual fraction of REEs accounted for the majority of their total concentrations. Middle REEs were more easily leached than other REEs, especially in clayey silt sediment. REEs contents in the surface sediment from the intertidal Bohai Sea were consistent with data from the upper continental crust and China shallow sea sediments, indicating that they were generally unaffected by heavily anthropogenic effects from adjacent areas. PMID:24793516

Zhang, Yong; Gao, Xuelu; Arthur Chen, Chen-Tung

2014-07-01

10

Accumulation and fractionation of rare earth elements in atmospheric particulates around a mine tailing in Baotou, China  

NASA Astrophysics Data System (ADS)

Rare earth elements (REEs) have been increasingly emitted into the atmosphere with a worldwide increase in use of these metals. However, the research on REEs in atmospheric particulates is fairly limited. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 ?m (PM10) were collected around a rare earth mine tailing in Baotou, the largest rare earth industrial base in China, in August 2012 and March 2013, for the analyses of REE levels and distributions. The total concentrations of REEs for TSP were 172.91 and 297.49 ng/m3, and those for PM10 were 63.23 and 105.52 ng/m3, in August 2012 and March 2013, respectively. Enrichment factors for all 14 analyzed REEs in the TSP and PM10 indicated that the REE enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in spring season. The spatial distribution of REEs in TSP showed a strong gradient in the prevailing wind direction. The chondrite-normalized patterns of REEs in TSP and PM10 were similar with the conspicuous fractionation between light REEs and heavy REEs.

Wang, Lingqing; Liang, Tao

2014-05-01

11

Fraction characteristics of rare earth elements in the surface sediment of Bohai Bay, North China.  

PubMed

Surface sediment samples were collected at 27 stations of Bohai Bay, North China. Sequential extractions were carried out in this study. REE were leached out from four labile fractions: Exchangeable (L1), bound to carbonates (L2), bound to Fe-Mn oxides (L3), bound to organic matter (L4), and the remainder was residual (R5). The total contents of REE fluctuate slightly in Bohai Bay, and are mainly concentrated in the middle region, showing relatively higher levels in the north than that in the south of Bohai Bay. Percentages of L1, L2, L3, L4, and R5 for REE suggest that the residual fraction accounts for the major component of REE, whereas Fe-Mn oxides also play important roles in combining labile REE. As the REE complex is not stabilized, the competition of complex could induce dissociation of the complex and redistribution of the REE in various environments. According to REE patterns and Y/Ho ratios of samples, REE are not anthropogenic or oceanic sources but riverine input, whereas suitable environment varieties can slightly affect the patterns and fractionations of REE. As powerful tracers for the variable of environment, higher anomaly of Eu and Ce in southern regions indicates a greater reduction in the condition of surface sediment in the south than that in the north of Bohai Bay. PMID:22270586

Xu, Yayan; Song, Jinming; Duan, Liqin; Li, Xuegang; Yuan, Huamao; Li, Ning; Zhang, Peng; Zhang, Ying; Xu, Sisi; Zhang, Mo; Wu, Xiaodan; Yin, Xuebo

2012-12-01

12

Analysis of some Earth, Moon and Mars samples in terms of gamma ray energy absorption buildup factors: Penetration depth, weight fraction of constituent elements and photon energy dependence  

Microsoft Academic Search

The Earth, Moon and Mars samples have been investigated in terms of gamma ray energy absorption buildup factors (EABF) depending on penetration depth, weight fraction of constituent elements and photon energy. The five parameter geometric progression (G-P) fitting approximation has been used to compute the buildup factors in the energy region 0.015–15MeV up to a penetration depth of 40 mean

Murat Kurudirek; Bekir Dogan; Yüksel Özdemir; Anderson Camargo Moreira; Carlos Roberto Appoloni

2011-01-01

13

Uptake and fractionation of rare earth elements on hydrothermal plume particles at 9°45'N, East Pacific Rise  

NASA Astrophysics Data System (ADS)

Particulate samples (>0.45 ?m) from a neutrally buoyant hydrothermal plume at 9°45'N on the northern East Pacific Rise were collected using large volume in situ filtration and analyzed for Fe, Al, Mn, Ni, and fourteen rare earth elements (REE). The Sm/Fe ratio (a proxy for overall REE/Fe) and Nd/Er (light/heavy REE fractionation) increased moderately with decreasing particulate Fe. Chemically, the sense of these relationships matched that documented previously in the TAG plume on the Mid-Atlantic Ridge (German et al., 1990), although particulate Fe was about 10 fold lower at 9°45'N. Spatial trends relative to the vent source, however, were opposite of expectation because slow Fe(II) oxidation and Fe(III) colloid aggregation over this interval led to increased particulate Fe (10-26 nM) with distance from source (Field and Sherrell, submitted). After subtraction of non-plume background particle composition, plume particles at 9°45'N and TAG had indistinguishable ranges of light REE-enriched fractionation relative to ambient seawater and had very similar Sm/Fe (therefore Kd for Fe oxyhydroxides), demonstrating that plume particles in both oceans reflect to a first degree the local seawater REE composition. Within-plume REE variations at 9°45'N were investigated using a simple mixing model which accounts for the bulk Fe-Al-Mn variations in the plume using two endmembers: fresh hydrothermal oxyhydroxide precipitates and ridge-crest background particles (composed largely of locally resuspended sediment). Sm/Fe and Nd/Er plot linearly with mixing ratio (R > 0.96), implying that the observed REE trends result from mixing of these two endmembers. Extrapolation to the composition of pure hydrothermal precipitates suggests that Nd/Er is fractionated relative to seawater by a factor of 1.8 during adsorption onto fresh Fe oxyhydroxide particles. The ridge-crest background particles are 5 fold higher in Sm/Fe and Nd/Er is 2.49 relative to seawater, partly a result of enriched terrigenous component in the resuspended matter. A reinterpretation of REE at TAG reveals that positive curvature in REE vs. Fe plots, argued previously to reflect continuous REE uptake (i.e., increasing Kd; German et al., 1990), may result from local depletion of the dissolved REE pool by partitioning onto Fe particles at Fe > 100 nM. Similar drawdown effects could contribute to the variable degrees of curvature observed for all seawater-source particle-reactive species in plumes that are sampled at high particulate Fe concentration. In sum, REE behavior in hydrothermal plumes is more consistent with equilibrium adsorption and mixing of distinct particle types, than with kinetic uptake control. Precise measurements of REEs in modern ridge-crest metalliferous sediments could be compared to the endmember composition calculated from the plume data to evaluate long-term changes in REE of the hydrothermal component.

Sherrell, Robert M.; Field, M. Paul; Ravizza, Greg

1999-06-01

14

Rare earth element fractionation during the precipitation and crystallisation of hydrous ferric oxides from anoxic lake water  

Microsoft Academic Search

An enrichment of light rare earth elements (LREE) is characteristic for most of the acidic, Fe- and SO4-rich pit lakes and groundwaters in the lignite mining area of Lower Lusatia (Germany). One of these acidic lakes – the pit lake “RL 1223” – has a strong thermal and chemical stratification. The upper water layer (0–9m) shows pH values of about

Elke Bozau; Jörg Göttlicher; Hans-Joachim Stärk

2008-01-01

15

Condensation and fractionation of rare earths in the solar nebula  

Microsoft Academic Search

The condensation behavior of the rare earth elements in the solar nebula is calculated on the basis of the most recent thermodynamic data in order to construct a model explaining group II rare earth element patterns in Allende inclusions. Models considered all involve the removal of large fractions of the more refractory heavy rare earth elements in an early condensate,

A. M. Davis; L. Grossman

1979-01-01

16

Analysis of some Earth, Moon and Mars samples in terms of gamma ray energy absorption buildup factors: Penetration depth, weight fraction of constituent elements and photon energy dependence  

NASA Astrophysics Data System (ADS)

The Earth, Moon and Mars samples have been investigated in terms of gamma ray energy absorption buildup factors (EABF) depending on penetration depth, weight fraction of constituent elements and photon energy. The five parameter geometric progression (G-P) fitting approximation has been used to compute the buildup factors in the energy region 0.015-15 MeV up to a penetration depth of 40 mean free paths (mfp). The maximum values of EABF have been observed for the Earth, Mars and Moon samples at 0.2, 0.3 and 0.2 MeV, respectively. At the corresponding energies where maximum EABF occur, the Earth samples have the highest and the Mars samples have the lowest EABF values. There is no significant variation in EABF for the Earth, Moon and Mars samples beyond 1 MeV, hence the values of EABF remain constant with the variation in chemical composition for all the given materials. Finally, the buildup factors so obtained have been discussed in function of the penetration depth, weight fraction of constituent elements and photon energy.

Kurudirek, Murat; Dogan, Bekir; Özdemir, Yüksel; Moreira, Anderson Camargo; Appoloni, Carlos Roberto

2011-03-01

17

Effects of organic ligands on fractionation of rare earth elements (REEs) in hydroponic plants: an application to the determination of binding capacities by humic acid for modeling.  

PubMed

Previous studies have revealed the fractionation processes of rare earth elements (REEs) in hydroponic plants, with a heavy REE (HREE, the elements from Gd to Lu) enrichment in leaves. In this study, effects on the HREE enrichment in soybean leaves with additions of carboxylic acids (acetate, malate, citrate, NTA, EDTA and DTPA) and two soil humic acids (HAs) were investigated. REE speciation in carboxylic acid and HA solutions was simulated using Visual MINTEQ and Model V, respectively. The results showed that the effects caused by carboxylic acids were strongly dependent on the differences between their binding strengths for light REEs (LREEs, the elements from La to Eu) and those for HREEs. A good correlation existed between these effects and the changes of free REE ions in solutions. This relationship was also observed for the HA treatments, provided that the intrinsic equilibrium constants of REEs for cation-proton exchange with HA (i.e., pK(MHA)) in Model V were estimated using a free-energy relationship with the stability constants for REE complexation with lactic acid. It is suggested that this set of pK(MHA) values is more suitable for use in Model V for the simulation of REE complexation with HA. PMID:16930675

Ding, ShiMing; Liang, Tao; Zhang, ChaoSheng; Yan, JunCai; Zhang, ZiLi

2006-12-01

18

Condensation and fractionation of rare earths in the solar nebula  

NASA Technical Reports Server (NTRS)

The condensation behavior of the rare earth elements in the solar nebula is calculated on the basis of the most recent thermodynamic data in order to construct a model explaining group II rare earth element patterns in Allende inclusions. Models considered all involve the removal of large fractions of the more refractory heavy rare earth elements in an early condensate, followed by the condensation of the remainder at a lower temperature. It is shown that the model of Boynton (1975) in which one rare earth element component is dissolved nonideally in perovskite according to relative activity coefficients can not reasonably be made to fit the observed group II patterns. A model in which two rare earth components control the patterns and dissolve ideally in perovskite is proposed and shown to be able to account for the 20 patterns by variations of the perovskite removal temperature and the relative proportions of the two components.

Davis, A. M.; Grossman, L.

1979-01-01

19

Are C1 chondrites chemically fractionated - A trace element study  

NASA Technical Reports Server (NTRS)

Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for a large variety of elements, including rare earths. The sample processing is described, including the irradiation, chemical procedure, rare earths separation, counting techniques, radiochemical purity check, and chemical yields. The results of consistency checks on a number of elements are discussed. Abundances for siderophiles, volatiles, and rare earths are presented and discussed. Tests are presented for fractionation of rare earths and other refractories, compositional uniformity of C1's, and interelement correlations. There is no conclusive evidence for nebular fractionation affecting C1's. Three fractionation-prone rare earths have essentially the same relative abundances in C1's and all other chondrite classes, and hence are apparently not fractionated in C1's.

Ebihara, M.; Wolf, R.; Anders, E.

1982-01-01

20

Binding and transport of rare earth elements by organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS  

NASA Astrophysics Data System (ADS)

Water samples were collected from six small rivers in the Yukon River basin in central Alaska to examine the role of nanocolloids (0.5-40 nm) in the dynamics and transport of rare earth elements (REEs) in northern high latitude watersheds influenced by permafrost. Total dissolved (<0.45 ?m) concentrations and the 'nanocolloidal size distributions' (0.5-40 nm) of UV-absorbing dissolved organic matter, Fe, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu were determined by on-line coupling of flow field-flow fractionation (FFF) with a UV-absorbance detector and ICP-MS. Total dissolved and nanocolloidal concentrations of the REEs co-varied with dissolved organic carbon (DOC) in all rivers and between spring flood and late summer baseflow. The nanocolloidal size distributions indicated the presence of three major components of nanocolloids: the 0.5-3 nm 'fulvic-rich nanocolloids' occurring throughout the sampling season, the 'organic/iron-rich nanocolloids' residing in the <8 nm size range during the spring flood, and the 4-40 nm iron-rich nanocolloids occurring during summer baseflow. REEs associated with all the three components of nanocolloids, but the proportions associated with the fulvic-rich nanocolloids during summer baseflow increased with increasing REE molar mass, which is consistent with the increase in stability of organic REE-complexes with increasing REE molar mass. Normalization of the measured REE-concentrations with the average REE-concentrations of the upper continental crust revealed a dynamic change in the physicochemical fractionation of REEs. During the spring flood, REE-binding in all the rivers was dominated by the <8 nm organic/iron-rich nanocolloids, likely being eroded from the upper organic-rich soil horizon by the strong surface runoff of snowmelt water. During the summer, the REE-binding in rivers with large groundwater input was dominated by small (<0.5 nm) organic and/or inorganic complexes, while lower proportions of the REEs were associated with both the 0.5-3 nm fulvic rich and 4-40 nm iron rich nanocolloids and with larger >40 nm colloids. In a river sampled at higher altitude, the <8 nm organic/iron-rich and 4-40 nm iron-rich nanocolloids dominated the REE-binding also during the summer, which could be a result of persistent permafrost confining water flows to the upper organic-rich soil horizons.

Stolpe, Björn; Guo, Laodong; Shiller, Alan M.

2013-04-01

21

Magnetite fractionation of "chalcophile" elements  

NASA Astrophysics Data System (ADS)

Submarine-quenched glasses provide the clearest record of magmatic evolution available, especially with respect to potentially volatile elements and compounds. A comprehensive suite of arc- and backarc glasses recovered during several research voyages in the SW Pacific are being analysed by a number of research teams in an effort to document genesis and fractionation processes involved in the evolution of subduction- related magma systems. As part of these studies, a suite of basalt to dacite composition glasses recovered from the arc-like Pacmanus Site in the Manus Backarc Basin have been examined in detail. Sun et al. (2004) found trends of increasing enrichments of Re, Cu, and Au with SiO2 in the range from 50 to 60 wt% SiO2. From this stage of magmatic evolution, marked depletions in all these elements are observed in glasses of higher SiO2 contents. The reasons for this trend have been unclear, although a mechanism involving the cessation of olivine and initiation of magnetite saturation was proposed by Sun et al. Our analysis of a larger suite of glasses from the Manus Basin has now confirmed these trends, and found the same behaviour for Zn and Mn. Similarly, analysis of a suite of basalt to dacite glasses recovered from the arc-like Valu Fa Ridge in the Lau Backarc Basin has produced trends for these elements very similar to those of the Pacmanus location. LA-ICP-MS analysis of microphenocrysts in these glasses has shown that magnetite is highly enriched in Re relative to the coexisting melt (Kd up to 7.8 for Re). Magnetite/melt partition coefficients for Re, Mn and Yb can be used to precisely model the liquid line of descent during magnetite (plus clinopyroxene and plagioclase) fractionation using Re vs. Mn/Yb. The variation of Pt abundances with SiO2 for both these suites contrasts with other nominally chalcophile trace elements in showing rapid early depletion from the most Mg-rich basalt through to more SiO2-rich compositions, with no maximum at 60 wt% SiO2. Silver on the other hand is essentially constant at 0.02 to 0.05ppm throughout the basalt to dacite compositional range. Several other compositional features of the Pacmanus and Valu Fa suites are also noteworthy. For example while S has an abundance maximum at 60wt% SiO2 (similar to Fe and Re), and then diminishes in concentration in more silica-rich magmas, Se is initially depleted at 60wt% SiO2 but then increases in abundance as SiO2 increases further. We suggest these features result from sulfide saturation coincidentally with (or shortly after) magnetite saturation. While Se is initially partitioned into the immiscible sulfide phase, moderate incompatibility remains between the overall fractionating assemblage of plagioclase-pyroxene- magnetite and minor sulfide. Pt on the other hand is likely being removed as a native element/alloy. Sun, W, Arculus, RJ, Kamenetsky, VS and Binns, RA, 2004, Release of gold-bearing fluids in convergent margin magmas prompted by magnetite crystallisation. Nature, v. 431, p. 975-978.

Mavrogenes, J. A.; Jenner, F. E.; Arculus, R. J.

2008-12-01

22

Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups  

NASA Astrophysics Data System (ADS)

This study presents a general model for the evaluation of Rayleigh fractional crystallisation as the principal differentiation mechanism in the formation of regionally zoned common and rare-element pegmatites. The magmatic evolution of these systems from a granitic source is reconstructed by means of alkali element and rare earth element (REE) analyses of rock-forming minerals (feldspars, micas and tourmaline), which represent a whole sequence of regional pegmatite zonation. The Gatumba pegmatite field (Rwanda, Central Africa) is chosen as case study area because of its well-developed regional zonation sequence. The pegmatites are spatially and temporally related to peraluminous G4-granites (986 ± 10 Ma). The regional zonation is developed around a G4-granite and the proximal pegmatites grade outwardly into biotite, two-mica and muscovite pegmatites. Rare-element (Nb-Ta-Sn) pegmatites occur most distal from the granite.

Hulsbosch, Niels; Hertogen, Jan; Dewaele, Stijn; André, Luc; Muchez, Philippe

2014-05-01

23

Major Element Fractionation During Differentiation  

NSDL National Science Digital Library

This problem set introduces some of the more advanced uses of Excel to not only calculate how the chemistry of a magma changes with crystallization but also to see how the liquidus assemblage can drastically change the evolution of the remaining magma. Once they have their calculations complete, students plot the results and answer questions on the geochemical trends observed through the crystallization sequence. This problem set reinforces quantitative problem solving skills using a spreadsheet and has the students think about mineralogical controls on magma evolution. This exercise is modified from one that Clark Johnson assigned at University of Wisconsin. I find this exercise to be more instructive for some of the tricks and tools in Excel, but there are some interesting questions that can derive from it. This assignment is often the first time the light goes on that you can end up with different composition magmas depending on what minerals are crystallizing, and that depends on the pressure of crystallization. There are many more questions that could be asked, such as where does this model fall short? What could be added or considered to make this a more realistic simulation of fractionation (more trace elements or REE).

24

Rare earth elements in synthetic zircon. 1. synthesis, and rare earth element and phosphorus doping  

Microsoft Academic Search

Sedimentary mineral assemblages commonly contain detrital zircon crystals as part of the heavy-mineral fraction. Age spectra determined by U-Pb isotopic analysis of single zircon crystals within a sample may directly image the age composition--but not the chemical composition--of the source region. Rare earth element (REE) abundances have been measured for zircons from a range of common crustal igneous rock types

J. M. Hanchar; R. J. Finch; W. O. Hoskin; E. B. Watson; D. J. Cherniak; A. N. Mariano

2001-01-01

25

[Study on the contents and fractionation of rare earth elements in filtering water and suspensions in Gansu, Ningxia and Inner Mongolia Sections of Yellow River by HR-ICP-MS].  

PubMed

In the present paper, high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) was applied to analyse the contents of rare earth elements (REE) in the filtering water and suspensions from 12 sampling sites in Gansu, Ningxia and Inner Mongolia Sections of Yellow River, and the fractionation of REE in suspensions was also studied. The results demonstrated that the contents of REE in filtering water were very low, and the element with highest content of elements was La(32.0 ng x L(-1)). The average concentration of total REE (sigmaREE) in filtering water was 47.5 ng x L(-1), and the Baotou-Dengkou (S1) and Sanhuhekou (S2) sampling sites had a higher sigmaREE of 130.0 and 100.0 ng x L(-1), which implied that there might be external REE sources in the filtering water. And in suspensions, the average content of sigmaREE was 167.8 mg x kg(-1), which was similar to the Chinese soil background value. While the heavy rare earth elements (HREE) content in Shenchuanqiao (S11) of Gansu province were significantly higher than other stations, which indicated that it might have external HREE sources. The chondrite-normalized patterns of REE in suspensions from the study area were similar to that of Chinese soil, with light rare earth elements enrichment, and moderate Eu depletion and a bit of Ce depletion. It was showed that the contents of REE in suspensions were mainly from soil weathering. PMID:23841440

Liu, Jing-Jun; Han, Dan; Liu, Ying

2013-04-01

26

Rare Earth Elements: End Use and Recycability.  

National Technical Information Service (NTIS)

Rare earth elements are used in mature markets (such as catalysts, glassmaking, lighting, and metallurgy), which account for 59 percent of the total worldwide consumption of rare earth elements, and in newer, high-growth markets (such as battery alloys, c...

T. G. Goonan

2011-01-01

27

Rare Earth Element Mines, Deposits, and Occurrences  

USGS Publications Warehouse

Data on rare earth (including yttrium) mines, deposits, and occurrences were compiled as part of an effort by the USGS and the University of Arizona Center for Mineral Resources to summarize current knowledge on the supply and demand outlook and related topics for this group of elements. Economic competition and environmental concerns are increasingly constraining the mining and processing of rare earths from the Mountain Pass mine in California. For many years, the deposit at Mountain Pass was the world's dominant source of rare earth elements and the United States was essentially self-sufficient. Starting approximately 10 years ago, the U.S. has become increasingly dependent (> 90 percent of separated rare earths) upon imports from China, now the dominant source of rare earths. A knowledge of the known economic and noneconomic sources of rare earths is basic to evaluating the outlook for rare earth supply and associated issues.

Orris, Greta J.; Grauch, Richard I.

2002-01-01

28

Systematic variation of rare-earth elements in cerium-earth minerals  

USGS Publications Warehouse

In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (???), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ??? for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ??? for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ??? is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ??? greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements-efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ??? in one crystal and a slightly smaller value of ??? in the outer part of the other crystal compared to the inner part. The ??? of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ??? of monazites in the intruded host rock. These results indicate that the fractionation of the rare-earth elements is not a simple unidirectional process. When a cerium-earth mineral undergoes replacement, its rare-earth elements may be fractionated into two parts, one forming a new mineral with ??? that is smaller, and the other a second new mineral with ??? that is larger than that of the original mineral. The complete analysis of a cerium-earth mineral to determine its ??? is time consuming. The discovery of a direct relationship between ??? and the Ce/(Nd + Y) atomic ratio in cerium earth minerals allows a rapid determination of ??? from spectrograms obtained in a previously described method for determining thorium in these minerals. ?? 1957.

Murata, K. J.; Rose, Jr. , H. J.; Carron, M. K.; Glass, J. J.

1957-01-01

29

Are highly siderophile elements (PGE, Re and Au) fractionated in the upper mantle of the earth? New results on peridotites from Zabargad  

Microsoft Academic Search

Seven peridotite samples from Zabargad Island (Red Sea) were analyzed for highly siderophile elements (HSE), including five platinum-group elements (PGE: Os, Ir, Ru, Rh, Pd) and Re and Au. Petrography and chemical composition of the samples had been published earlier [Kurat, G., Palme,h., Embey-Isztin, A., Touret, J., Ntaflos, T., Spettel, B., Brandstatter, F., Palme, C., Dreibus, G., Prinz,m., 1993. Petrology

Gerhard Schmidt; Herbert Palme; Karl-Ludwig Kratz; Gero Kurat

2000-01-01

30

TWO EXTRASOLAR ASTEROIDS WITH LOW VOLATILE-ELEMENT MASS FRACTIONS  

SciTech Connect

Using ultraviolet spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, we extend our previous ground-based optical determinations of the composition of the extrasolar asteroids accreted onto two white dwarfs, GD 40 and G241-6. Combining optical and ultraviolet spectra of these stars with He-dominated atmospheres, 13 and 12 polluting elements are confidently detected in GD 40 and G241-6, respectively. For the material accreted onto GD 40, the volatile elements C and S are deficient by more than a factor of 10 and N by at least a factor of 5 compared to their mass fractions in primitive CI chondrites and approach what is inferred for bulk Earth. A similar pattern is found for G241-6 except that S is undepleted. We have also newly detected or placed meaningful upper limits for the amount of Cl, Al, P, Ni, and Cu in the accreted matter. Extending results from optical studies, the mass fractions of refractory elements in the accreted parent bodies are similar to what is measured for bulk Earth and chondrites. Thermal processing, perhaps interior to a snow line, appears to be of central importance in determining the elemental compositions of these particular extrasolar asteroids.

Jura, M.; Xu, S.; Klein, B.; Zuckerman, B. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 (United States); Koester, D., E-mail: jura@astro.ucla.edu, E-mail: sxu@astro.ucla.edu, E-mail: kleinb@astro.ucla.edu, E-mail: ben@astro.ucla.edu, E-mail: koester@astrophysik.uni-kiel.de [Institut fur Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel (Germany)

2012-05-01

31

Ion probe measurement of rare earth elements in biogenic phosphates  

NASA Astrophysics Data System (ADS)

The rare earth element (REE) distributions in individual fish teeth and conodonts have been measured by ion probe. Concentrations and La/Yb ratios show little variations, except in the enamel, which suggests that REE uptake from the sedimented biogenic debris takes place at the water-sediment interface as an essentially quantitative process without fractionation. Late diagenetic disturbances remained of marginal importance. Hence, REE in phosphatic debris might reflect the input from the overlying water column.

Grandjean, Patricia; Albarède, Francis

1989-12-01

32

Light element controlled iron isotope fractionation in planetary cores  

NASA Astrophysics Data System (ADS)

Using iron isotope fractionations measured in planetary and meteorite samples to trace planetary differentiation or formation has yielded contradictory results. Iron from high-Ti lunar basalts is more enriched in 57Fe/54Fe than mantle-derived terrestrial samples, in contrast to the isotopic similarity for almost every other element between the Earth and Moon. SNC (Shergottite, Nakhlite, Chassigny) and HED (Howardite, Eucrite, Diogenite) meteorites, which are thought to be derived from the mantles of Mars and Vesta, respectively, show no isotopic fractionation relative to chondrites. While the Bulk Silicate Earth (BSE) value is debated, recent work has shown effectively that basalts (mid-ocean ridge basalts, terrestrial basalts, and ocean island basalts) are enriched in 57Fe/54Fe relative to chondrites, but the causes of that fractionation are unclear (Craddock et al. 2013). Angrites, basaltic achondrite meteorites, also show enrichment in ?57Fe (Wang et al. 2012). Possible mechanisms include high-pressure core formation, oxidation during perovskite disproportionation, evaporation during the giant impact, and mantle melting. It is important to reconcile why the Earth's basalts are enriched in 57Fe/54Fe but the meteorites from Mars and Vesta are not. One possible explanation is that Mars and Vesta are smaller and the lower pressure attenuated the potential Fe fractionation during core formation. A second possibility is that the intrinsic oxidation states of the planets are causing the differences. However, another option is that the light elements (e.g. S, C, O, H, Si) in the cores of differentiated bodies control the iron isotope fractionation during differentiation. We have conducted experiments at 1 GPa and 1650-1800°C in a piston cylinder apparatus to address how sulfur, carbon and silicon alloyed with iron affect the iron isotopic fractionation between metallic alloy and silicate melt. We find that sulfur has the greatest effect on the iron isotopic fractionation at these conditions.This has wide implications for tracing differentiation processes as the nature of the light element in the core is directly related to the mode of formation and the conditions present. Therefore, by comparing the experimental data with meteoritic data, the composition of planetary cores can be estimated.

Shahar, A.; Hillgren, V. J.; Horan, M. F.; Duke, L.; Mock, T. D.

2013-12-01

33

Rare earth element diffusion in apatite  

Microsoft Academic Search

Diffusion of rare earth elements (REEs) in natural and synthetic fluorapatite has been characterized under anhydrous conditions. Three types of experiments were run. In the first set of experiments, Sm was introduced into the apatite by means of ion implantation, with diffusivities extracted through measurement of the “relaxation” of the implanted profile after diffusion anneals. The second group consisted of

D. J. Cherniak

2000-01-01

34

Isotope fractionation in surface ionization ion source of alkaline-earth iodides  

SciTech Connect

The relationship between the isotope fractionation of alkaline-earth elements in the surface ionization ion source and the evaporation filament current, i.e., filament temperature, was studied. It was confirmed that the isotope fractionation depends on the evaporation filament temperature; the isotope fractionation in the case of higher temperature of filament becomes larger. The ionization and evaporation process in the surface ionization ion source was discussed, and it was concluded that the isotope fractionation is suppressed by setting at the lower temperature of evaporation filament because the dissociations are inhibited on the evaporation filament.

Suzuki, T.; Kanzaki, C.; Nomura, M.; Fujii, Y. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan)

2012-02-15

35

Preparation of microcapsules containing rare-earth metal elements.  

PubMed

Microcapsules for internal radiation therapies containing the rare-earth metal elements Dy, Ho and Cu with a diameter of 5-10 microm were successfully obtained by an interfacial polymerization method and a successive sedimentation technique was employed to fractionate the microcapsules. A triisocyanate monomer and tricresylphosphate were used for a wall forming material and a core solvent for the metals, respectively. The amount of the metal elements loaded was measured using a high frequency plasma photoemission apparatus. The beta-ray radioactivity of 1 mg of microcapsules irradiated with a common neutron source is estimated as 370 microCi, which is satisfactorily strong for usual radiotherapy, when microcapsules containing Dy are used. Differential interference microscopy indicated narrow size distribution of the fractionated microcapulses. PMID:11201336

Shimofure, S; Koizumi, S; Ichikawa, K; Ichikawa, H; Dobashi, T

2001-01-01

36

Study on the absorption of rare earth elements by crops.  

National Technical Information Service (NTIS)

In the rare earth products used in agriculture, there are several main kinds of rare earth elements, such as La, Ce, Pr and Nd. Nearly 99% of rare earth oxides has the composition of La, Ce, Pr and Nd. The process of rare earth elements entering into plan...

Y. Zhu J. Chen

1990-01-01

37

Note: Portable rare-earth element analyzer using pyroelectric crystal  

SciTech Connect

We report a portable rare-earth element analyzer with a palm-top size chamber including the electron source of a pyroelectric crystal and the sample stage utilizing cathodoluminescence (CL) phenomenon. The portable rare-earth element analyzer utilizing CL phenomenon is the smallest reported so far. The portable rare-earth element analyzer detected the rare-earth elements Dy, Tb, Er, and Sm of ppm order in zircon, which were not detected by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. We also performed an elemental mapping of rare-earth elements by capturing a CL image using CCD camera.

Imashuku, Susumu, E-mail: imashuku.susumu.2m@kyoto-u.ac.jp; Fuyuno, Naoto; Hanasaki, Kohei; Kawai, Jun [Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)] [Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)

2013-12-15

38

Anthropogenic Cycles of Rare Earth Elements  

NASA Astrophysics Data System (ADS)

This research will develop quantitatively resolved anthropogenic cycles and in-use stocks for the rare earth metals specifically cerium, lanthanum and dysprosium in Japan, China, and the U.S. for the year of 2007. Rare earth elements (REE) is a group of 17 scare metals widely used in a growing number of emerging technologies and have been in high demand for emerging technologies as raw materials during past the three decades. New market participants from newly industrializing countries, primarily China, have had strong impacts on the demand of share. Consequently, the importance to sustain a reliable, steady, uninterrupted supply on global market triggered comprehensive research to recognize and understand the life cycles of rare earths. Moreover, because China plays a dominant role in mining production since 1990, it requires the assessment for the countries, which are almost completely dependent on imports from China with respect to rare earth resources. The study aims to analyze the flows and stocks of rare earth elements individually as elemental form in spite of their natural geological co-occurrence and mixed composition in applications. By applying the method of Material Flow Analysis (MFA) work has been done on evaluating current and historical flows of specific technologically significant materials, for example, copper, zinc, nickel, etc., determining the stocks available in different types of reservoirs (e.g., lithosphere, in-use) and the flows among the reservoirs, developing scenarios of possible futures of metal use, and assessing the environmental and policy implications of the results. Therefore, REE as a new target deserves inclusion because of its potential demand-supply conflict and importance to secure the competitive advantage of technical innovation in future. This work will generate a quantitatively resolved anthropogenic life cycle and in-use stocks for REE for the main target countries for a chosen year, 2007, providing flows and stocks from mining to use to recycling quantifying the cycles for Japan, China and the U.S. as three representative types of consumers and paying attention to aspects of resource sustainability. Being well aware of the stages in the metal life cycle helps the sustainable development and policy making in long term. The goal is to consider REE resource availability, sustainability, and development strategies in the future that can sustain a reliable, steady, uninterrupted REE supply on the global market.

Du, X.; Graedel, T. E.

2009-12-01

39

Iron isotope fractionation in the Earth's lower mantle  

Microsoft Academic Search

Understanding the distribution of iron isotopes within planetary bodies can help constrain their histories of accretion and differentiation. A large fraction of the iron in the silicate Earth is dissolved in ferropericlase and ferroperovskite-mineral phases that make up the bulk of the lower mantle. These phases have distinct crystallographic structures and iron resides in them in multiple spin states; they

James R. Rustad; Qing-Zhu Yin

2009-01-01

40

Tipping elements in the Earth's climate system  

PubMed Central

The term “tipping point” commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term “tipping element” to describe large-scale components of the Earth system that may pass a tipping point. We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and we assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then we explain how, in principle, early warning systems could be established to detect the proximity of some tipping points.

Lenton, Timothy M.; Held, Hermann; Kriegler, Elmar; Hall, Jim W.; Lucht, Wolfgang; Rahmstorf, Stefan; Schellnhuber, Hans Joachim

2008-01-01

41

Alkaline Element Fractionations in LL-chondritic Breccias  

NASA Astrophysics Data System (ADS)

Introduction: Fractionation of moderately volatile lithophile elements including alkaline elements was an important process in the early solar system. Alkali-rich igneous fragments (K-rich fragments) were found in brecciated LL-chondrites. These fragments in Kraehenberg (LL5), Bhola (LL3-6), and Yamato (Y)-74442 (LL4) show fractionated alkaline element patterns; for example, abundances of alkaline elements in the Kraehenberg fragment are ~0.5 x CI for Na, ~12 x CI for K,~45 x CI for Rb, and ~70 x CI for Cs [1]. In order to understand moderately volatile element fractionations, we have undertaken mineralogical and petrological studies on K-rich fragments in Kraehenberg [1], Bhola [2], and Y-74442 [3, 4]. Results and Discussion: Kraehenberg, Bhola, and Y-74442 consist of mineral fragments, K-rich fragments, impact-melt clasts, chondrules, and matrix. K-rich fragments in these meteorites are composed of 10-100 µm-sized euhedral olivine (~60 vol.%) and groundmass of brown glasses (~40 vol.%, including microcrystalline pyroxene) which are highly enriched in alkaline elements. Dendritic pyroxene and chromite (~1 µm in size) along with troilite (~10 µm in size) are commonly observed in the groundmass. The textures are different from those of impact melt clasts in ordinary chondrites. Chemical compositions of olivine in the K-rich fragments fall within the compositional range of equilibrated LL-chondrites (Fa26-32 [5]). Groundmass glasses in the Kraehenberg, Bhola, and Y-74442 fragments are almost identical in composition when plotted on a Na+K+Al-oxides-Ca+Mg+Fe-oxides-SiO2 ternary diagram [1]. The fractionation trend is also observed in an angular igneous fragment in Siena (LL5) [6]. The lack of K isotopic fractionation effects in the K-rich clast in Kraehenberg [7] implies that the enrichment of (heavier) alkaline elements occurred near-equilibrium conditions. The K-rich fragments in Kraehenberg and Y-74442 could be early solar system materials (~4.56 Ga [8, 9]). Similarities in textures, compositions, and fractionation patterns of the K-rich fragments suggest that they might be formed from related precursor materials with related processes. Complementarity of K-rich fragments and differentiated body alkali abundance patterns suggests that the fractionation could have occurred in the early solar nebula. Refs: [1] Wlotzka F. et al. (1983) Geochim. Cosmochim. Acta 47, 743. [2] Noonan A.F. et al. (1978) Geol. Survey Open File Report 78-701, 311. [3] Yanai K. et al. (1978) Mem. Natl. Inst. Polar Res. Spec. Issue 8, 110. [4] Ikeda Y. and Takeda H. (1979) Mem. Natl. Inst. Polar Res. Spec. Issue 15, 123. [5] Dodd R.T. (1981) Meteorites pp. 368, Cambridge Univ. Press. [6] Fodor R.V. and Keil K. (1978) Catalog of lithic fragments in LL-chondrites, Inst. Meteoritics Spec. Publ. No. 19, pp. 38, Univ. New Mexico, Albuquerque. [7] Humayun M. and Clayton R.N. (1995) Geochim. Cosmochim. Acta 59, 2131. [8] Kempe W. and Mueller O. (1969) Meteorite Res., pp. 418. [9] Nishiya N. et al. (1995) Okayama Univ. Earth Sci. Rep. 2, 91.

Misawa, K.; Yokoyama, T.; Okano, O.

2010-12-01

42

Leapfrog/Finite Element Method for Fractional Diffusion Equation  

PubMed Central

We analyze a fully discrete leapfrog/Galerkin finite element method for the numerical solution of the space fractional order (fractional for simplicity) diffusion equation. The generalized fractional derivative spaces are defined in a bounded interval. And some related properties are further discussed for the following finite element analysis. Then the fractional diffusion equation is discretized in space by the finite element method and in time by the explicit leapfrog scheme. For the resulting fully discrete, conditionally stable scheme, we prove an L 2-error bound of finite element accuracy and of second order in time. Numerical examples are included to confirm our theoretical analysis.

Zhao, Zhengang; Zheng, Yunying

2014-01-01

43

Rare Earth Elements: A Tool for Understanding the Behaviour of Trivalent Actinides in the Geosphere  

SciTech Connect

Rare earth element (REE) concentrations have been determined in groundwaters, granite and fracture fillings in a restored uranium mine. The granitoids normalized REE patterns of groundwaters show heavy rare earth elements (HREE)-enrichment and positive Eu anomalies. This suggests that the REE are fractionated during leaching from the source rocks by groundwaters. Preferential leaching of HREE would be consistent with the greater stability of their aqueous complexes compared to those of the light rare earth elements (LREE), together with the dissolution of certain fracture filling minerals, dissolution/alteration of phyllosilicates and colloidal transport. (authors)

Buil, Belen; Gomez, Paloma; Garralon, Antonio; Turrero, M. Jesus [Medioambiente, CIEMAT, Avda. Complutense 22, Madrid, 28040 (Spain)

2007-07-01

44

Rare earth elements in river waters  

NASA Technical Reports Server (NTRS)

To characterize the input to the oceans of rare earth elements (REE) in the dissolved and the suspended loads of rivers, the REE concentrations were measured in samples of Amazon, Indus, Mississippi, Murray-Darling, and Ohio rivers and in samples of smaller rivers that had more distinct drainage basin lithology and water chemistry. It was found that, in the suspended loads of small rivers, the REE pattern was dependent on drainage basin geology, whereas the suspended loads in major rivers had relatively uniform REE patterns and were heavy-REE depleted relative to the North American Shale composite (NASC). The dissolved loads in the five major rivers had marked relative heavy-REE enrichments, relative to the NASC and the suspended material, with the (La/Yb)N ratio of about 0.4 (as compared with the ratio of about 1.9 in suspended loads).

Goldstein, Steven J.; Jacobsen, Stein B.

1988-01-01

45

Rare Earth Elements in Global Aqueous Media  

NASA Astrophysics Data System (ADS)

We are examining the occurrence and abundance of rare earth elements (REE) associated with produced waters from shale gas development, and factors controlling aqueous REE concentrations in geochemical environments, to provide information for: (1) potential recovery of REE as a valuable byproduct, and (2) utilization of unique REE signatures as a risk assessment tool. REE include the lanthanide series of elements - excluding short-lived, radioactive promethium - and yttrium. These elements are critical to a wide variety of high-tech, energy efficient applications such as phosphors, magnets, and batteries. Escalating costs of REE resulting from divergent supply and demand patterns motivates the first goal. The second goal relates to the search for a reliable, naturally occurring tracer to improve understanding of fluid migration and water-rock interactions during hydraulic fracturing and natural gas recovery. We compiled data from 100 studies of REE occurrence and concentrations in groundwaters, ocean waters, river waters, and lake waters. In the groundwater systems documented, total dissolved REE concentrations ranged over eight orders of magnitude; however the average concentrations across the lanthanides varied by less than two orders of magnitude. This leads to exceptional inter-element correlations, with a median correlation coefficient greater than 0.98, implying potential usefulness of REE ratios for groundwater signatures. Reports describing reactions governing REE solubilization were also investigated. We assembled information about important solution chemistries and performed equilibrium modeling using PHREEQC to examine common hypotheses regarding the factors controlling REE compositions. In particular, effects of pH, Eh, and common complexing ligands were evaluated. Produced and connate waters of the Marcellus shale are well characterized for their major chemical elements. There is a dearth of knowledge, however, regarding the occurrence of REE in Marcellus shale brines and in high TDS brines in general. From synthesis of available brine and geological data, we have developed hypotheses about REE occurrence and content of these hypersaline solutions. It is well documented that the REE concentrations of a solution can serve as a signature of the water and changes in this signature represent interactions with fluids of different compositions or changing mineral strata. We will discuss how the unique signatures and reactivity of REE potentially makes these elements uniquely capable tracers of hydrogeologic activity.

Noack, C.; Karamalidis, A.; Dzombak, D. A.

2012-12-01

46

Geostationary earth observatories - Key elements of NASA's 'Mission to Planet Earth'  

NASA Technical Reports Server (NTRS)

The scientific rationale, required instrumentation, observatory configuration, and data system of the Geostationary Earth Observatory (GEO) element of NASA's Mission to Planet Earth program are discussed. Physical characteristics of GEO candidate instruments are listed.

Snoddy, William C.; Keller, Vernon W.

1991-01-01

47

Chemical fractionations in meteorites--III. Major element fractionations in chondrites  

Microsoft Academic Search

Some 20 elements, including the major constituents of chondritic matter, are fractionated among the several chondrite classes. We have tried to explain these fractionations on the assumption that they occurred in the solar nebula, starting from material of carbonaceous chondrite composition. 1. (1) Lithophile elements (Al, Ca, Cr, Hf, Mg, Sc, Si, Th, Ti, U, Y, Zr, and lanthanides) may

J. W. Larimer; Edward Anders

1970-01-01

48

W/Hf Fractionation in Chondrites and the Earth: Constraints on Timing of Core Formation  

NASA Astrophysics Data System (ADS)

The recent measurements of the Hf and W isotope systematics in terrestrial and meteorite material has led Lee and Halliday to conclude that terrestrial core formation occurred at least 60 Myr after the formation of the iron meteorites. This calculation depends on assumptions regarding the Hf/W ratio for the bulk silicate Earth, and for the ratio in the chondritic material from which the iron meteorites, and the Earth formed. A new study of the abundance and depletion of W in the Earth, relative to refractory lithophile elements, such as Hf, provides constraints on the terrestrial Hf/W ratio. In the chondrites, the ratio of W to refractory lithophile elements is also variable, because W did not fully participate in the metal-silicate fractionation which occurred in the solar nebula. Therefore, the uncertainties in the Hf/W ratios in the chondrites and in the Earth must be considered to determine the constraints on the timing of core formation in the Earth. In the case of the heterogeneous accretion theory, W is accreted to the Earth's primitive mantle in an additive process, which has important implications for the significance of the Hf-W isotope systematics.

Newsom, H. E.

1996-03-01

49

Rare earths and other trace elements in Luna 16 soil.  

NASA Technical Reports Server (NTRS)

An analysis has been made of four small samples of material brought to earth by the Luna 16 mission, with the aim to determine rare earths and other trace elements in these samples. The analytical results are tabulated, and the rare earth abundances are compared with the average for chondrites. A comparison is also made with the results of similar analyses of Apollo samples.

Helmke, P. A.; Haskin, L. A.

1972-01-01

50

Rare earth element partition coefficients in zircon\\/melt systems  

Microsoft Academic Search

In principle, rare earth element (REE) concentrations in magmatic zircon crystals can be used to reconstruct growth conditions, provided accurate information is available about the partitioning of REEs between zircon and magma. Over the past twenty-five years, there have been several studies published that used natural and synthetic samples to determine zircon-melt rare earth element (REE) partition coefficients (D's) in

J. M. Hanchar; W. van Westrenen

2006-01-01

51

Thermochemical Models of Earth's Mantle Convection: New Insight From Fractionation and Outgassing Processes  

NASA Astrophysics Data System (ADS)

As one fundamental part of the global recycling process between the Earth's mantle and lithosphere, sinking slabs in the deep mantle play a crucial role on mantle geochemical evolution. Many previous studies in the mantle dynamics subject area focused on understanding how stirring and mixing acts in the convective mantle, and thus how slab heterogeneities are spread out through the global convective process. However, none of these studies convincingly explained the still unresolved basalt geochemistry paradigm. One must emphasize that this kind of study oversimplified the problem in neglecting the complex petrologic processes at the surface of the Earth that strongly modify the trace element distributions and influence the mixing properties: for example, partial melting at ridges both smooths mantle heterogeneities in efficiently mixing the melt product, but also creates non-homogeneous distributions in fractionating elements. Here, we present the results of numerical models of thermal convection taking into account the effects of partial melting at ridges on trace element distributions (U, Th, He, K, Ar). We use the 2D-cartesian convective code ConMan (King et al 90) to carry out the calculations, and impose plate-like velocities at the surface. Passive tracers with assigned chemical compositions are advected. We input solidus, liquidus and fraction of melt as a function of temperature from petrologic data and compute the resulting fractionation process on the tracers chemical composition. We use several melting laws (fraction of melt, F=f(T), given by a linear function or data-fitted function), we vary the relative fractionation coefficients between the various species, and address their effects on the secular variations of the trace element distributions in the mantle. We are particularily interested in focusing on the resulting deep mantle composition.

Ferrachat, S.; Kellogg, L. H.

2001-12-01

52

Elemental fractionation and stoichiometric sampling in femtosecond laser ablation  

Microsoft Academic Search

Elemental fractionation in femtosecond laser ablation is studied by ICP-MS by applying successive single laser shots to binary metallic and semiconductor samples as well as to multi-component glasses. Fractionation can be observed in the first laser shots in particular if the laser fluence is near the ablation threshold of the sample. However, the element ratio in the laser-sampled masses changes

Carmen C. Garcia; Helmut Lindner; Alex von Bohlen; Cedomil Vadla; Kay Niemax

2008-01-01

53

Cumulative damage fraction design approach for LMFBR metallic fuel elements  

Microsoft Academic Search

The cumulative damage fraction (CDF) analytical technique is currently being used to analyze the performance of metallic fuel elements for proliferation-resistant LMFBRs. In this technique, the fraction of the total time to rupture of the cladding is calculated as a function of the thermal, stress, and neutronic history. Cladding breach or rupture is implied by CDF = 1. Cladding wastage,

D. L. Johnson; R. E. Einziger; G. D. Huchman

1979-01-01

54

Paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite  

Microsoft Academic Search

Rare earth element concentrations in biogenic apatite of conodonts, fish debris and inarticulate brachiopods were determined in over 200 samples from Cambrian to modern sediments. Tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory, interexperiment or interspecies related variations clearly show that no resolvable fractionation of REE occurs. Incorporation of

Judith Wright; Hans Schrader; William T. Holser

1987-01-01

55

Trapping of transuranium elements by the earth's magnetic field  

NASA Technical Reports Server (NTRS)

The search for a transuranium element component of cosmic radiation has been carried out in high altitude balloon experiments. The trapping of high Z elements on orbits in the Earth's magnetic field may lead to a sufficient enhancement of the intensity of particle flux to make it possible to detect these elements by satellite experiments. Calculations are presented that predict the behavior of trapped particles as a function of the predicted flux and energy distribution of high Z elements incident on the Earth's magnetic field. Techniques are suggested for the detection of such particles. In addition, the possibility of production of transuranium elements in the recently discovered pulsars are discussed.

Bloom, J. L.; Eastlund, B. J.

1972-01-01

56

Chemical fractionation of trace elements in coal and coal ash  

Microsoft Academic Search

This article examines the chemical fractionation (leaching) of elements from the Whitewood Mine subbituminous coals and coal ashes at 120 C, 750 C, and 1000 C. The elements Ba, Zn, and Mn are easily leached from coal by water, ammonium acetate, and hydrochloric acid. Potassium is highly extractable by NHâO acetate but very little with HCl. Hydrochloric acid leaches most

T. Gentzis; F. Goodarzi

1999-01-01

57

Earth, Air, Fire and Water in Our Elements  

ERIC Educational Resources Information Center

The idea that everything is made of the four "elements", earth, air, fire and water, goes back to the ancient Greeks. In this article, the author talks about the origins of ideas about the elements. The author provides an account that attempts to summarise thousands of years of theoretical development of the elements in a thousand words or so.

Lievesley, Tara

2007-01-01

58

Volatile element depletion and K-39/K-41 fractionation in lunar soils  

NASA Technical Reports Server (NTRS)

Evidence for selective loss and isotopic fractionation (in the case of K) of volatile elements during formation of agglutinates by micrometeoritic bombardment of lunar soils is presented. Concentrations and isotopic compositions of volatile elements (K, Rb, Pb) and nonvolatile elements (U, Th, Ba, Sr, rare earths) in separates taken from soils 14163, 14259, 15041, 68501, and 71500 are examined. Rayleigh fractionation calculations applied to K-39/K-41 isotopic data indicate ten-fold recycling of bulk soil, to account for observed isotopic anomalies. The lunar soil fines fraction seems to be a site of deposition for volatile or labile Pb produced during agglutination. Local fines (below 75 microns) are viewed as representative of the parent material for agglutinates formed in situ by micrometeoritic impact. Magnetic separation of agglutinates from soil 68501 revealed a bimodal population, with one class comprising welded blocky magnetic glasses.

Church, S. E.; Tilton, G. R.; Wright, J. E.; Lee-Hu, C.-N.

1976-01-01

59

Coupled finite element method for the Earth's orientation parameter problems  

NASA Astrophysics Data System (ADS)

We describe the combined approach to the Earth's orientation parameter problems. The approach allows one to couple the finite element method with the solution of the Laplace equation on the basis of iteration procedure. This makes possible to calculate heterogeneties of both geometrical and rheological characters into the Earth's structure. In the framework of this approach, forced nutation of the simplified dynamical Earth's model is determined and a comparison with the corresponding results of Molodensky and Wahr is carried out.

Lubkov, M. V.

2005-10-01

60

Normalized rare earth elements in water, sediments, and wine: identifying sources and environmental redox conditions  

USGS Publications Warehouse

The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that reveal their partitioning between different sediment fractions and the sources of those fractions, for example, between terrestrial-derived lithogenous debris and seawater-derived biogenous detritus and hydrogenous metal oxides. The REE of ancient sediments support their partitioning into these same fractions and further contribute to the identification of the redox geochemistry of the sea water in which the sediments accumulated. The normalized curves of the REE that have been examined in several South American wine varietals can be interpreted to reflect the lithology of the bedrock on which the vines may have been grown, suggesting limited fractionation during soil development.

Piper, David Z.; Bau, Michael

2013-01-01

61

Rare earth element diffusion in apatite  

NASA Astrophysics Data System (ADS)

Diffusion of rare earth elements (REEs) in natural and synthetic fluorapatite has been characterized under anhydrous conditions. Three types of experiments were run. In the first set of experiments, Sm was introduced into the apatite by means of ion implantation, with diffusivities extracted through measurement of the "relaxation" of the implanted profile after diffusion anneals. The second group consisted of "in diffusion" experiments, in which apatite was immersed in reservoirs of synthetic REE apatite analogs of various compositions. The final set of experiments was "out-diffusion" experiments run on synthetic Nd-doped apatite immersed in a reservoir of synthetic (undoped) fluorapatite. REE depth profiles in all cases were measured with Rutherford Backscattering Spectrometry. Diffusion rates for the REE vary significantly among these sets of experiments. For the ion-implantation experiments, the following Arrhenius relation was obtained for Sm, over the temperature range 750°C to 1100°C: D imp=6.3×10-7exp(-298±17 kJ/mol/RT) m2/s Diffusion of a series of REE, from light to heavy, was investigated in the "in-diffusion" experiments. Over the temperature range 800°C to 1250°C, the following Arrhenius relations are obtained for La, Nd, Dy, and Yb, for in-diffusion experiments using REE silicate oxyapatite sources: D La=2.6×10-7exp(-324±9 kJ/mol/RT) m2/sD Nd=2.4×10-6exp(-348±13 kJ/mol/RT) m2/sD Dy=9.7×10-7exp(-340±11 kJ/mol/RT) m2/sD Yb=1.3×10-8exp(-292±23 kJ/mol/RT) m2/s Diffusivities of the REE in these "in-diffusion" experiments are all quite similar, suggesting little difference in diffusion rates in apatite with increasing ionic radii of the REEs. The "out-diffusion" experiments on the Nd-doped synthetic apatite, over the temperature range 950°C to 1400°C, yield the Arrhenius law: D out=9.3×10-6exp(-392±31 kJ/mol/RT) m2/s The differences in REE diffusion among these three sets of experiments (i.e., ion implantation, in-diffusion, and out-diffusion) may be attributable to the differences in substitutional processes facilitating REE exchange. The fastest diffusion, found in the ion-implantation experiments, is likely largely governed by simple light REE +3 ? REE +3 exchange, with no charge compensating species necessary. REE transport in the in-diffusion experiments requires movement of an additional charge-compensating species, either through the substitutions REE +3 + Si +4 ? Ca +2 + P +5 or REE +3 + Na +1 ? 2 Ca +2, and thus proceeds more slowly than simple REE exchange. Slowest of all is Nd out-diffusion from the synthetic Nd-doped apatite, for which neither charge compensating species are present nor REEs available in the surrounding reservoir to facilitate Nd exchange. This observed dependence of REE diffusion rates on the exchange process involved has important geochemical implications. These findings indicate that REE isotope and chemical signatures can become decoupled in apatite, with light REE isotope exchange proceeding much more rapidly than REE chemical diffusion altering total REE concentrations. Under temperatures typical of thermal events, REE zoning (involving differences in REE concentration across zones) of a given dimension might persist over time periods two orders of magnitude greater than those under which zoning of REE isotopes (without significant changes in total REE) on similar scale is preserved.

Cherniak, D. J.

2000-11-01

62

Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon  

NASA Technical Reports Server (NTRS)

Depletions of volatile siderophile elements (VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd) in mantles of Earth and Moon, constrain the origin of volatile elements in these bodies, and the overall depletion of volatile elements in Moon relative to Earth. A satisfactory explanation has remained elusive [1,2]. We examine the depletions of VSE in Earth and Moon and quantify the amount of depletion due to core formation and volatility of potential building blocks. We calculate the composition of the Earth's PUM during continuous accretion scenarios with constant and variable fO2. Results suggest that the VSE can be explained by a rather simple scenario of continuous accretion leading to a high PT metal-silicate equilibrium scenario that establishes the siderophile element content of Earth's PUM near the end of accretion [3]. Core formation models for the Moon explain most VSE, but calculated contents of In, Sn, and Zn (all with Tc < 750 K) are all still too high after core formation, and must therefore require an additional process to explain the depletions in the lunar mantle. We discuss possible processes including magmatic degassing, evaporation, condensation, and vapor-liquid fractionation in the lunar disk.

Righter, Kevin; Pando, K.; Danielson, L.; Nickodem, K.

2014-01-01

63

Fractional generalization of memristor and higher order elements  

NASA Astrophysics Data System (ADS)

Fractional calculus generalizes integer order derivatives and integrals. Memristor systems generalize the notion of electrical elements. Both concepts were shown to model important classes of phenomena. This paper goes a step further by embedding both tools in a generalization considering complex-order objects. Two complex operators leading to real-valued results are proposed. The proposed class of models generate a broad universe of elements. Several combinations of values are tested and the corresponding dynamical behavior is analyzed.

Tenreiro Machado, J.

2013-02-01

64

China's Rare Earth Elements Industry: What Can the West Learn.  

National Technical Information Service (NTIS)

China controls approximately 97 percent of the world's rare earth element market. These elements, which are not widely known because they are so low on the production chain, are critical to hundreds of high tech applications, many of which define our mode...

C. Hurst

2010-01-01

65

Inaugural Article: Tipping elements in the Earth's climate system  

Microsoft Academic Search

The term ``tipping point'' commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term ``tipping element'' to describe large-scale components of the Earth system that may pass a tipping point. We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing,

Timothy M. Lenton; Hermann Held; Elmar Kriegler; Jim W. Hall; Wolfgang Lucht; Stefan Rahmstorf; Hans Joachim Schellnhuber

2008-01-01

66

Perturbations in orbital elements of a low earth orbiting satellite  

Microsoft Academic Search

The main point of this paper is to evaluate the perturbations in orbital elements of a low Earth orbiting satellite. The outcome of a numerical orbit integration process is the position and velocity vectors of satellite in an inertial coordinate system. The velocity and position vectors are converted into the corresponding orbital elements. Perturbations in a satellite motion affect the

Najafi Alamdari; Nasir Toosi

67

Countering China's Dominance in the Rare Earth Element Market System.  

National Technical Information Service (NTIS)

This paper will discuss how the United States can exercise the economic element of national power to ensure access to rare earth elements (REE) in a China-dominated market system. Since the 1980 s, China has gained a virtual monopoly in the mining and pro...

E. O. Estep

2012-01-01

68

Early Earth`s climate: Cloud feedback from reduced land fraction and ozone concentrations  

SciTech Connect

Two features of early Earth - reduced ozone (O{sub 3}) concentration and land fraction are investigated with a general circulation model (GCM). These features are components of a paradox (Faint-Young Sun paradox) which has intrigued researchers for more than two decades. In this study, land fraction and O{sub 3} concentrations are uniformly reduced by 100 percent. The reduction of O{sub 3} takes place in the troposphere and stratosphere with all other variables held constant including present-day land fraction. Two sensitivity tests under global ocean conditions are reported: one case with implied oceanic poleward transports of heat, the other case with no implied oceanic poleward transports of heat. The results show that the removal of land under present-day conditions increases cloud fractions and cool surface temperatures, unless heat is transported poleward by oceans. In a third sensitivity test with zero O{sub 3} concentrations, global mean air temperatures are increased by 2 K because of an increase in upper tropospheric and lower stratospheric clouds. The clouds enhance the greenhouse effect within the troposphere, increasing downward longwave radiation to the surface, melting sea ice and snow. Similar studies using radiative-convective models which do not include interactive clouds do not show such surface warming. 24 refs., 3 figs., 1 tab.

Jenkins, G.S.

1995-06-15

69

Carbon and nitrogen isotope fractionation during possible organic aerosol formation in Titan and the early Earth  

NASA Astrophysics Data System (ADS)

Abiotic formation of complex organic macromolecule aerosols is important not only for the potential for prebiotic chemical evolution, but also in the global elemental cycle. The direct clues of the habitable environment and biosphere on the early Earth are mostly obtained from geological records, such as isotope signatures and biomarkers in the ancient organic sediments. The recent Cassini-Huygens mission revealed the generation of complex organic aerosols in Titan's upper atmosphere, and similar processes could have lead to the formation of organic aerosols in the early Earth atmosphere. Understanding the formation reaction network and accompanying isotope fractionation processes of the organic aerosols is necessary to constrain the active organic environment on the early Earth from the available geological evidence. We have investigated the abiotic formation of organic aerosols in simulated atmospheres of Titan and the early, with particular focus on carbon and nitrogen isotope fractionation. Laboratory aerosol analogues, termed tholins, are generated with cold plasma irradiation of reduced gas mixtures, such as N2/CH4 and N2/H2/CO. Stable isotopic ratios of 15N/14N and 13C/12C for the generated tholins are measured with an elemental analysis-isotope ratio mass spectrometer (EA-IR-MS). Our preliminary data for tholins generated from an equivalent N2/CH4 (=90/10) gas mixture at various pressures suggests the 15N isotopic fractionation up to ?15N = -20~25 permil during tholin formation, while 13C isotopic fractionation seems almost negligible. This negative ?15N is even lighter than those observed in kerogens in the Archean sediments (Beaumont and Robert, 1999; Pinti et al., 2001), and the organic haze could have contributed to the source of 15N-depleted kerogens. Furthermore, the ?15N vary with deposition pressure. Previous works demonstrated that the resulted two types of tholin are very different in chemical structure and optical properties (Imanaka et al., 2004, 2012). Although the correlation of pressure might be just an apparent one, distinct type of chemistry could be the reason of such isotopic fractionation. The two distinct ?15N could be related to the difference of dominant functional groups, such as -NH2 and -CN. Since N-H functionality is more abundant in the tholins with depleted 15N, the observed isotopic fractionation could be related to the chemical bond change from N2 to -N-H functionality.

Imanaka, H.

2012-12-01

70

Attenuation of rare earth elements in a boreal estuary  

NASA Astrophysics Data System (ADS)

This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6‰). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the <1 kDa pool became depleted in the middle REE and the colloidal (0.45 ?m-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (<0.45 ?m) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

Åström, Mats E.; Österholm, Peter; Gustafsson, Jon Petter; Nystrand, Miriam; Peltola, Pasi; Nordmyr, Linda; Boman, Anton

2012-11-01

71

Rare earth elements in scleractinian cold-water corals  

NASA Astrophysics Data System (ADS)

The Rare Earth Elements (REE) have a great potential to trace continental input, particle scavenging and the oxidation state of seawater. These REE are recorded in the skeleton of the cosmopolitan cold-water corals Lophelia pertusa. Here we use an online preconcentration ICP-MS method (Hathorne et al. 2012) to measure REE concentrations in seawater and associated cold-water coral carbonates in order to investigate their seawater origin. Scleractinian cold-water corals were collected in-situ and alive and with corresponding seawater samples covering from the European Continental Margin. The seawater REE patterns are characterized by the typical negative cerium anomaly of seawater, but are distinct for the northern Norwegian Margin and the Oslo Fjord, probably related to continental input. Initial results for the corresponding coral samples suggest that these distinct REE patterns of ambient seawater are recorded by the coral skeletons although some fractionation during incorporation into the aragonite occurs. This indicates that scleractinian cold-water corals can serve as a valuable archive for seawater derived REE signatures, as well radiogenic Nd isotope compositions. In a second step we analysed fossil coral samples from various locations, which were oxidatively and reductively cleaned prior to analysis. Initial results reveal that sediment-buried fossil (early Pleistocene to Holocene) coral samples from the Norwegian Margin and the Porcupine Seabight (Challenger Mound, IODP Site 1317) do not show the expected seawater REE patterns. In particular, the fossil coral-derived REE patterns lack a negative cerium anomaly suggesting that fossil coral-REE patterns do not represent ambient seawater. Thus, we suggest that the oxidative-reductive cleaning method widely used for cleaning of marine carbonates such as foraminifera prior to measurements of seawater-derived trace metal and isotope compositions are not sufficient for REE and Nd isotopes in sediment-buried coral-water corals and require alternative or additional approaches. Hathorne, E.C., B. Haley, T. Stichel, P. Grasse, M. Zieringer, and M. Frank (2012). Online preconcentration ICP-MS analysis of rare earth elements in seawater, Geochem. Geophys. Geosyst.,13, Q01020, doi:10.1029/2011GC003907. .

Raddatz, J.; Liebetrau, V.; Hathorne, E. C.; Rüggeberg, A.; Dullo, W.; Frank, M.

2012-12-01

72

Concentration levels of rare-earth elements and thorium in plants from the Morro do Ferro environment as an indicator for the biological availability of transuranium elements  

Microsoft Academic Search

Plants and soils from a natural thorium and rare-earth element occurrence (Morro do Ferro, Brazil) were analyzed by alpha spectrometry (Th) and ICP-AES (REE), after pre-concentration of the elements by solvent extraction, co-precipitation and ion exchange procedures. Leaching experiments with humic acid solutions and different soils were performed to estimate the fraction of elements biologically available. High concentrations of the

N. Miekeley; E. A. Casartelli; R. M. Dotto

1994-01-01

73

Anthropogenic disturbance of element cycles at the Earth's surface.  

PubMed

The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts (Klee and Graedel, 2004). We quantify anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compare it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions, and for helium, hydrodynamic escape from the Earth's atmosphere. We introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporate uncertainties of element mass fluxes through Monte Carlo simulations. We find that at the Earth's surface anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium currently exceed natural fluxes. For these elements mining is the major factor of anthropogenic influence, whereas petroleum burning strongly influences the surficial cycle of rhenium. Our assessment indicates that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements surpass their corresponding natural fluxes. PMID:22803636

Sen, Indra S; Peucker-Ehrenbrink, Bernhard

2012-08-21

74

Rare Earth Element Patterns in Biotite, Muscovite and Tourmaline Minerals.  

National Technical Information Service (NTIS)

Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10 sup -4 ...

J. C. Laul E. A. Lepel

1986-01-01

75

?-decay of neutron-rich Zâ¼60 nuclei and the origin of rare earth elements  

NASA Astrophysics Data System (ADS)

A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a ?-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z˜60 that are progenitors of the rare-earth elements with mass number A˜460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

Wu, J.; Nishimura, S.; Lorusso, G.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Ideguchi, E.; Isobe, T.; Li, Z.; Patel, Z.; Rice, S.; Simpson, G.; Sinclair, L.; Söderström, P. A.; Sumikama, T.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Aoi, N.; Garrote, F. L. Bello; Benzoni, G.; Gey, G.; Gottardo, A.; Nishibata, H.; Odahara, A.; Sakurai, H.; Tanaka, M.; Taprogge, J.; Yamamoto, T.; Eurica Collaboration

2014-05-01

76

Highly Siderophile Element Fractionation During Magma Transport in the Mantle  

NASA Astrophysics Data System (ADS)

Compared to mantle rocks, MORBs and many OIBs show very low, but fractionated PGE abundances (e. g., Hertogen et al., 1980; Rehkämper et al., 1999; Bezos et al. 2005). The basalt data have been explained by fractional crystallization of sulfides, olivine, and possibly alloy phases or chromite (e. g., Rehkämper et al., 1999; Mallmann and O’Neill, 2007). Where these fractionations occur, and what the actual HSE compositions of near-primary mantle melts are, remain open questions. Here we examine evidence for HSE fractionation during magma transport in the mantle. Strongly fractionated highly siderophile element patterns (HSE, the PGE, Re and Au) and relatively high Re abundances of mantle pyroxenites indicate close affinities of these rocks with basalts. This may come hardly as a surprise if pyroxenites represent high-pressure cumulates or melting residues of basic rocks. Sulphide compositions and subparallel HSE patterns of pyroxenite whole rocks suggest that their HSE abundances reflect variable precipitation of sulphides from silicate melt, and thus should be controlled by sulphide-silicate partitioning. Detailed work shows that absolute and relative HSE abundances in some pyroxenites vary with proximity of the peridotite wall rock. Major element, HSE and Os isotopic compositions of Cr diopside websterite and orthopyroxenite rocks suggest that these rocks crystallized from hybrid melts. Such melts likely were modified during reactive infiltration of peridotite, causing dissolution of olivine, Cr spinel and HSE bearing sulphides. Sulfides with melt like and peridotite like compositions in websterites may indicate that some peridotite derived sulphides may have never completely dissolved in these hybrid melts (van Acken et al., in press). Contamination with unradiogenic Os from peridotite results in dramatic shifts of the Os isotopic composition from highly radiogenic in unmodified melts to moderately suprachondritic in hybrid melts and their precipitates. Most HSE have very high sulphide-silicate partitioning coefficients (e. g., Bezmen et al. 1994; Sattari et al., 2002, Mallmann and O’Neill, 2007). Thus, basaltic magmas that precipitated sulphides in the mantle must have lost a substantial fraction of their HSE inventory. Parent melts of Mg rich pyroxenites, i. e. hybrid melts produced during reactive infiltration of peridotite, may be a logical source of the chondritic to moderately suprachondritic Os isotopic composition of basalts and their fractionated HSE pattern. Little reacted Ca-Al rich clinopyroxenites may more closely mirror the HSE pattern and Os isotopic composition of “pristine” mantle melts. If such reaction and infiltration processes are common in the upper mantle, it is difficult to imagine how true pristine source signatures of HSE and Os isotopic compositions can be preserved in basalts.

Becker, H.; van Acken, D.; Fischer-Goedde, M.

2009-12-01

77

Uncovering the end uses of the rare earth elements.  

PubMed

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging and conventional established technologies. However, quantitative knowledge of REE remains sparse, despite the current heightened interest in future availability of the resources. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supply vulnerable to short term disruption. We have drawn upon the published literature and unpublished materials in different languages to derive the first quantitative annual domestic production by end use of individual rare earth elements from 1995 to 2007. The information is illustrated in Sankey diagrams for the years 1995 and 2007. Other years are available in the supporting information. Comparing 1995 and 2007, the production of the rare earth elements in China, Japan, and the US changed dramatically in quantities and structure. The information can provide a solid foundation for industries, academic institutions and governments to make decisions and develop strategies. PMID:23602698

Du, Xiaoyue; Graedel, T E

2013-09-01

78

Logarithmic Distribution Coefficients of Rare Earth Compounds Fractionally Precipitated from Homogeneous Solution.  

National Technical Information Service (NTIS)

A study of the fractional precipitation of the rare earth iodates from homogeneous solution using double complexation and replacement was made. The Doerner-Hoskins logarithmic distribution coefficient (lambda) has been found for a variety of combinations ...

F. H. Firsching G. W. Atom H. N. Meggos R. S. Bakowski M. R. Klotz

1968-01-01

79

Rare earth element partition coefficients in zircon/melt systems  

NASA Astrophysics Data System (ADS)

In principle, rare earth element (REE) concentrations in magmatic zircon crystals can be used to reconstruct growth conditions, provided accurate information is available about the partitioning of REEs between zircon and magma. Over the past twenty-five years, there have been several studies published that used natural and synthetic samples to determine zircon-melt rare earth element (REE) partition coefficients (D's) in geological systems. These data show a remarkable range in values covering several orders of magnitude for some REEs, pointing to as yet unquantified effects of pressure, temperature and/or composition on zircon-melt D's. This calls into question the validity of using these data to calculate the REE composition of co-existing melts. To be able to quantify the effects of P, T and X on zircon-melt partitioning, a theoretical framework to interpret zircon-melt D's is required. As a first step towards this framework, we assessed literature zircon-melt REE D's using the lattice strain model proposed by Blundy and Wood (1994). This model assumes that the primary factor influencing elemental partitioning into a mineral is the strain caused by substituting a trace element into a crystal lattice site. Unconstrained fits to available data give physically unrealistic values for Ro [optimum radius of the zircon Zr site]; Do [(theoretical) strain-free partition coefficient]; and E [apparent Young's Modulus]. Using the well- constrained partitioning data from Hanchar et al. (2001), we derive improved constraints on the relation between E and r0, allowing far more realistic fits to literature data. From the resulting fits it is clear that many LREE D's show significant positive deviations from trends predicted by the lattice strain model. This may reflect analytical problems or mineral inclusions (e.g., monazite), and makes them unsuitable for use in geochemical modelling. The data reported by Sano et al. (2001) for an ion-probe study of REE partitioning between silicate glass, zircon and apatite appear most consistent with lattice-strain based expectations. References Blundy, J., and Wood, B. (1994) Prediction of crystal-melt partition coefficients from elastic moduli. Nature, 372, 452-454. Hanchar, J.M., Finch, R.J., Hoskin, P.W.O., Watson, E.B., Cherniak, D.J., and Mariano, A.N. (2001) Rare earth elements in synthetic zircon. 1. Synthesis and rare earth element and phosphorus doping. American Mineralogist 86: 667-680. Sano, Y., Terada, K., Fukuoka, T. (2001) Ion microprobe analysis of rare earth elements in silicate glass, apatite, and zircon. Eleventh Annual V.M. Goldschmidt Conference, Abstract # 3310, LPI Contribution No. 1088, Lunar and Planetary Institute, Houston (CD-ROM).

Hanchar, J. M.; van Westrenen, W.

2006-12-01

80

Rare earth element budgets in subduction-zone fluids  

NASA Astrophysics Data System (ADS)

Subduction zone fluids play a fundamental role in the geochemical cycle of the Earth. The nature and composition of these fluids are determined by complex processes and still poorly understood. As a result of a variety of metasomatic and partial melting events, arc-related magmas display a typical trace element abundance spectrum, in which the rare earth elements' (REE) signature is an important record of petrogenetic processes. Therefore, investigating the behavior of REE in fluids at high pressure (P) and temperature (T) conditions is crucial for constraining fluid composition, as well as understanding subduction-zone processes in general. However, up to date, the experimental studies on REE solubility and speciation are limited to quite low P-T conditions (300 °C, saturated water vapor pressure) [1]. The theoretical predictions of the stability of REE complexes have been performed up to 350 °C [2] and 1000 °C, 0.5 GPa [3] by the extrapolation of thermodynamic data obtained at ambient conditions. In this study we present new experimental data on REE silicate (REE2Si2O7) solubility in aqueous quartz saturated fluids, containing various ligands, at conditions relevant for subducting slabs (600, 700, 800 °C, 2.6 GPa). The aim of the experiments was to investigate the relative effect of temperature and ligands on the solubility of REE. The experiments were conducted in an end-loaded piston-cylinder apparatus and the fluids were in situ sampled at P-T in the form of primary fluid inclusions in quartz [4]. The gold capsule was typically loaded with a chip of synthetic REE silicate (La,Nd,Gd,Dy,Er,Yb)2Si2O7, an aqueous fluid (~20 wt.%) and a piece of natural quartz. During the experiment (24-48 h) a thermal gradient along the capsule promoted intensive dissolution of quartz at the hottest part and precipitation of new quartz at the cooler part of the capsule, allowing the primary fluid inclusions to be trapped (~30-50 ?m). Rubidium and cesium were added to the fluid as the internal standards for LA-ICPMS analyses. The solubility of REE in quartz saturated water, free of additional ligands, increases more than an order of magnitude as temperature is increased from 600 °C to 800 °C. The effect of halogen ligands (Cl-, F-) on the solubility of REE was tested on experiments conducted at 800 °C. Addition of 1.5 m NaCl enhances the solubilities of all REE by a factor of 2 to 4 and induces moderate LREE/HREE fractionation; the La/Yb ratio increases by factor of 2. Unlike chlorine, the presence of fluorine ligands in the fluid (0.3 m NaF) promotes increase in HREE solubilities with almost no change in LREE solubilities compared to water, hence decreasing the La/Yb ratio by a factor of 2. The results of our experiments suggest that temperature plays an important role in mobilization of all REE by fluids. The presence of Cl- and F- ligands in the fluid shows opposing effects on the REE pattern: Cl- seems to be a more efficient ligand for LREE, while F- tends to form more stable complexes with HREE. [1] Migdisov A. A. et al., 2009, Geochim Cosmochim Acta, 73, 7087-7109 [2] Wood S. A. 1990b, Chem Geo., 82, 159-186 [3] Haas J. R. 1995, Geochim Cosmochim Acta, 59, 4329-4350 [4] Bali E. et al., 2011, Contrib Mineral Petrol, 161, 597-613

Tsay, A.; Zajacz, Z.; Sanchez-Valle, C.

2012-12-01

81

Deep water rare earth element composition in the Cenozoic  

Microsoft Academic Search

The utility of hydrothermal metalliferous sediments in examining past deep water composition has recently been explored through the generation of high-resolution records for both Nd isotopes and rare earth elements (RRE) from the East Pacific Rise (SEPR, 11oS, 3100m). REEs are dominated (96%) by seawater REEs adsorbed to Fe particles in these metalliferous carbonates; the hydrothermal source itself is negligible.

D. Delanghe-Sabatier; R. Sherrell; J. Wright; B. Hamelin

2003-01-01

82

Rare earth elements as geochemical tracers of regional groundwater mixing  

Microsoft Academic Search

The rare earth elements (REE) were analyzed in a groundwater system from south-central Nevada (i.e., Ash Meadows National Wildlife Refuge, the Spring Mountains, Pahranagat National Wildlife Refuge, and the Nevada Test Site) in order to investigate their potential use as tracers of regional groundwater flow. Previous investigations using conservative tracers (e.g., deuterium and uranium isotopes) identified recharge in local mountains

Kevin H. Johannesson; Klaus J. Stetzenbach; Vernon F. Hodge

1997-01-01

83

Condensation and fractionation of rare earths in the solar nebula  

Microsoft Academic Search

Using the most recent thermodynamic data, we calculated the condensation behavior of REE and investigated several models to explain 'group II' REE patterns in Allende inclusions. All models involve removal of large fractions of the more refractory heavy REE in an early condensate, probably perovskite, followed by condensation of the remainder at lower temperature. BOYNTON (1975 Geochim. Cosmochim Acta 39,

ANDREW M. DAMS

84

Uncovering the Global Life Cycles of the Rare Earth Elements  

PubMed Central

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, critical technologies. Knowledge of the life cycles of REE remains sparse, despite the current heightened interest in their future availability. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supplies vulnerable to short and long-term disruption. To provide an improved perspective we derived the first quantitative life cycles (for the year 2007) for ten REE: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and yttrium (Y). Of these REE, Ce and Nd in-use stocks are highest; the in-use stocks of most REE show significant accumulation in modern society. Industrial scrap recycling occurs only from magnet manufacture. We believe there is no post-customer recycling of any of these elements.

Du, Xiaoyue; Graedel, T. E.

2011-01-01

85

Aquatic geochemistry of the rare earth elements and yttrium in the Pioneer River catchment, Australia  

Microsoft Academic Search

The rare earth elements are strong provenance indicators in geological materials, yet the potential for tracing provinciality in surface freshwater samples has not been adequately tested. Rare earth element and yttrium concentrations were measured at 33 locations in the Pioneer River catchment, Mackay, central Queensland,Australia. The rare earth element patterns were compared on the basis of geological, topographical and land-use

Michael G. LawrenceA; Stacy D. JupiterB; Balz S. KamberC

2006-01-01

86

Anthropogenic Disturbance of Element Cycles at the Earth's Surface  

NASA Astrophysics Data System (ADS)

The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts [1]. We determine anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compared it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions and - for helium - hydrodynamic escape from the Earth's atmosphere. In addition, we introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporated uncertainties of element mass fluxes through Monte Carlo simulations [2]. Our assessment indicates that anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium are greater than the respective natural fluxes. For these elements mining is the major factor of human dominance, whereas petroleum burning strongly influence the surficial cycle of rhenium. Apart from these 11 elements there are 15 additional elements whose anthropogenic fluxes may surpass their corresponding natural fluxes. Anthropogenic fluxes of the remaining elements are smaller than their corresponding natural fluxes although a significant human influence is observed for all of them. For example, ~20% of the annual fluxes of C, N, and P can be attributed to human activities. Such disturbances, though small compared with natural fluxes, can significantly alter concentrations in near-surface reservoirs and affect ecosystems if they are sustained over time scales similar to or longer than the residence time of elements in the respective reservoir. Examples are the continuing input of CO2 to the atmosphere that has led to a 40% increase in atmospheric CO2 concentrations, and the atmospheric redistribution of reactive nitrogen and accumulation in remote ecosystems. We note that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements may surpass their corresponding natural fluxes. [1] Klee and Graedel (2004), Annu. Rev. Environ. Resour., 29, p. 69-107 [2] Sen and Peucker-Ehrenbrink (2012), Environ. Sci. Technol., dx.doi.org/10.1021/es301261x

Sen, I. S.; Peucker-Ehrenbrink, B.

2012-12-01

87

Low Earth orbit satellite attitude control by fractional control laws  

NASA Astrophysics Data System (ADS)

Dans cet article, le controle d'attitude trois-axes d'un satellite par roues de reaction est etabli par les methodes fractionnaires. Dans le but d'expliquer les avantages de ces methodes, une etude comparative a etablie entre la methode lineaire quadratique (LQR) et la methode fractionnaire (FOC). Le but de cette etude est de realiser une loi de controle efficace satisfaisant des specifications donnees, et maintenant la stabilite et les performances requises meme en presence des incertitudes sur les parametres intrinsiques du systeme et sous l'effet des perturbations externes. Mots-cles : controle fractionnaire ; controle d'attitude trois-axes ; roues de reaction ; systeme quasi-bilineaire ; controle optimal. Abstract Fractional order control (FOC) methods are applied to the three-axis reaction wheels satellite attitude control. In order to show the advantages of this method, a comparative study between a Linear Quadratic Regulator (LQR) and a FOC is established through two principal fractional control laws. The aim of this paper is to establish an efficient control law which satisfies a given specifications, and maintains sufficient stability and accuracy even under the strong effects of intrinsic parameters uncertainties, and also external perturbations. Keywords: fractional control; 3-axis attitude control; reaction wheels; quasi-bilinear system; optimal control

Kailil, A.; Mrani, N.; Abid, M.; Touati, M. Mliha; Choukri, S.; Elalami, N.

2004-11-01

88

Fractionation and reactivity of platinum group elements during estuarine mixing.  

PubMed

The fractionation of platinum group elements (PGE) rhodium(III), palladium(II), and platinum(IV), has been studied after their addition in aqueous form to unfiltered river water samples (Tugela river, South Africa) and to mixtures of river water and seawater. The particulate fraction of PGE averaged about 70 (Rh), 50 (Pd), and 25% (Pt) of total metal and was dependent on both particle concentration and salinity. The aqueous (<0.45 microm) pool of PGE was dominated by entities of less than 0.1 microm in diameter, and for Pd and Rh hydrophobic complexes of metal, operationally defined by their retention on a C-18 column, were significant. Distribution coefficients, based on the w/w concentration of metal on particles relative to the corresponding concentration in the aqueous pool, either increased (Rh and Pd) or declined (Pt) with increasing salinity. These observations are interpreted in terms of a number of general and metal-specific mechanisms. Thus, the behavior of Pd appears to be controlled by its association with relatively small (<0.1 microm) dissolved organic ligands, a significant fraction of which is hydrophobic and is subject to salting out upon estuarine mixing. Rhodium may also be partly subject to this mechanism of removal, but kinetic considerations and results of X-ray analysis of filter-retentates suggest that adsorption of cationic hydroxychlorides and the destabilization and precipitation of hydroxy-complexes induced by the rise in pH across the estuarine gradient are more important. Unlike Pd, the binding of Pt by organic ligands is kinetically hindered. Thus, in contrast to Pd, particle-water reactivity of Pt is controlled by electrostatic interactions between the particle surface and inorganic aqueous species. The results of this study improve our understanding of and ability to predict the transport and fate of PGE in estuaries where these metals are mobilized or discharged. PMID:18351078

Cobelo-Garcia, Antonio; Turner, Andrew; Millward, Geoff E

2008-02-15

89

Trace element fractionation during fluid-induced eclogitization in a subducting slab: trace element and Lu Hf Sm Nd isotope systematics  

NASA Astrophysics Data System (ADS)

Spatially closely associated gabbros and eclogites of central Zambia represent relics of subducted oceanic crust in a suture zone. The eclogites, which formed at 630-690 °C and 2.6-2.8 GPa, yield Lu-Hf ages between 607±14 and 659±14 Ma, suggesting that subduction was active for at least 24 Myr. The trace element- and isotope compositions of the gabbros and eclogites range from those of incompatible-element depleted gabbros from the lower oceanic crust to those of enriched ocean-island basalts. Several eclogites display a large fractionation of the light rare earth elements from heavy rare earth- and high field strength elements, an effect that cannot be of magmatic origin but must have resulted from the passage of fluids through the rocks during metamorphism. In some samples, fluid pathways are marked by veins of eclogite facies minerals. Garnet-whole rock ages based on the Sm-Nd (relatively mobile) and Lu-Hf (relatively immobile) systems are identical, consistent with light rare earth elements being fractionated during eclogitization. Modeling using fluid-mineral partition coefficients suggests that the fractionated rocks have reacted with an amount of fluid equal up to 80% of their mass. The most likely source for such a large volume of fluid is the serpentinized lithospheric mantle of the subducting slab. The Zambian eclogites and their veins represent relict fluid pathways through subducted oceanic crust and provide direct evidence for channelized fluid flow and element transport within a slab. The transformation of dry, metastable slab gabbros to eclogites upon fluid-infiltration, accompanied by the transport of fluid-mobile elements, could be responsible for generating the slab component in arc magmas.

John, Timm; Scherer, Erik E.; Haase, Karsten; Schenk, Volker

2004-11-01

90

Determination of the Light Element Fraction in MSL APXS Spectra  

NASA Astrophysics Data System (ADS)

Additional light invisible components (ALICs), measured using the alpha particle X-ray spectrometer (APXS), represent all light elements (e.g. CO3, OH, H2O) present in a sample below Na, excluding bound oxygen. The method for quantifying ALICs was originally developed for the Mars Exploration Rover (MER) APXS (Mallet et al, 2006; Campbell et al, 2008). This method has been applied to data collected by the Mars Science Laboratory (MSL) APXS up to sol 269 using a new terrestrial calibration. ALICs are investigated using the intensity ratio of Pu L-alpha Compton and Rayleigh scatter peaks (C/R). Peak areas of the scattered X-rays are determined by the GUAPX fitting program. This experimental C/R is compared to a Monte Carlo simulated C/R. The ratio of simulated and experimental C/R values is called the K-value. ALIC concentrations are calculated by comparing the K-value to the fraction of all invisibles present; the invisible fraction is produced from the spectrum fit by GUAPX. This method is applied to MSL spectra with long integration duration (greater than 3 hours) and with energy resolution less than 180 eV at 5.9 keV. These overnight spectra encompass a variety of geologic materials examined by the Curiosity Rover, including volcanic and sedimentary lithologies. Transfer of the K-value calibration produced in the lab to the flight APXS has been completed and temperature, geometry and spectrum duration effects have been thoroughly examined. A typical limit of detection of ALICs is around 5 wt% with uncertainties of approximately 5 wt%. Accurate elemental concentrations are required as input to the Monte Carlo program (Mallet et al, 2006; Lee, 2010). Elemental concentrations are obtained from the GUAPX code using the same long duration, good resolution spectra used for determining the experimental C/R ratios (Campbell et al. 2012). Special attention was given to the assessment of Rb, Sr, and Y as these element peaks overlap the scatter peaks. Mineral effects, supported by CheMin results (Blake et al, 2013), as well as accurate geometry and environmental conditions are also considered for producing the best bulk chemistry, despite complications inherent to surface dust on unbrushed rock surfaces. The calculation of ALICs by the MSL APXS is a useful tool for producing in-situ values for volatile elements and provides an intermediate connection between the sub millimeter cubed scale of possible hydrogen concentrations found by ChemCam and the meter cubed hydrogen signature detected by DAN. These values also provide useful constraints on the absolute volatile concentrations found by SAM. MSL ALIC results are compared to previous results obtained for the 'dry' soils collected by the APXS on the MER rovers and provide a unique comparison of Martian samples from distinct locations on Mars. Results of MSL APXS data, including comparison with previous rover APXS analyses and complementary data from Curiosity's other instruments, will be presented.

Perrett, G. M.; Pradler, I.; Campbell, J. L.; Gellert, R.; Leshin, L. A.; Schmidt, M. E.; Team, M.

2013-12-01

91

Disequilibrium partial melting model and its implications for trace element fractionations during mantle melting  

NASA Astrophysics Data System (ADS)

A model to describe trace element evolutions during partial melting is proposed by assuming surface equilibrium instead of complete equilibrium between mineral grains and melt and by considering the following factors: (1) chemical diffusion in minerals; (2) melting and melt extraction. For mantle melting rates of ˜ 10-7 yr-1, inferred from mid-ocean ridge spreading rates, elements with diffusivities (D) in minerals of > 10-15 cm2/s be at equilibrium between minerals of 0.5 cm in diameter and melt during mantle melting. However, the anomalous radioactive excess of 236Ra over 230Th (up to 300%) in young basalts which cannot be explained by equilibrium melting because of the highly incompatible nature of both elements can be accounted for by the present model only when melting rate is in the orders of 10-6 to 10-5 yr-1. The disequilibrium effect cannot be ignored for elements with D < 10-13 cm2/s if the melting rate is 10-5 yr-1. Disequilibrium melting lowers the incompatibility of an incompatible element; the high the incompatibility, the more obvious this effect is. Fractionation of trace elements during disequilibrium melting depends both on their equilibrium partition coefficients (k) and their diffusivities. This has two consequences: (1) fractionation of two highly incompatible elements (k ? 0.01) by more than 20% is still possible at melting degree as high as 15% if their diffusivities differ by a factor of 5 or more, as compared to the requirement for less than 5% partial melting for the same extent of fractionation by equilibrium melting; and (2) the incompatibility order of two incompatible elements can be reversed under certain circumstances (i.e., k1 >k2, but D1 >D2). The Pb paradox, namely, that the U/Pb ratio in mantle sources inferred from Pb isotopes has increased during the differentiation of the Earth even though Pb is less incompatible than U, is explainable if the diffusivity of Pb is higher than that of U (e.g., by a factor of 10) and if the melting rate is in the order of 10-5 yr-1.

Qin, Zhenwei

1992-08-01

92

Standard reference water samples for rare earth element determinations  

USGS Publications Warehouse

Standard reference water samples (SRWS) were collected from two mine sites, one near Ophir, CO, USA and the other near Redding, CA, USA. The samples were filtered, preserved, and analyzed for rare earth element (REE) concentrations (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) by inductively coupled plasma-mass spectrometry (ICP-MS). These two samples were acid mine waters with elevated concentrations of REEs (0.45-161 ??g/1). Seventeen international laboratories participated in a 'round-robin' chemical analysis program, which made it possible to evaluate the data by robust statistical procedures that are insensitive to outliers. The resulting most probable values are reported. Ten to 15 of the participants also reported values for Ba, Y, and Sc. Field parameters, major ion, and other trace element concentrations, not subject to statistical evaluation, are provided.

Verplanck, P. L.; Antweiler, R. C.; Nordstrom, D. K.; Taylor, H. E.

2001-01-01

93

Magnetic property improvement of niobium doped with rare earth elements  

NASA Astrophysics Data System (ADS)

A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

Jiang, Tao; He, Fei-Si; Jiao, Fei; He, Fa; Lu, Xiang-Yang; Zhao, Kui; Zhao, Hong-Yun; You, Yu-Song; Chen, Lin

2014-05-01

94

Distribution of rare earth elements and uranium in various components of ordinary chondrites  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) and uranium were studied for their distributions in various component phases of four ordinary chondrites. Kesen (H4), Richardton (H5), Bruderheim (L6), and Saint Severin (LL6). A selective dissolution method was applied for the phase fractionation. The REE were analysed by neutron activation analysis, and U was determined by neutron-induced fission tracks. The present study revealed that both REE and U are highly enriched in the Ca-phosphate minerals with different enrichment factors, implying chemical fractionation between them. The phosphates seem to be responsible for more than 80 percent of the light REE in all chondrites. On the other hand, only 20-40 percent of the total U resides in the Ca-phosphates. This difference in enrichments might have been caused through the levels of metamorphic activity on the meteoritic parent bodies.

Ebihara, M.; Honda, M.

1984-06-01

95

COLORS OF A SECOND EARTH: ESTIMATING THE FRACTIONAL AREAS OF OCEAN, LAND, AND VEGETATION OF EARTH-LIKE EXOPLANETS  

SciTech Connect

Characterizing the surfaces of rocky exoplanets via their scattered light will be an essential challenge in investigating their habitability and the possible existence of life on their surfaces. We present a reconstruction method for fractional areas of different surface types from the colors of an Earth-like exoplanet. We create mock light curves for Earth without clouds using empirical data. These light curves are fitted to an isotropic scattering model consisting of four surface types: ocean, soil, snow, and vegetation. In an idealized situation where the photometric errors are only photon shot noise, we are able to reproduce the fractional areas of those components fairly well. The results offer some hope for detection of vegetation via the distinct spectral feature of photosynthesis on Earth, known as the red edge. In our reconstruction method, Rayleigh scattering due to the atmosphere plays an important role, and for terrestrial exoplanets with an atmosphere similar to our Earth, it is possible to estimate the presence of oceans and an atmosphere simultaneously.

Fujii, Yuka; Kawahara, Hajime; Suto, Yasushi; Taruya, Atsushi [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Fukuda, Satoru; Nakajima, Teruyuki [Center of Climate System Research, University of Tokyo, Kashiwa 277-8568 (Japan); Turner, Edwin L., E-mail: yuka.fujii@utap.phys.s.u-tokyo.ac.j [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2010-06-01

96

The Significance of Rare Earth Element Partition Coefficients in Zircon  

NASA Astrophysics Data System (ADS)

Over the past twenty years, there have been several studies published that used natural and synthetic samples to determine rare earth element (REE) partition coefficients for zircon in geological systems. As expected from crystal-chemical considerations, results obtained from these studies revealed that heavy REE (HREE) are more compatible than light REE (LREE) in zircon. This trend is caused primarily by decreasing ionic radii of trivalent REE from La to Lu as they approach ionic radius of Zr in zircon. When plotted against ionic radius, empirical curves through published partition coefficients of trivalent REE in zircon are convex upward, showing degrees of flatness for LREE. The strain-elasticity model for mineral-melt partition coefficients proposed by Blundy and Wood (1994) assumes that the primary factor influencing elemental partitioning into a mineral is the strain caused by substituting a trace element into a structural site. In order to estimate the three parameters Ro [optimum radius of the lattice site], Do [(theoretical) strain-free partition coefficient], and E [YoungIs Modulus], we applied a least-squares fit of empirical REE partitioning data for synthetic zircon (Hanchar et al., 2001) to the Blundy and Wood theoretical model. We then used Ro, Do and E, as determined above using the synthetic zircon data, to constrain the fit of the Blundy and Wood model to other published partition coefficients for natural and synthetic zircon. We also used a least-squares fit to published REE partitioning data for zircon without constraining the values of Ro, Do and E, in order to evaluate the extent to which published partitioning coefficients agree with the Blundy and Wood model. Most data that we fit without constraint to the Blundy and Wood model deviate significantly from partition coefficients predicted by the Blundy and Wood model, which may reflect analytical problems or mineral inclusions (e.g., monazite). Data with which the Blundy and Wood model agrees best are those reported by Sano et al. (2001) for an ion-probe study of REE partitioning between silicate glass, zircon and apatite. Furthermore, the Blundy and Wood model fits the data of Sano et al., best if Ro, Do, and E are first determined by using data reported by Hanchar et al. (2001). References Blundy, J., and Wood, B. (1994) Prediction of crystal-melt partition coefficients from elastic moduli. Nature, 372, 452-454. Hanchar, J.M., Finch, R.J., Hoskin, P.W.O., Watson, E.B., Cherniak, D.J., and Mariano, A.N. (2001) Rare earth elements in synthetic zircon. 1. Synthesis and rare earth element and phosphorus doping. American Mineralogist 86: 667-680. Sano, Y., Terada, K., Fukuoka, T. (2001) Ion microprobe analysis of rare earth elements in silicate glass, apatite, and zircon. Eleventh Annual V.M. Goldschmidt Conference, Abstract # 3310, LPI Contribution No. 1088, Lunar and Planetary Institute, Houston (CD-ROM).

Hanchar, J. M.; van Westrenen, W.; Finch, R. J.

2002-05-01

97

Isotopic fractionation of the major elements of molten basalt by chemical and thermal diffusion  

Microsoft Academic Search

Samples produced in piston cylinder experiments were used to document the thermal isotopic fractionation of all the major elements of basalt except for aluminum and the fractionation of iron isotopes by chemical diffusion between a natural basalt and rhyolite. The thermal isotopic fractionations are summarized in terms of a parameter ?i defined as the fractionation in per mil per 100°C

Frank M. Richter; E. Bruce Watson; Ruslan Mendybaev; Nicolas Dauphas; Bastian Georg; James Watkins; John Valley

2009-01-01

98

Trace Element Distributions In San Diego Bay: Copper, zinc, manganese, and the rare earth elements  

NASA Astrophysics Data System (ADS)

San Diego Bay is characterized by the occurrence of large concentration increases in copper and zinc, often related to the inputs of ships in this important harbor (Katz, 1998; Zirino et al, 1978, 1998; Esser and Volpe, 2002). In this paper we report the first data on the distribution of rare earth elements (REE) in the waters of San Diego Bay. The combination of the rare earths data set as well as the other trace element distributions allow us to determine the importance of sediment recycling on trace metals in the Bay. The data suggest that remobilization of trace metals at or near the sediment water interface is of importance (Leather et al., 1995; Chadwick, personal communication). Relevant data from both sedimentary pore fluids and benthic flux measurements that support these interpretations will also be shown.

Gieskes, J. M.; Mahn, C. L.; Rivera-Duarte, I.; Chadwick, B.

2002-12-01

99

Rare earth elements in the phosphatic-enriched sediment of the Peru shelf  

USGS Publications Warehouse

Apatite-enriched materials from the Peru shelf have been analyzed for their major oxide and rare earth element (REE) concentrations. The samples consist of (1) the fine fraction of sediment, mostly clay material, (2) phosphatic pellets and fish debris, which are dispersed throughout the fine-grained sediment, (3) tabular-shaped phosphatic crusts, which occur within the uppermost few centimeters of sediment, and (4) phosphatic nodules, which occur on the seafloor. The bulk REE concentrations of the concretions suggest that these elements are partitioned between the enclosed detrital material and the apatite fraction. Analysis of the fine-grained sediment with which the samples are associated suggested that this detrital fraction in the concretions should have shale REE values; the analysis of the fish debris suggested that the apatite fraction might have seawater values. The seawater contribution of REE's is negligible in the nodules and crust, in which the apatite occurs as a fine-grained interstitial cement. That is, the concentration of REE's and the REE patterns are predominantly a function of the amount of enclosed fine-grained sediment. By contrast, the REE pattern of the pelletal apatite suggests a seawater source and the absolute REE concentrations are relatively high. The REE P2O5 ratios of the apatite fraction of these samples thus vary from approximately zero (in the case of the crust and nodules) to as much as approximately 1.2 ?? 10-3 (in the case of the pellets). The range of this ratio suggests that rather subtle variations in the depositional environment might cause a significant variation in the REE content of this authigenic fraction of the sediment. Pelletal glauconite was also recovered from one sediment core. Its REE concentrations closely resemble those of the fish debris. ?? 1988.

Piper, D. Z.; Baedecker, P. A.; Crock, J. G.; Burnett, W. C.; Loebner, B. J.

1988-01-01

100

Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon  

NASA Technical Reports Server (NTRS)

Depletions of siderophile elements in mantles have placed constraints on the conditions on core segregation and differentiation in bodies such as Earth, Earth's Moon, Mars, and asteroid 4 Vesta. Among the siderophile elements there are a sub-set that are also volatile (volatile siderophile elements or VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd), and thus can help to constrain the origin of volatile elements in these bodies, and in particular the Earth and Moon. One of the fundamental observations of the geochemistry of the Moon is the overall depletion of volatile elements relative to the Earth, but a satisfactory explanation has remained elusive. Hypotheses for Earth include addition during accretion and core formation and mobilized into the metallic core, multiple stage origin, or addition after the core formed. Any explanation for volatile elements in the Earth's mantle must also be linked to an explanation of these elements in the lunar mantle. New metal-silicate partitioning data will be applied to the origin of volatile elements in both the Earth and Moon, and will evaluate theories for exogenous versus endogenous origin of volatile elements.

Righter, K.; Pando, K.; Danielson, L.; Nickodem, K.

2014-01-01

101

Ternary phosphates of rubidium-cesium-rare earth element  

SciTech Connect

This article examines the possibility of the existence of ternary phosphates of the rare earth elements (REE) containing two large alkali cations in order to establish the morphological and physicochemical characteristics in the entire group of ternary REE phosphates. The synthesis of the ternary rubidium-cesium-REE phosphates was carried out with molten charges that did not contain an excess of components. Analysis for the uncommon alkali cations was done by the atomic absorption technique; for holmium, by complexometric titration; and for phosphorus, by gravimetry as NH/sub 4/CdPO/sub 4/. The data obtained fully confirm the composition of Rb/sub 2/CsLn(PO/sub 4/)/sub 2/.

Mel'nikov, P.P.; Carrillo-Eredero, H.D.; Efremov, V.A.; Komissarova, L.N.; Quiroga, E.

1986-06-01

102

Use of Rare Earth Elements in Investigations of Aeolian Processes  

NASA Astrophysics Data System (ADS)

Aeolian movement of surface sediments is a natural geomorphic process that has shaped landscapes and contributes to atmospheric dust loading. Even on seemingly uniform surfaces, aeolian activity is highly variable in space and time. Tagging individual particles with Rare Earth Elements (REE) that are present in only trace amounts in the native surface soils allows the study of aeolian transport from source to sink. Rare Earth Oxides are dissolved in nitric acid and diluted to provide a several order of magnitude increase in soil REE concentration when sprayed on the source soil and allowed to infiltrate to a shallow depth. A single REE may be applied to a small area of the surface or multiple REEs may be applied to discrete micro-sites on the surface. The sediments trapped by standard aeolian samplers record the relative contributions of the tagged areas and the dispersal from a point source. We have successfully used REEs to investigate preferential micro-sites for post-fire aeolian activity in a heterogeneous environment and to investigate single season aeolian dispersal from a point source. We are also collaborating with others on the use of REEs to quantify the development of nutrient islands in desert shrublands.

Van Pelt, R. S.; Barnes, M. A.; Zobeck, T. M.

2012-12-01

103

Rare Earth elements in individual minerals in Shergottites  

NASA Technical Reports Server (NTRS)

Shergottites (i.e., Shergotty, Zagami, EETA79001, ALHA77005, and LEW88516) are an important set of achondrites because they comprise the majority of the SNC group of meteorites (nine, in total, known to us), which are likely to be samples of the planet Mars. Study of these meteorites may therefore provide valuable information about petrogenetic processes on a large planetary body other than Earth. Rare earth element (REE) distributions between various mineral phases were found to be useful in geochemically modeling the petrogenesis of various rock types (terrestrial and meteoritic). However, with the exception of a few ion microprobe studies and analyses of mineral separates, there has previously not been any comprehensive effort to characterize and directly compare REE in individual minerals in each of the five known shergottites. Ion microprobe analyses were made on thin sections of each of the shergottites. Minerals analyzed were pyroxenes (pigeonite and augite), maskelynite, and whitlockite. The REE concentrations in each mineral type in each shergottite is given.

Wadhwa, Meenakshi; Crozaz, Ghislaine

1993-01-01

104

Speciation and Fractionation of Elements in Tea Infusions  

Microsoft Academic Search

Elements in tea infusions may be present in the form of various species with different mobility, availability, and biological activity. As a result, actual impact of the consumption of this beverage on human health cannot be anticipated on the basis of measurements of total concentrations of elements. Nevertheless, this type of the elemental analysis is generally found in the relevant

Maja Welna; Anna Szymczycha-Madeja; Ewelina Stelmach; Pawel Pohl

2012-01-01

105

Pb and rare earth element diffusion in xenotime  

NASA Astrophysics Data System (ADS)

Diffusion of Pb and the rare earth elements Sm, Dy and Yb have been characterized in synthetic xenotime under dry conditions. The synthetic xenotime was grown via a Na 2CO 3-MoO 3 flux method. The sources of diffusant for the rare earth diffusion experiments were REE phosphate powders, with experiments run using sources containing a single REE. For Pb, the source consisted a mixture of YPO 4 and PbTiO 3. Experiments were performed by placing source and xenotime in Pt capsules, and annealing capsules in 1 atm furnaces for times ranging from 30 min to several weeks, at temperatures from 1000 to 1500 °C. The REE and Pb distributions in the xenotime were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relations are obtained for diffusion in xenotime, normal to (101): D=1.5×10exp?(-441±12 kJmol/R?T)ms.D=9.0×10exp?(-349±16 kJmol/R?T)ms.D=3.9×10exp?(-362±13 kJmol/R?T)ms. Diffusivities among the REE do not differ greatly in xenotime over the investigated temperature range, in contrast to findings for the REE in zircon [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare earth diffusion in zircon. Chem. Geol. 134, 289-301.], where the LREE diffuse more slowly, and with higher activation energies for diffusion, than the heavier rare earths. In zircon, these differences among diffusion of the rare earths are attributed to the relatively large size of the REE with respect to Zr, for which they likely substitute in the zircon lattice. With the systematic increase in ionic radius from the heavy to lighter REE, this size mismatch becomes more pronounced and diffusivities of the LREE are as consequence slower. Although xenotime is isostructural with zircon, the REE are more closely matched in size to Y, so in xenotime this effect appears much smaller and the REE diffuse at similar rates. In addition, the process of diffusion in xenotime likely involves simple REE + 3 ? Y + 3 exchange, without charge compensation as needed for REE + 3 ? Zr + 4 exchange in zircon. This latter factor may also contribute to the large activation energies for diffusion of the REE in zircon (i.e., 691-841 kJ mol - 1 , [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare earth diffusion in zircon. Chem. Geol. 134, 289-301.]), in comparison with those for xenotime. For Pb, the following Arrhenius relation is obtained (also normal to (101)): D=3.0×10exp?(-382±64 kJmol/R?T)ms. These measurements suggest that Pb diffusion in xenotime is quite slow, even slower than Pb diffusion in monazite and zircon, and considerably slower than diffusion of the REE in xenotime. Xenotime may therefore be even more retentive of Pb isotope signatures than either monazite or zircon in cases where Pb isotopes are altered solely by volume diffusion. However, because the activation energy for Pb diffusion in xenotime is lower than those for monazite and zircon, Pb diffusion may be somewhat faster at many temperatures of geologic interest in xenotime than in monazite or zircon.

Cherniak, D. J.

2006-05-01

106

Ablative and transport fractionation of trace elements during laser sampling of glass and copper  

Microsoft Academic Search

The fractionation of trace elements due to ablation and transport processes was quantified during Q-switched infrared laser sampling of glass and copper reference materials. Filter-trapping of the ablated product at different points in the sample introduction system showed ablation and transport sometimes caused opposing fractionation effects, leading to a confounded measure of overall (ablative + transport) fractionation. An unexpected result

P. M. Outridge; W. Doherty; D. C. Gregoire

1997-01-01

107

Determination of rare-earth elements in a limestone geological standard reference material by ICP-MS following solvent extraction.  

PubMed

Rare-earth elements in a limestone geological standard (JLs-1) were determined by inductively coupled plasma mass spectroscopy (ICP-MS) using phosphoric acid 2-ethylhexyl ester solvent extraction, which had been established for seawater analysis. First, the limestone sample was divided into two fractions: acetic acid soluble (carbonate fraction) and insoluble (residue). A modification of the method was undertaken to achieve quantitative recovery. With this method most of the REEs in the carbonate fraction were quantitatively recovered, except for the heaviest three REEs (Tm, Tb and Lu). The reason for the poor recoveries of the three elements was investigated, but still remained unclear. The mass-spectroscopic interference of BaO with Eu made an accurate determination of both lighter REEs and Eu at the same time impossible. The precision of this method was better than 20%. The data adopted after analytical consideration were consistent with those previously reported. PMID:12675356

Igarashi, Kengo; Akagi, Tasuku; Fu, Feng-Fu; Yabuki, Sadayo

2003-03-01

108

Rare earth element components in atmospheric particulates in the Bayan Obo mine region.  

PubMed

The Bayan Obo mine, located in Inner Mongolia, China, is the largest light rare earth body ever found in the world. The research for rare earth elements (REEs) enrichment in atmospheric particulates caused by mining and ore processing is fairly limited so far. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 ?m (PM10) were collected around the Bayan Obo mine region, in August 2012 and March 2013, to analyze the levels and distributions of REEs in particles. The total concentrations of REEs for TSP were 149.8 and 239.6 ng/m(3), and those for PM10 were 42.8 and 68.9 ng/m(3), in August 2012 and March 2013, respectively. Enrichment factor was calculated for all 14 REEs in the TSP and PM10 and the results indicated that REEs enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in springtime. The spatial distribution of REEs in TSP showed a strong gradient concentration in the prevailing wind direction. REE chondrite normalized patterns of TSP and PM10 were similar and the normalized curves inclined to the right side, showing the conspicuous fractionation between the light REEs and heavy REE, which supported by the chondrite normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N), Gd(N)/Yb(N)). PMID:24657942

Wang, Lingqing; Liang, Tao; Zhang, Qian; Li, Kexin

2014-05-01

109

Geochemical behavior of rare earth elements and other trace elements in the Amazon River  

NASA Astrophysics Data System (ADS)

Rivers transport large amounts of dissolved and suspended particulate material from the catchment area to the oceans and are a major source of trace metals to seawater. The Amazon River is the world's largest river and supplies approximately 20% of the oceans' freshwater (Molinier et al., 1997). However, the behavior of trace elements, especially particle-reactive elements such as the rare earth elements (REE), within the river as well as in the estuary is not well constrained and rather little is known about their transport mechanisms. This study aims at understanding the transport properties of particle-reactive elements in the Amazon River and some of its major tributaries, including the Rio Solimões, Rio Negro, Tapajos, Xingu and Jari Rivers. Samples were taken at 12 stations, seven of which were located in the Amazon mainstream, while the other five stations sampled its tributaries. To account for the effects of variable discharge, the samples were collected during periods of high and low discharge. We present data for major and trace elements, including REE, of the dissolved and suspended load of these samples. First results indicate that the shale-normalized REE pattern of the dissolved load (filtered through 0.2 µm membranes) of the Amazon mainstream and the Rio Solimões confirm earlier studies (Elderfield et al., 1990; Gerard et al., 2003) and show an enrichment of the middle REE relative to the light and heavy REE (LaSN/GdSN: 0.25 - 0.32; GdSN/YbSN: 1.54 - 1.78). In contrast to the Amazon mainstream and the Rio Solimões, which are considered to be whitewater rivers, blackwater rivers, such as the Rio Negro, have a flat REE pattern with higher REE concentrations than whitewater rivers. The third water-type found in the Amazon Basin is clearwater, e.g. Rio Tapajos, with REE patterns in between those of the other two types, i.e. LaSN/GdSN: 0.55 - 0.70; GdSN/YbSN: 1.26 - 1.55. A similar behavior can be identified for other major and trace elements. While elements such as Ca, Mg, Sr or U are relatively high in whitewater rivers, their concentrations are generally lower in clearwater rivers and lowest in blackwater rivers. In contrast, elements including Si, Rb and Cs have their highest concentrations in blackwater rivers, intermediate concentrations in clearwater rivers and their lowest concentrations in whitewater river. [1] Elderfield H., Upstill-Goddard R. and Sholkovitz E.R. (1990): The rare earth elements in rivers, estuaries and coastal seas and their significance to the composition of ocean waters. Geochim.Cosmochim.Acta, 54, 971-991 [2] Gerard M., Seyler P., Benedetti M.F., Alves V.P., Boaventura G.R. and Sondag, F. (2003): Rare earth elements in the Amazon basin. Hydrological Processes, 17, 1379-1392 [3] Molinier M., Guyot J.L., Callede J., Guimaraes V., Oliveira E. and Filizola N. (1997): Hydrologie du bassinamazonien. Evironment et développement en Amazonie brésiliènne, Thery H. (ed.), Berlin Publ., Paris; 24-41

Merschel, Gila; Bau, Michael; Dantas, Elton Luiz

2014-05-01

110

Spectroscopy of Luminescent Crystals Containing Rare Earth Elements  

NASA Astrophysics Data System (ADS)

We have studied the spectroscopy of luminescent crystals containing rare earth elements such as KEuGe_2O_6, Cs_3EuSi_6O_{15}, K_4[(UO_2)Eu_2(Ge_2O_7)_2], and R_2(C_8H_{10}O_4)_3 (R= Y, Tb, or Eu). The emission and excitation spectra of these compounds were recorded at ambient temperature. These spectra are consistent with the structures which were determined by single crystal X-ray diffraction. Crystals containing hybrid luminescent centers were also synthesized and interesting energy transfer mechanisms were observed. For example, dramatic luminescence quenching was found in KEu_xNd_{1-x}Ge_2O_6 (x= 0.98, 0.96, 0.94, and 0.84) as well as in Cs_3Eu_{0.98}Nd_{0.02}Si_6O_{15}, while different compositions of Y_xEu_yTb_{2-x-y}(C_8H_{10}O_4)_3 exhibit different emission colors. Emission lifetimes were also measured for these compounds, and the results shed light on the energy transfer mechanisms. Detailed results of our research will be presented. P.-L. Chen, P.-Y. Chiang, H.-C. Yeh, B.-C. Chang, and K.-H. Lii, Dalton Trans., 1721 (2008). M.-Y. Hung, Y.-H. Chen, B.-C. Chang, and K.-H. Lii, Chem. Mater. 17, 5743 (2005).

Chen, Meng-Ling; Lii, Kwang-Hwa; Chang, Bor-Chen

2013-06-01

111

Effect of Rare Earth Elements on Isothermal Transformation and Microstructures in 20Mn Steel.  

National Technical Information Service (NTIS)

The effect of rare earth elements on the isothermal transformation and microstructures in 20Mn steel is investigated by means of metallography and dilatometry. Rare earth elements decrease both the incubation period of pro-eutectoid ferrite and the rate o...

H. Liu D. H. Zheng Z. Y. Xu T. Y. Hsu

1995-01-01

112

Preliminary Assessment of Rare Earth Element Contents of Niger Delta Oils  

Microsoft Academic Search

A preliminary study of the rare earth element contents of some Niger Delta oils was carried out to evaluate their influence on petroleum system of the Niger Delta Basin. The oil samples were obtained from an onshore field in the Niger Delta and analyzed using Inductively Coupled Plasma Mass Spectrometric (ICP-MS) analytical technique. Four Light Rare Earth Elements (LREE), La,

A. Akinlua; T. R. Ajayi; B. B. Adeleke

2006-01-01

113

Presolar SiC Grains and Rare Earth Element Production in AGB Stars  

Microsoft Academic Search

The relative abundances of many isotopes of the rare earth elements are strongly affected by s-process nucleosynthesis in low-mass asymptotic giant branch (AGB) stars. We briefly explore the nucleosynthesis of the rare earth elements in AGB stars and their implications for measurements of presolar SiC grains from those stars.

Andrew M. Davis; Roberto Gallino

2008-01-01

114

Special glassy materials doped with rare-earth elements for fiber optics  

Microsoft Academic Search

Lead-bismuth-gallium-cadmium glasses doped with rare earths elements have been investigated. Certain optical properties of the glasses have been determined. The results of luminescence investiations in the form of absorption and luminescence spectra are presented, and the quantum yields as well as the calculated and measured luminescence lifetimes of the particular rare earths elements in the matrix of the examined glasses

Jan Wasylak; Dominik Dorosz; Jan Kucharski; Jan Kityk

2003-01-01

115

Light elements in the Earth's core: Fe3X compounds  

NASA Astrophysics Data System (ADS)

The nature of the light element (or elements) of the core has been the subject of considerable speculation, because of its bearing on the overall bulk composition of the earth, the conditions under which the core formed, the temperature regime in the core and the continuing process of core-mantle reaction. The correct thermodynamical and thermochemical properties of iron alloyed with any of the potential major candidate light elements - sulfur, carbon and silicon - are described along solid solutions. At least at low pressures, one of their major eutectic points is found at Fe3X compositions. Here we study in detail the compressibility and elasticity of these phases, Fe3S, Fe3C and Fe3Si, up to inner core pressures. For this specific stoichiometry Fe - Me = 3 - 1, both the sulfide and the carbide present the cementite orthorhombic structure up to inner core pressures. They exhibit a gradual decrease of the residual magnetic moment, in ferromagnetic configuration. The spin transition occurs largely below the core conditions. The silicide behaves differently. Fe3Si is not stable as cementite and during the relaxation the structure naturally evolves into a standard face-centered cubic structure, where Si occupies every fourth site. The structure is ferromagnetic with non-vanishing spin even at inner core pressures. The density of all Fe3X compounds analyzed here is smaller than that of hexagonally-close packed (hcp) iron by about 10-15%. Fe3S and Fe3C have similar values of bulk modulus as hcp iron and show smaller values for the shear modulus. Fe3Si shows considerably smaller values for both elastic moduli. In terms of velocities, Fe3S presents the closest velocities to hcp iron from all the three Fe3X candidates in terms of both Vp and Vs. Fe3Si shows larger Vp than hcp iron by about 4%. The difference in Vs is on the order of 11%. Fe3C shows the largest difference. Both Vp and Vs of Fe3C are considerably smaller than of pure iron. However adding carbon to iron is not enough to decrease its velocities enough to match PREM, even if we consider a thermal correction of 5%.

Calderon, A. V.; Caracas, R.; Romero, A. H.

2010-12-01

116

The geochemistry of rare earth elements in the Amazon River estuary  

SciTech Connect

The estuarine geochemistry of rare earth elements (REEs) was studied using samples collected in the Amazon River estuary from the AmasSeds (Amazon Shelf SEDiment Study) cruise of August 1989. Extensive removal of dissolved (0.22 [mu]m filtered) trivalent REEs from river water occurs in the low (0--6) salinity region. Removal by the salt-induced coagulation of river colloids leads to fractionation among the REE(III) series; the order of removal is light REEs > middle REEs > heavy REEs. There also is the enhanced removal of Ce (relative to trivalent La and Nd) in the low salinity (0--6) zone and in the zone of high biological activity. This is the first field observation of strong Ce removal associated with coagulation of river colloids and biological productivity. The argument is made that the decrease in the Ce anomaly across a biological front is caused by biologically mediated oxidation of Ce(III) to Ce(IV). Coagulation of river colloids and biologically mediated oxidation of Ce(III) lead to fractionation of REE(III) and redox modification of Ce. These processes result in the REE composition becoming fractionated relative to the Amazon River water and crust and more evolved toward the REE composition of the oceans. This study implies that reactions in estuaries play significant, yet poorly understood roles in controlling the REE composition and Ce anomaly of the oceans. 46 refs., 9 figs., 2 tabs.

Shokovitz, E.R. (Woods Hole Oceanographic Institution, MA (United States))

1993-05-01

117

Carbonatite and alkaline intrusion-related rare earth element deposits–A deposit model  

USGS Publications Warehouse

The rare earth elements are not as rare in nature as their name implies, but economic deposits with these elements are not common and few deposits have been large producers. In the past 25 years, demand for rare earth elements has increased dramatically because of their wide and diverse use in high-technology applications. Yet, presently the global production and supply of rare earth elements come from only a few sources. China produces more than 95 percent of the world's supply of rare earth elements. Because of China's decision to restrict exports of these elements, the price of rare earth elements has increased and industrial countries are concerned about supply shortages. As a result, understanding the distribution and origin of rare earth elements deposits, and identifying and quantifying our nation's rare earth elements resources have become priorities. Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. The general mineral deposit model summarized here is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. Carbonatite and alkaline intrusion-related REE deposits are discussed together because of their spatial association, common enrichment in incompatible elements, and similarities in genesis. A wide variety of commodities have been exploited from carbonatites and alkaline igneous rocks, such as rare earth elements, niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other enrichments include manganese, strontium, tantalum, thorium, vanadium, and uranium.

Verplanck, Philip L.; Van Gosen, Bradley S.

2011-01-01

118

Skeleton versus fine earth: what information is stored in the mobile extracellular soil DNA fraction?  

NASA Astrophysics Data System (ADS)

The soil genome consists of an intracellular and an extracellular fraction. Recently, soil extracellular DNA (eDNA) has been shown to be quantitatively relevant, with a high survival capacity and mobility, playing a crucial role in the gene transfer by transformation, in the formation of bacterial biofilm and as a source of nutrients for soil microorganisms. The eDNA fraction can be discriminated and classified by its interaction with clay minerals, humic acids and Al/Fe oxihydroxides, resulting in differently mobile components. The eDNA extractable in water, classified as DNA free in the extracellular soil environment or adsorbed on soil colloids (eDNAfree/adsorbed), is hypothesized to be the most mobile DNA in soil. Challenging to assess the information stored in this DNA fraction, eDNAfree/adsorbed was recovered from fine earth (< 4 mm) and highly altered rock fragments or skeleton (4-10 mm) of six consecutive horizons (A1-BCb2) of a forest soil profile by washing the two soil fractions with H2O. Quantitative analysis have been conducted in terms of DNA yields (fluorimeter and spectrophotometer), molecular weight and fragment length distribution (gel electrophoresis), and qualitative analysis in terms of the composition and distribution of fungal and bacterial communities (Denaturing Gradient Gel Electrophoresis- fingerprinting). The mobile soil eDNA, extracted from each horizon, was characterised by low molecular weight (< 2 kb) and amounts ranging from 3.96 (±0.179) to 0.17 (±0.023) µg g-1 for the fine earth and from 1.42 (±0.111) to 0.11 (±0.007) µg g-1 for the skeleton. Genetic fingerprinting of eDNA recovered from fine earth and skeleton revealed characteristic fungal and bacterial communities of each horizon, but also similarities among the microbial communities of both soil fractions and horizons. This could be interpreted also as a result of the movement of eDNA along the soil profile and from fine earth to skeleton. The molecular characterization provided information about the autochthonous microflora inhabiting skeleton and fine earth as well as information about the fate of soil DNA in terms of presence, persistence and movement of eDNA and the stored genetic information.

Ascher, Judith; Ceccherini, Maria Teresa; Agnelli, Alberto; Corti, Guiseppe; Pietramellara, Giacomo

2010-05-01

119

The rare earth element geochemistry of granite, gneiss, and migmatite from the Western Metamorphic Belt of South-eastern Australia  

Microsoft Academic Search

Four muscovite-biotite granites from the Western Metamorphic Belt of South-eastern Australia have rare earth element patterns characterized by: (i) light rare earth element enrichment; (ii) slight Eu depletion; (iii) varying degrees of heavy rare earth element depletion. The rare earth element and major element chemistry of three of these muscovite-biotite granites (the Koetong, Lockharts and Yabba Granites) can be approximated

R. C. Price; S. R. Taylor

1977-01-01

120

Fractions!  

NSDL National Science Digital Library

Practice all of the activities to help you learn fractions! Go through all five levels of Fractions Review Activities Practice Naming Fractions Do you remember how to do Fraction Sets? Play these games when you have finished the top three activities: Cross the River Pizza Party Fractions Rescue Island Adding Subtracting Fractions SPLAT Mrs. Anderson's Fraction Games Action Fraction Soccer Shootout Fraction Multiplication Soccer Shootout Fraction Division Dirt Bike Fractions Comparisons ...

Lerdahl, Miss

2011-02-01

121

Element-free Galerkin (EFG) method for analysis of the time-fractional partial differential equations  

Microsoft Academic Search

The present paper deals with the numerical solution of time-fractional partial differential equations using the element-free Galerkin (EFG) method, which is based on the moving least-square approximation. Compared with numerical methods based on meshes, the EFG method for time-fractional partial differential equations needs only scattered nodes instead of meshing the domain of the problem. It neither requires element connectivity nor

Ge Hong-Xia; Liu Yong-Qing; Cheng Rong-Jun

2012-01-01

122

Review of rare earth element concentrations in oil shales of the Eocene Green River Formation  

USGS Publications Warehouse

Concentrations of the lanthanide series or rare earth elements and yttrium were determined for lacustrine oil shale samples from the Eocene Green River Formation in the Piceance Basin of Colorado and the Uinta Basin of Utah. Unprocessed oil shale, post-pyrolysis (spent) shale, and leached shale samples were examined to determine if oil-shale processing to generate oil or the remediation of retorted shale affects rare earth element concentrations. Results for unprocessed Green River oil shale samples were compared to data published in the literature on reference materials, such as chondritic meteorites, the North American shale composite, marine oil shale samples from two sites in northern Tibet, and mined rare earth element ores from the United States and China. The Green River oil shales had lower rare earth element concentrations (66.3 to 141.3 micrograms per gram, ?g g-1) than are typical of material in the upper crust (approximately 170 ?g g-1) and were also lower in rare earth elements relative to the North American shale composite (approximately 165 ?g g-1). Adjusting for dilution of rare earth elements by organic matter does not account for the total difference between the oil shales and other crustal rocks. Europium anomalies for Green River oil shales from the Piceance Basin were slightly lower than those reported for the North American shale composite and upper crust. When compared to ores currently mined for rare earth elements, the concentrations in Green River oil shales are several orders of magnitude lower. Retorting Green River oil shales led to a slight enrichment of rare earth elements due to removal of organic matter. When concentrations in spent and leached samples were normalized to an original rock basis, concentrations were comparable to those of the raw shale, indicating that rare earth elements are conserved in processed oil shales.

Birdwell, Justin E.

2012-01-01

123

Composition of the earth's upper mantle-I. Siderophile trace elements in ultramafic nodules  

USGS Publications Warehouse

Seven siderophile elements (Au, Ge, Ir, Ni, Pd, Os, Re) were determined by radiochemical neutron activation analysis in 19 ultramafic rocks, which are spinel lherzollites-xenoliths from North and Central America, Hawaii and Australia, and garnet Iherzolitexenoliths from Lesotho. Abundances of the platinum metals are very uniform in spinel lherzolites averaging 3.4 ?? 1.2 ppb Os, 3.7 ?? 1.1 ppb Ir, and 4.6 ?? 2.0 ppb Pd. Sheared garnet lherzolite PHN 1611 has similar abundances of these elements, but in 4 granulated garnet lherzolites, abundances are more variable. In all samples, the Pt metals retain cosmic ( Cl-chondrite) ratios. Abundances of Au and Re vary more than those of Pt metals, but the Au/Re ratio remains close to the cosmic value. The fact that higher values of Au and Re approach cosmic proportions with respect to the Pt metals, suggests that Au and Re have been depleted in some ultramafic rocks from an initially chondrite-like pattern equivalent to about 0.01 of Cl chondrite abundances. The relative enrichment of Au and Re in crustal rocks is apparently the result of crust-mantle fractionation and does not require a special circumstance of core-mantle partitioning. Abundances of moderately volatile elements Ni, Co and Ge are very uniform in all rocks, and are much higher than those of the highly siderophile elements Au, Ir, Pd, Os and Re. When normalized to Cl chondrites, abundances of Ni and Co are nearly identical, averaging 0.20 ?? 0.02 and 0.22 ?? 0.02, respectively; but Ge is only 0.027 ?? 0.004. The low abundance of Ge relative to Ni and Co is apparently a reflection of the general depletion of volatile elements in the Earth. The moderately siderophile elements cannot be derived from the same source as the highly siderophile elements because of the marked difference in Cl chondrite-normalized abundances and patterns. We suggest that most of the Ni, Co and Ge were enriched in the silicate by the partial oxidation of pre-existing volatile-poor Fe-Ni, whereas the corresponding highly siderophile elements remained sequestered by the surviving metal. The highly siderophile elements may have been introduced by a population of ~103 large (~1022 g) planetisimals, similar to those forming the lunar mare basins. ?? 1981.

Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

1981-01-01

124

Finite element formulation of viscoelastic sandwich beams using fractional derivative operators  

Microsoft Academic Search

This paper presents a finite element formulation for transient dynamic analysis of sandwich beams with embedded viscoelastic material using fractional derivative constitutive equations. The sandwich configuration is composed of a viscoelastic core (based on Timoshenko theory) sandwiched between elastic faces (based on Euler–Bernoulli assumptions). The viscoelastic model used to describe the behavior of the core is a four-parameter fractional derivative

A. C. Galucio; J.-F. Deü; R. Ohayon

2004-01-01

125

Finite element formulation of viscoelastic sandwich beams using fractional derivative operators  

Microsoft Academic Search

This paper presents a finite element formulation for transient dynamic analysis of sandwich beams with embedded viscoelastic material using fractional derivative constitutive equations. The sandwich configuration is composed of a viscoelastic core (based on Timoshenko theory) sandwiched between elastic faces (based on Euler-Bernoulli assumptions). The viscoelastic model used to describe the behavior of the core is a four-parameter fractional derivative

A. C. Galucio; J.-F. Deü; R. Ohayon

2004-01-01

126

Determination of element affinities by density fractionation of bulk coal samples  

USGS Publications Warehouse

A review has been made of the various methods of determining major and trace element affinities for different phases, both mineral and organic in coals, citing their various strengths and weaknesses. These include mathematical deconvolution of chemical analyses, direct microanalysis, sequential extraction procedures and density fractionation. A new methodology combining density fractionation with mathematical deconvolution of chemical analyses of whole coals and their density fractions has been evaluated. These coals formed part of the IEA-Coal Research project on the Modes of Occurrence of Trace Elements in Coal. Results were compared to a previously reported sequential extraction methodology and showed good agreement for most elements. For particular elements (Be, Mo, Cu, Se and REEs) in specific coals where disagreement was found, it was concluded that the occurrence of rare trace element bearing phases may account for the discrepancy, and modifications to the general procedure must be made to account for these.

Querol, X.; Klika, Z.; Weiss, Z.; Finkelman, R. B.; Alastuey, A.; Juan, R.; Lopez-Soler, A.; Plana, F.; Kolker, A.; Chenery, S. R. N.

2001-01-01

127

RARE EARTH ELEMENTS: A REVIEW OF PRODUCTION, PROCESSING, RECYCLING, AND ASSOCIATED ENVIRONMENTAL ISSUES  

EPA Science Inventory

Rare earth elements (REEs) are a group of 15 chemical elements in the periodic table, specifically the lanthanides. Two other elements, scandium and yttrium, have a similar physiochemistry to the lanthanides, are commonly found in the same mineral assemblages, and are often refe...

128

Elemental Fractionation During Rapid Accretion of the Moon Triggered by a Giant Impact  

NASA Technical Reports Server (NTRS)

Recently, Ida et al. made an N-body simulation of lunar accretion from a protolunar disk formed by a giant impact. One of their important conclusions is that the accretion time of the Moon is as short as one month. Such rapid accretion is a necessary consequence of the high surface density of a lunar mass disk accreting just beyond the Roche limit (about 3Re); the Safronov accretion time (a few days) is even shorter. The energy of accretion always exceeds the gravitational binding energy of newly arriving matter. Hence, without an energy sink, the accreting body is thermally unstable. For the Earth and other planets, radiation acts as the sink. However, in such a short accretion time, the Moon cannot radiate the accretional energy. Even radiating at a silicate cloudtop temperature of roughly 2000 K, it would take more than 100 yr to radiatively cool the Moon. The plausible alternative heat sinks are heat capacity, latent heat of vaporization, and thermal escape of the gas to space (i.e., hydrodynamic blowoff). The latter becomes plausible for the Moon because the scale height at 2000 K (about 300 km) is a significant fraction of the lunar radius. The early stages of lunar (or "lunatesimal") growth release relatively little energy and can occur simply by heating the material, especially if the accreting material is originally cold. However, the material is unlikely to be cold, because the disk itself is hot and cooling time is long, while the lunar accretion time iss very short. Therefore, the moon is likely to accrete condensed material just after it condenses. Accordingly, the newly accreted material will be on the verge of vaporization and will have very little heat capacity to spare. The immediate heat sink is the latent heat of vaporization. Most of the vapor will escape from the moon, because the thermal energy in the gas can be used to drive escape. However, vaporization is generally incomplete. the latent heat of vaporization exceeds the energy of accretion. Viewed globally, the accretional energy is about half the energy required to vaporize the entire Moon. Thus to first approximation, half of the Moon-forming material can be vaporized and lost during accretion. During this process, we would expect preferential loss of relatively volatile elements. Escape will retard the rate of accretion. To test these ideas, we computed detailed models of the thermal state of the Moon during accretion. We pay special attention to the structure of the silicate atmosphere and its loss rate by calculating the chemical species at equilibrium. We used the PHEQ program which includes 12 elements (H,O,C,Mg,Si,Fe,Ca, Al, Na,Ti, and N.) and 272 compounds (including ionic compounds). Because of the large heats of vaporization and ionization, the adiabatic atmosphere is nearly isothermal and massive escape is expected. The pressure of the atmosphere is determined by the balance between vaporization of a accreting material and escape. If the accretion time is one month, a 0.3 bar atmosphere is expected. Elemental fractionation depends strongly on the temperature of the accreting material. The initial temperature of the material can be estimated from the condition of gravitational instability in the protolunar disk. As shown by Ida et al, accretion starts when gravitational instability occurs when more than 99% of the material condenses. At this point, all of Ca, Al, Si, Mg, and Fe, and 95% of Na (probably K also), are in condensed phases. If the moon is formed from the accretion of such material, volatile elements such as Na, and K are retained by the moon only early in accretion. At later times, K and Na are lost and a fraction of the MG, Si and Fe is lost. However, refractory elements such as Ca and Al are retained and so achieve a mild degree (factor 2) of superabundance.

Abe, Y.; Zahnle, K. J.; Hashimoto, A.

1998-01-01

129

Rare Earth elements as sediment tracers in Mangrove ecosystems  

NASA Astrophysics Data System (ADS)

Rare earth elements have been widely used as geochemical source fingerprints of rocks and sediments to study processes involving cosmo-chemistry, igneous petrology, tectonic setting and for investigations of water-rock interactions and weathering processes including transport of weathering products to the oceans.Many studies have addressed the use of REEs in investigating the environmental impact of human activity and demonstrated that the REE natural distribution in sediment from densely industrialised and populated regions can be altered by anthropogenic influences.The coastal wetlands like Mangroves are ultimate sinks for all the material derived from the terrestrial and marine environment.The high productivity and low ratio of sediment respiration to net primary production gives mangrove sediments the potential for long-term sequestration of these pollutants/metals before reaching the coastal ocean. Geochemical study of REE in these sedimentary systems is useful for determining the nature of the biogeochemical processes. In particular, REE show a great sensitivity to pH changes, redox conditions and adsorption/ desorption reactions. So, they may be used as markers of discharge provenance, weathering processes, changes in environmental conditions in the water and sediments of Mangrove/wetland systems. Our study aims to establish the abundance, distribution and enrichment of REEs to track the sediment sources and biogeochemical processes occurring in the mangrove environment.Core sediments were collected from the different environmental settings within the Pichavaram mangrove area.Higher REE concentration in Pichavaram sediments indicated greater input from sources like terrestrial weathering and anthropogenic activities which in turn are affected by saline mixing and dynamic physico-chemical processes occurring in the mangrove environment. REE enrichment order was attributed to the alkaline pH (7-8.5) and reducing conditions prevailing in the mangrove environments leading to preferential removal of MREE and LREE by adsorption and precipitation as Fe-Mn oxy-hydroxides in sediments. PAAS normalised plots also depicted slightly convex sub-parallel shale like patterns with alike enrichment.The same characteristics have been observed for sediments for Kaveri River validating that the sediments brought down during fluvial transport, is the source of REE in Pichavaram. Strong positive Eu anomalies suggested prevalence of reducing conditions as well as it indicated source from the natural weathering of the post Archean charnockitic and gneissic terrain in the course of river Kaveri. Role of different mangroves species in controlling the REE distribution in sediments was also observed . Tidally influenced cores showed complexity of environment these sites were exposed to. Factor analysis delineated three main processes controlling REE distribution in Pichavaram, namely natural weathering, inherent physico-chemical processes and in-situ biogeochemical processes occurring in this hypersaline mangrove environment.

Ramanathan, A. L.; Swathi, S.

2013-05-01

130

State of rare earth elements in different environmental components in mining areas of China.  

PubMed

China has relatively abundant rare earth elements (REEs) reserves and will continue to be one of the major producers of REEs for the world market in the foreseeable future. However, due to the large scale of mining and refining activities, large amounts of REEs have been released to the surrounding environment and caused harmful effects on local residents. This paper summarizes the data about the contents and translocation of REEs in soils, waters, atmosphere, and plants in REE mining areas of China and discusses the characteristics of their forms, distribution, fractionation, and influencing factors. Obviously high concentrations of REEs with active and bioavailable forms are observed in all environmental media. The mobility and bioavailability of REEs are enhanced. The distribution patterns of REEs in soils and water bodies are all in line with their parent rocks. Significant fractionation phenomenon among individual members of REEs was found in soil-plant systems. However, limited knowledge was available for REEs in atmosphere. More studies focusing on the behavior of REEs in ambient air of REE mining areas in China are highly suggested. In addition, systematic study on the translocation and circulation of REEs in various media in REEs mining areas and their health risk assessment should be carried out. Standard analytical methods of REEs in environments need to be established, and more specific guideline values of REEs in foods should also be developed. PMID:24135922

Liang, Tao; Li, Kexin; Wang, Lingqing

2014-03-01

131

Elemental fractionation in ultraviolet laser ablation sampling of igneous silicate minerals relevant to Mars  

Microsoft Academic Search

Laser ablation sampling (LAS) has significant potential for remote terrestrial and extraterrestrial applications if fractionation can be understood and controlled. This study focuses on acmite, albite, augite, diopside, forsterite, and labradorite, silicate minerals that are relevant to Mars, Earth, the moon, and asteroids. The minerals were sampled using a frequency-quadrupled Nd:YAG laser and the samples were deposited as films on

M. E Taylor; D. L Blaney; G Cardell

2000-01-01

132

Trace elements in ocean ridge basalt glasses - Implications for fractionations during mantle evolution and petrogenesis  

NASA Technical Reports Server (NTRS)

Seven documented and fresh glassy selvages from ocean floor basalt pillows were analyzed for trace elements including Ag, Au, Bi, Br, Ni, Pd, and Zn using radiochemical activation analysis. Glasses from DSDP leg 24, site 238 in the Indian Ocean have a trace element pattern which reflects secondary processes at a shallow depth. Chemical fractionations in petrogenesis of tholeiitic basalts indicate that (Ir, Os), Au, Pd, Ni, and Re are strongly fractionated in igneous processes; the unfractionated chondritic mantle pattern thus imposes constraints on mantle evolution models. Finally, the limited Rb/Cs fractionation in oceanic tholeiites reflects the low abundance of volatiles and hydrous silicates in normal ocean ridge basalts.

Hertogen, J.; Janssens, M.-J.; Palme, H.

1980-01-01

133

Ligand extraction of rare earth elements from aquifer sediments: Implications for rare earth element complexation with organic matter in natural waters  

NASA Astrophysics Data System (ADS)

The ability of organic matter as well as carbonate ions to extract rare earth elements (REEs) from sandy sediments of a Coastal Plain aquifer was investigated for unpurified organic matter from different sources (i.e., Mississippi River natural organic matter, Aldrich humic acid, Nordic aquatic fulvic acid, Suwannee River fulvic acid, and Suwannee River natural organic matter) and for extraction solutions containing weak (i.e., CH 3COO -) or strong (i.e., CO32-) ligands. The experimental results indicate that, in the absence of strong REE complexing ligands in solution, the amount of REEs released from the sand is small and the fractionation pattern of the released REEs appears to be controlled by the surface stability constants for REE sorption with Fe(III) oxides/oxyhydroxides. In the presence of strong solution complexing ligands, however, the amount and the fractionation pattern of the released REEs reflect the strength and variation of the stability constants of the dominant aqueous REE species across the REE series. The varying amount of REEs extracted by the different organic matter employed in the experiments indicates that organic matter from different sources has different complexing capacity for REEs. However, the fractionation pattern of REEs extracted by the various organic matter used in our experiments is remarkable consistent, being independent of the source and the concentration of organic matter used, as well as solution pH. Because natural aquifer sand and unpurified organic matter were used in our experiments, our experimental conditions are more broadly similar to natural systems than many previous laboratory experiments of REE-humic complexation that employed purified humic substances. Our results suggest that the REE loading effect on REE-humic complexation is negligible in natural waters as more abundant metal cations (e.g., Fe, Al) out-compete REEs for strong binding sites on organic matter. More specifically, our results indicate that REE complexation with organic matter in natural waters is dominated by REE binding to weak sites on dissolved organic matter, which subsequently leads to a middle REE (MREE: Sm-Ho)-enriched fractionation pattern. The experiments also indicate that carbonate ions may effectively compete with fulvic acid in binding with dissolved REEs, but cannot out compete humic acids for REEs. Therefore, in natural waters where low molecular weight (LMW) dissolved organic carbon (DOC) is the predominant form of DOC (e.g., lower Mississippi River water), REEs occur as "truly" dissolved species by complexing with carbonate ions as well as FA, resulting in heavy REE (HREE: Er-Lu)-enriched shale-normalized fractionation patterns. Whereas, in natural terrestrial waters where REE speciation is dominated by organic complexes with high molecular weight DOC (e.g., "colloidal" HA), only MREE-enriched fractionation patterns will be observed because the more abundant, weak sites preferentially complex MREEs relative to HREEs and light REEs (LREEs: La-Nd).

Tang, Jianwu; Johannesson, Karen H.

2010-12-01

134

Precious metals and rare earth elements in municipal solid waste--sources and fate in a Swiss incineration plant.  

PubMed

In Switzerland many kinds of waste, e.g. paper, metals, electrical and electronic equipment are separately collected and recycled to a large extent. The residual amount of municipal solid waste (MSW) has to be thermally treated before final disposal. Efforts to recover valuable metals from incineration residues have recently increased. However, the resource potential of critical elements in the waste input (sources) and their partitioning into recyclable fractions and residues (fate) is unknown. Therefore, a substance flow analysis (SFA) for 31 elements including precious metals (Au, Ag), platinum metal group elements (Pt, Rh) and rare earth elements (La, Ce, etc.) has been conducted in a solid waste incinerator (SWI) with a state-of-the-art bottom ash treatment according to the Thermo-Re® concept. The SFA allowed the determination of the element partitioning in the SWI, as well as the elemental composition of the MSW by indirect analysis. The results show that the waste-input contains substantial quantities of precious metals, such as 0.4 ± 0.2mg/kg Au and 5.3 ± 0.7 mg/kg Ag. Many of the valuable substances, such as Au and Ag are enriched in specific outputs (e.g. non-ferrous metal fractions) and are therefore recoverable. As the precious metal content in MSW is expected to rise due to its increasing application in complex consumer products, the results of this study are essential for the improvement of resource recovery in the Thermo-Re® process. PMID:23085306

Morf, Leo S; Gloor, Rolf; Haag, Olaf; Haupt, Melanie; Skutan, Stefan; Di Lorenzo, Fabian; Böni, Daniel

2013-03-01

135

A deposit model for carbonatite and peralkaline intrusion-related rare earth element deposits: Chapter J in Mineral deposit models for resource assessment  

USGS Publications Warehouse

Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other elements enriched in these deposits include manganese, strontium, tantalum, thorium, vanadium, and uranium. Carbonatite and peralkaline intrusion-related rare earth element deposits are presented together in this report because of the spatial, and potentially genetic, association between carbonatite and alkaline rocks. Although these rock types occur together at many locations, carbonatite and peralkaline intrusion-related rare earth element deposits are not generally found together. Carbonatite hosted rare earth element deposits are found throughout the world, but currently only five are being mined for rare earth elements: Bayan Obo, Daluxiang, Maoniuping, and Weishan deposits in China and the Mountain Pass deposit in California, United States. These deposits are enriched in light rare earth elements, including lanthanum, cerium, praseodynium, and neodynium. The principal rare earth element-minerals associated with carbonatites are fluocarbonates (bastnäsite, parisite, and synchysite), hydrated carbonates (ancylite), and phosphates (monazite) with bastnäsite being the primary ore mineral. Calcite and dolomite are the primary gangue minerals. At present, the only rare earth element production from a peralkaline intrusion-related deposit is as a byproduct commodity at the Lovozero deposit in Russia. Important rare earth element minerals found in various deposits include apatite, eudialyte, loparite, gittinsite, xenotime, gadolinite, monazite, bastnäsite, kainosite, mosandrite, britholite, allanite, fergusonite, and zircon, and these minerals tend to be enriched in heavy rare earth elements. Carbonatite and alkaline intrusive complexes are derived from partial melts of mantle material, and neodymium isotopic data are consistent with the rare earth elements being derived from the parental magma. Deposits and these associated rock types tend to occur within stable continental tectonic units, in areas defined as shields, cratons, and crystalline blocks; they are generally associated with intracontinental rift and fault systems. Protracted fractional crystallization of the magma leads to enrichment in rare earth elements and other incompatible elements. Rare earth element mineralization associated with carbonatites can occur as either primary mineral phases or as mineralization associated with late stage orthomagmatic fluids. Rare earth element mineralization associated with alkaline intrusive complexes may occur as primary phases in magmatic layered complexes or as late-stage dikes and veins. The greatest environmental challenges associated with carbonatite and peralkaline intrusion-related rare earth element deposits center on the associated uranium and thorium. Considerable uncertainty exists around the toxicity of rare earth elements and warrants further investigation. The acid-generating potential of carbonatites and peralkaline intrusion-related deposits is low due to the dominance of carbonate minerals in carbonatite deposits, the presence of feldspars and minor calcite within the alkaline intrusion deposits, and only minor quantities of potentially acid-generating sulfides. Therefore, acid-drainage issues are not likely to be a major concern associated with these deposits. Uranium has the potential to be recovered as a byproduct, which would mitigate some of its environmental effects. However, thorium will likely remain a waste-stream product that will require management since progress is not being made towards the development of thorium-based nuclear reactors in the United States or other large scale commercial uses. Because some deposits are rich in fluorine and beryllium, these elements may be of environmental concern in certain locations.

Verplanck, Philip L.; Van Gosen, Bradley S.; Seal, Robert R.; McCafferty, Anne E.

2014-01-01

136

Fractionation of trace elements in total atmospheric deposition by filtrating-bulk passive sampling.  

PubMed

We have developed and validated a new simple and effective methodology for fractionation of soluble and insoluble forms of trace elements in total atmospheric deposition. The proposed methodology is based on the modification of a standard total deposition passive sampler by integrating a quartz fiber filter that retains the insoluble material, allowing the soluble fraction to pass through and flow to a receiving bottle. The quartz filter containing the insoluble fraction and the liquid containing the soluble fraction are then separately assayed by standardized ICP-MS protocols. The proposed atmospheric elemental fractionation sampler (AEFS) was validated by analyzing a Coal Fly Ash reference material with proper recoveries, and tested for field fractionation of a set of 10 key trace elements in total atmospheric deposition at the industrial area of Puchuncaví-Ventanas, Chile. The AEFS was proven useful for pollution assessment and also to identify variability of the soluble and insoluble fractions of the selected elements within the study area, improving the analytical information attainable by standard passive samplers for total deposition without the need of using sophisticated and high cost wet-only/dry only collectors. PMID:24840424

Rueda-Holgado, F; Palomo-Marín, M R; Calvo-Blázquez, L; Cereceda-Balic, F; Pinilla-Gil, E

2014-07-01

137

Fractional advection-dispersion equations for modeling transport at the Earth surface  

NASA Astrophysics Data System (ADS)

Characterizing the collective behavior of particle transport on the Earth surface is a key ingredient in describing landscape evolution. We seek equations that capture essential features of transport of an ensemble of particles on hillslopes, valleys, river channels, or river networks, such as mass conservation, superdiffusive spreading in flow fields with large velocity variation, or retardation due to particle trapping. Development of stochastic partial differential equations such as the advection-dispersion equation (ADE) begins with assumptions about the random behavior of a single particle: possible velocities it may experience in a flow field and the length of time it may be immobilized. When assumptions underlying the ADE are relaxed, a fractional ADE (fADE) can arise, with a non-integer-order derivative on time or space terms. Fractional ADEs are nonlocal; they describe transport affected by hydraulic conditions at a distance. Space fractional ADEs arise when velocity variations are heavy tailed and describe particle motion that accounts for variation in the flow field over the entire system. Time fractional ADEs arise as a result of power law particle residence time distributions and describe particle motion with memory in time. Here we present a phenomenological discussion of how particle transport behavior may be parsimoniously described by a fADE, consistent with evidence of superdiffusive and subdiffusive behavior in natural and experimental systems.

Schumer, Rina; Meerschaert, Mark M.; Baeumer, Boris

2009-12-01

138

Fractionation of rare-earth metallofullerenes via reversible uptake and release from reactive silica.  

PubMed

Minimal research exists for non-chromatographic separations of rare-earth metallofullerenes containing di-metallic (M2), di-metallic carbide (M2C2), and tri-metallic nitride (M3N) clusters trapped inside fullerene cages. Herein, we demonstrate a non-HPLC method (i.e., SAFA, Stir and Filter Approach) for purifying Er3N@Ih-C80, a rare-earth, metallic nitride clusterfullerene. We describe a strategic method that chemically releases rare-earth metallofullerenes (e.g., M2@C2n, M3N@C2n) trapped by aminosilica during SAFA. Recovery of metallofullerenes from spent silica represents a "green approach" because the spent silica and its useful, immobilized rare-earth metallofullerenes would have been discarded as waste material. We observe selectivity during metallofullerene uptake to aminosilica and also during its release from spent silica via addition of CS2. We describe a procedure to obtain samples enriched in M2 and M3N endohedrals. M2C2n fractions from our SAFA release process contain a wide range of higher metallofullerenes (e.g., Gd2C90-Gd2C140 or Er2C76-Er2C122). It is facile to obtain samples enriched in M3N@C82-M3N@C92. Note that unreacted M3N@C80 remains in the filtrate. The strategy for handling rare-earth metallofullerenes with different degrees of reactivity toward aminosilica is also discussed. PMID:24522624

Stevenson, Steven; Rottinger, Khristina A; Field, Jessica S

2014-05-28

139

FLUORESCENCE PROPERTIES OF As2S3 GLASS DOPED WITH RARE-EARTH ELEMENTS  

Microsoft Academic Search

Chalcogenide glasses doped with various rare-earth ions are extensively studied as potential materials for fiber optic amplifiers operating at 1.3 and 1.5 ?m telecommunication windows. The experimental results on optical absorption and photoluminescence of arsenic sulfide glasses and optical fibers doped with rare-earth elements (Pr3+, Sm3+, Er3+ and Dy3+) are presented. Near the absorption edge the rare-earth impurities affect strongly

M. Iovu; A. Andriesh; I. Culeac

140

Volatile elements in chondrites - Metamorphism or nebular fractionation  

NASA Technical Reports Server (NTRS)

Three of the most highly metamorphosed meteorites of their respective classes, Shaw (LL7), Karoonda (C5), and Coolidge (C4), were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Comparison with data by Lipschutz and coworkers (1977) on artificially heated primitive meteorites shows that the natural metamorphism of meteorites cannot have taken place in a system open to volatiles. Shaw, metamorphosed at 1300 C for more than 1 million yr, is less depleted in In, Bi, Ag, Te, Zn, and Tl than Krymka heated at 1000 C for 1 week. Karoonda, metamorphosed at 600 C for many millennia, is less depleted in Bi and Tl than Allende heated at 600 C for 1 week. Data on primordial noble gases also show that the volatile-element patterns of ordinary and carbonaceous chondrites were established by nebular condensation and changed little, if at all, during metamorphism. For enstatite chondrites, the evidence is still incomplete but seems to favor a nebular origin of the volatile pattern.

Takahashi, H.; Gros, J.; Higuchi, H.; Morgan, J. W.; Anders, E.

1978-01-01

141

Technical Information Resource on Rare Earth Elements Now Available to Public and Private Sector Stakeholders  

EPA Science Inventory

A new EPA technical information resource, ?Rare Earth Elements: A Review of Production, Processing, Recycling, and Associated Environmental Issues? has been produced as an introductory resource for those interested in learning more about REE mining and alternatives to meet demand...

142

Rare Earth Element Systematics in 48 R Chondrite Ca,Al-Rich Inclusions  

NASA Astrophysics Data System (ADS)

The compiled rare earth element systematics of 48 (including 32 new) Ca,Al-rich inclusions from seven R chondrites will be presented and implications for their formation and evolution will be discussed.

Horstmann, M.; Krause, J.; Berndt, J.; Bischoff, A.

2012-09-01

143

[Comparative study of the anticoagulant activity of dimethoxyphosphates of rare-earth elements].  

PubMed

It was shown in experiments on rabbits that dimethoxyphosphates of rare-earth elements injected intravenously displayed a marked anticoagulant activity. The highest effect was produced by compounds of neodymium, holmium, terbium, europium, thulium, dysprosium, and erbium. PMID:3758324

Novikova, N V; Lobanova, E G; Lebedeva, E N; Men'kov, A A; Galaktionova, O V

1986-01-01

144

Siderophile element fractionation in meteor crater impact glasses and metallic spherules  

NASA Technical Reports Server (NTRS)

Meteor Crater, Arizona provides an opportunity to study, in detail, elemental fractionation processes occurring during impacts through the study of target rocks, meteorite projectile and several types of impact products. We have performed EMPA and INAA on target rocks, two types of impact glass and metallic spherules from Meteor Crater. Using literature data for the well studied Canyon Diablo iron we can show that different siderophite element fractionations affected the impact glasses than affected the metallic spherules. The impact glasses primarily lost Au, while the metallic spherules lost Fe relative to other siderophile elements.

Mittlefehldt, David W.; See, T. H.; Scott, E. R. D.

1993-01-01

145

Thermophysical Properties of Liquid and Supercooled Rare Earth Elements Measured by an Electrostatic Levitator  

Microsoft Academic Search

Thermophysical properties of several rare earth elements have been measured using electrostatic levitation techniques. The understanding of the nature and behavior of rare earth metals in their liquid phases requires accurate val- ues of their physical properties. However, keeping the samples in their liquid phases free from contamination long enough to carry out measurements represents a formidable challenge. This is

Takehiko ISHIKAWA; Junpei T. OKADA; Jianqiang LI; Paul-François PARADIS; Yuki WATANABE

146

Refinement of Near Earth Asteroids' orbital elements via simultaneous measurements by two observers  

NASA Astrophysics Data System (ADS)

The aspects of triangulation of Near Earth Asteroids by two arbitrarily positioned observers (one spaceborne and the other Earth-bound, as well as both spaceborne) are being investigated, and the resulting orbital elements are compared to those gained through common orbital determination and refinement techniques. The main advantages of the method proposed in this work are, that given the approximate position of an asteroid, high quality orbital elements can be acquired very rapidly using two observations only.

Eggl, Siegfried

2011-03-01

147

Fractions!  

NSDL National Science Digital Library

On this page you will practice adding, subtracting, multiplying, and dividing fractions. 1. Practice identifying equivalent fractions. Finding equivalent fractions 2. Add and subtract fractions. The first levels have like denominators, but then the levels get harder with unlike denominators. Make sure you use some scratch paper. Get to the highest level you can! Fraction Race (adding and subtracting, like and unlike denominators) 3. Practice adding fractions with mixed numbers. Math splat -adding fractions using mixed numbers 4. Finally, get with a partner ...

Hbinggeli

2010-08-24

148

Rare earth element behavior in the development of energy resources  

SciTech Connect

The REE patterns in soil-soil extract-plant-coal-flyash are all identical, show a negative Eu anomaly, and follow a smooth function of the REE ionic radii. The patterns are similar to that observed in the secondary mineral apatite. Their enrichment factors in various liquefaction products and ash depositories of a coal fired power plant are nearly unity (Class 1). The REE do not chemically fractionate even in size fractions 25 ..mu..m-0.5 ..mu..m of flyash. Almost all (99%) of the REE are bound in an inorganic form in high temperature clay minerals. The remarkable similarity in REE patterns in a wide variety of matrices with REE content varying over six orders of magnitude demonstrates that the REE do not significantly fractionate during transformation from the geological-biological-geological chain over geological time scales.

Laul, J.C.

1984-04-02

149

Rare earth element complexation by carbonate and oxalate ions  

NASA Astrophysics Data System (ADS)

Rare earth carbonate and oxalate complexation constants have been determined through ex-amination of distribution equilibria between tributyl phosphate and an aqueous perchlorate phase. Carbonate complexation constants appropriate to the REE in seawater (25°C, 35%., 1 atm) can be described in terms of atomic number, Z. nlog sw?1 = 4.853 + 0.1135( Z - 57) - 0.003643( Z - 57) 2log sw?2 = 80.197 + 0.1730( Z - 57) - 0.002714( Z -57) 2 where sw? 1 = [MCO +3] /[M 3+][CO 2-3] T, sw? 2 = [M(CO 3) -3] /[M 3+][CO 2-3] 2' T [ M3+] is an uncomplexed rare earth concentration in seawater, [ MCO+3] and [ M( CO-3) 2] are carbonate complex concentrations, and [CO 2-3] T is the total (free plus ion paired) carbonate ion concentration in seawater (molal scale). Our analyses indicate that in seawater with a total carbonate ion concentration of 1.39 × 10 -4 moles/Kg H 2O, carbonate complexes for the lightest rare earth, La, constitute 86% of the total metal, 7% is free La 3+ and the remaining 7% exists as hydroxide, sulfate, chloride and fluoride complexes. For Lu, the heaviest rare earth, carbonate complexes are 98% of the total metal, 0.3% is uncomplexed and 1.5% is complexed with hydroxide, sulfate, chloride and fluoride. Oxalate and carbonate constants are linearly correlated. This correlation appears to be quite useful for estimating trivalent metal-arbonate stability constants from their respective oxalate stability constants.

Cantrell, Kirk J.; Byrne, Robert H.

1987-03-01

150

Volatile element abundance patterns and an early liquid water ocean on Earth  

Microsoft Academic Search

The abundances of the elements H, C, N, Ne, primordial Ar, Cl, Br, Kr, I and Xe, in the atmo-hydrosphere, continental crust and MORB-source mantle (termed the outer Earth reservoirs (OER)) are examined and compared with solar matter and an average of carbonaceous chondrites (CC). The aim is to assess the likelihood of various possible sources for these volatile elements

Jan D Kramers

2003-01-01

151

Separation method and yields of small quantities of rare earth elements  

Microsoft Academic Search

The EMIS PARSIFAL was designed to purify very small quantities of radioactive isotopes. Yields are therefore an important component of the separations. The ionization is done in a thermoionization source or a plasma source, according to the physical properties of the concerned elements. For rare earth elements (REE), hydroxides are electrodeposited on a tantalum wire; for thermoionization, the wire is

Y. Boulin; A. Juery

1992-01-01

152

Allanite: thorium and light rare earth element carrier in subducted crust  

Microsoft Academic Search

The investigation of deeply subducted eclogites from the Dora-Maira massif, Western Alps reveals that accessory minerals are important hosts for trace elements. Rutile contains most of the bulk rock Ti, Nb and Ta while zircon hosts nearly all Zr and Hf. More than 90% of the bulk rock light rare earth elements (LREE) and Th and about 75% of U

Jörg Hermann

2002-01-01

153

Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth  

NASA Astrophysics Data System (ADS)

The zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic fractionation induced by magmatic differentiation. In this study we present high-precision Zn isotope analyses of two sets of chemically diverse, cogenetic samples from Kilauea Iki lava lake, Hawaii, and Hekla volcano, Iceland, which both show clear evidence of having undergone variable and significant degrees of magmatic differentiation. The Kilauea Iki samples display small but resolvable variations in Zn isotope composition (0.26‰fractionation is likely a result of the crystallization of olivine and/or Fe-Ti oxides, which can both host Zn in their crystal structures. Samples from Hekla have a similar range of isotopic variation (0.22‰fractionation caused by magmatic differentiation is less significant (only 0.07‰) and no correlation between isotope composition and degree of differentiation is seen. We conclude that high temperature magmatic differentiation can cause Zn isotope fractionation that is resolvable at current levels of precision, but only in compositionally-evolved lithologies. With regards to primitive (ultramafic and basaltic) material, this signifies that the terrestrial mantle is essentially homogeneous with respect to Zn isotopes. Utilizing basaltic and ultramafic sample analyses, from different geologic settings, we estimate that the average Zn isotopic composition of Bulk Silicate Earth is ?66Zn=0.28±0.05‰ (2s.d.).

Chen, Heng; Savage, Paul S.; Teng, Fang-Zhen; Helz, Rosalind T.; Moynier, Frédéric

2013-05-01

154

A New Mixed Element Method for a Class of Time-Fractional Partial Differential Equations  

PubMed Central

A kind of new mixed element method for time-fractional partial differential equations is studied. The Caputo-fractional derivative of time direction is approximated by two-step difference method and the spatial direction is discretized by a new mixed element method, whose gradient belongs to the simple (L2(?)2) space replacing the complex H(div; ?) space. Some a priori error estimates in L2-norm for the scalar unknown u and in (L2)2-norm for its gradient ?. Moreover, we also discuss a priori error estimates in H1-norm for the scalar unknown u.

Li, Hong; Gao, Wei; He, Siriguleng; Fang, Zhichao

2014-01-01

155

Experimental productivity rate optimization of rare earth element separation through preparative solid phase extraction chromatography.  

PubMed

Separating individual rare earth elements from a complex mixture with several elements is difficult and this is emphasized for the middle elements: Samarium, Europium and Gadolinium. In this study we have accomplished an overloaded one-step separation of these rare earth elements through preparative ion-exchange high-performance liquid chromatography with an bis (2-ethylhexyl) phosphoric acid impregnated column and nitric acid as eluent. An inductively coupled plasma mass spectrometry unit was used for post column element detection. The main focus was to optimize the productivity rate, subject to a yield requirement of 80% and a purity requirement of 99% for each element, by varying the flow rate and batch load size. The optimal productivity rate in this study was 1.32kgSamarium/(hmcolumn(3)), 0.38kgEuropium/(hmcolumn(3)) and 0.81kgGadolinium/(hmcolumn(3)). PMID:24835593

Knutson, Hans-Kristian; Max-Hansen, Mark; Jönsson, Christian; Borg, Niklas; Nilsson, Bernt

2014-06-27

156

A predictive model for rare earth element partitioning between clinopyroxene and anhydrous silicate melt  

Microsoft Academic Search

We present a quantitative model to describe the partitioning of rare earth elements (REE) and Y between clinopyroxene and\\u000a anhydrous silicate melt as a function of pressure (P), temperature (T) and bulk composition (X). The model is based on the Brice (1975) equation, which relates the partition coefficient of element i (D\\u000a \\u000a i\\u000a ) to that of element o (D

Bernard J. Wood; Jonathan D. Blundy

1997-01-01

157

Competition between humic acid and carbonates for rare earth elements complexation.  

PubMed

The competitive binding of rare earth elements (REE) to humic acid (HA) and carbonates was studied experimentally at various pH and alkalinity values by combining ultrafiltration and inductively coupled plasma mass spectrometry techniques. The results show that the REE species occur as binary humate or carbonate complexes but not as ternary REE-carbonate-humate as previously proposed. The results also reveal the strong pH and alkalinity dependence of the competition as well as the existence of a systematic fractionation across the REE series. Specifically, carbonate complexation is at a maximum at pH 10 and increase with increasing alkalinity and with the atomic number of the REE (LuCO(3)>LaCO(3)). Modeling of the data using Model VI and recently published stability constants for complexation of REE by humic acid well reproduced the experimental data, confirming the ability of Model VI to accurately determine REE speciation in natural waters. This modeling also confirms the reliability of recently published stability constants. This work shed more light not only on the competition between carbonates and HA for REE complexation but also on the reliability of WHAM 6 and Model VI for calculating the speciation of REE with organic matter in alkaline organic-rich water. PMID:17052726

Pourret, Olivier; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

2007-01-01

158

Modeling of rare-earth element partitioning between particles and solution in aquatic environments  

SciTech Connect

The authors have modeled the partitioning of rare earth elements (REEs) between O-donor surface groups and aqueous solutions with a simple thermodynamic treatment. Their model predicts that the La-normalized ratios of adsorbed to dissolved REEs depend primarily on the first hydroxide binding contants of the REEs, their first and second carbonate complexing constants, and the ionic strength and carbonate concentration of the solution. For modern and for ancient seawater, they predict an overall light REE (LREE) enrichment of surfaces relative to coexisting aqueous solutions and a positive Eu anomaly in the adsorbed component. The REE pattern of average modern ocean water can be explained quantitatively if the oceans are equilibrated with particle surfaces having REE patterns similar to average upper continental crust. Applying their treatment to the REE patterns of sediments from the Archean Hamersley-basin iron formation, they show that the observed positive Eu anomalies and LREE depletions of these rocks can be qualitatively accounted for if a significant fraction of the REEs in these rocks were initially present as an adsorbed component equilibrated with Archean ocean water that had no Eu anomaly. This suggests that the sources of REEs in the Archean ocean could have been dominantly continental as they are today and that the observed positive Eu anomalies of banded iron formations need not be inherited from the aqueous solutions from which they were deposited and do not necessarily indicate a significant ocean hydrothermal component in these solutions. 42 refs., 3 figs.

Erel, Y.; Stolper, E.M. (California Inst. of Technology, Pasadena (United States))

1993-02-01

159

Rare earth element sorption onto hydrous manganese oxide: a modeling study.  

PubMed

Manganese oxides are important scavengers of rare earth elements (REE) in hydrosystems. However, it has been difficult to include Mn oxides in speciation models due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), as well as discrepancies between published sorption data and predictions using the available models. Surface complexation reactions for hydrous Mn oxide were described using a two surface site model and the diffuse double layer SCM. The specific surface area, surface side density, and pH(zpc) were fixed to 746 m2/g, 2.1 mmol/g, and 2.2, respectively. Two site types (?XOH and ?YOH) were also used with pK(a2) values of 2.35 (?XOH) and 6.06 (?YOH). The fraction of the high affinity sites was fixed at 0.36. Published REE sorption data were subsequently used to determine the equilibrium surface complexation constants, while considering the influence of pH, ionic strength, and metal loading. LogK increases from light REE to heavy REE and, more specifically, displays a convex tetrad effect. At low metal loading, the ?YOH site type strongly expresses its affinity toward REE, whereas at higher metal loading, the same is true for the ?XOH site type. This study thus provides evidence for heterogeneity in the distribution of the Mn oxide binding sites among REE. PMID:23266025

Pourret, Olivier; Davranche, Mélanie

2013-04-01

160

Neutron Induced Radioactivity in Certain Rare-Earth Elements  

Microsoft Academic Search

By activating specimens of lanthanum, neodymium, samarium, europium, gadolinium, and terbium in the Oak Ridge pile for a particularly long exposure, several hitherto unobserved radioactivities are found. Determinations are made of the half-lives and of the beta- and gamma-energies by absorption and spectrometric methods. Lanthanum and neodymium were the only elements showing no internal conversion lines. Terbium appears as a

J. M. Cork; R. G. Shreffler; C. M. Fowler

1948-01-01

161

Rare earth element zonation in Pacific ferromanganese nodules  

NASA Astrophysics Data System (ADS)

The lower surfaces of ferromanganese nodules from the north equatorial Pacific Ocean, which are enriched in Mn, Cu and Ni, and the upper surfaces, which are enriched in Fe, P and Co, have been analyzed for La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb. The REE contents are lower and the Ce anomaly is smaller in the lower surfaces than in the upper surfaces. The magnitude of the Ce anomaly increases with decreasing Mn/Fe ratio, indicative of a seawater origin. The zonal distribution of the other REE supports the conclusion derived previously from inter-nodule and nodule/sediment relationships that diagenetic fixation of rare earths in sediments affects their enrichment by nodular iron oxyhydroxides.

Elderfield, H.; Hawkesworth, C. J.; Greaves, M. J.; Calvert, S. E.

1981-07-01

162

Element-free Galerkin (EFG) method for analysis of the time-fractional partial differential equations  

NASA Astrophysics Data System (ADS)

The present paper deals with the numerical solution of time-fractional partial differential equations using the element-free Galerkin (EFG) method, which is based on the moving least-square approximation. Compared with numerical methods based on meshes, the EFG method for time-fractional partial differential equations needs only scattered nodes instead of meshing the domain of the problem. It neither requires element connectivity nor suffers much degradation in accuracy when nodal arrangements are very irregular. In this method, the first-order time derivative is replaced by the Caputo fractional derivative of order ? (0 < ? < 1). The Galerkin weak form is used to obtain the discrete equations, and the essential boundary conditions are enforced by the penalty method. Several numerical examples are presented and the results we obtained are in good agreement with the exact solutions.

Ge, Hong-Xia; Liu, Yong-Qing; Cheng, Rong-Jun

2012-01-01

163

Effect of rare earth elements on the microstructure of Mg-Al alloys  

Microsoft Academic Search

Purpose: The automotive use of magnesium is currently restricted to low-temperature structural components. Rare earth additions such as Ce, Nd, La and Pr are known to improve the creep performance. The aim of the research was to determine the effect of rare earths elements on the as-cast microstructure of magnesium alloys containing 4 wt% aluminum. Design\\/methodology\\/approach: The study was conducted

T. Rzycho?; A. Kie?bus

164

U.S. trade dispute with China over rare earth elements  

NASA Astrophysics Data System (ADS)

The U.S. government has brought a new trade case against China over rare earth elements (REE) as well as tungsten and molybdenum, President Barack Obama announced on 13 March. Japan and the European Union also have taken similar actions against China about REEs, which are a group of 17 chemically similar metallic elements that are used in a variety of electronic, optical, magnetic, and catalytic applications. REEs are plentiful in the Earth's crust, although China currently has about 37% of the world's reserves and accounts for more than 95% of the world's production of the elements, according to the British Geological Survey. The United States has requested consultations with China at the World Trade Organization (WTO) concerning “China's unfair export restraints on rare earths, as well as tungsten and molybdenum,” the Office of the United States Trade Representative announced in a 13 March statement.

Showstack, Randy

2012-03-01

165

Rare earths and other trace elements in Apollo 14 samples.  

NASA Technical Reports Server (NTRS)

REE and other trace elements have been determined in igneous rocks 14053, 14072, and 14310, in breccias 14063 and 14313, and in fines 14163. All materials analyzed have typical depletions of Eu except for feldspar fragments from the breccias and igneous fragments from 14063. Igneous rocks 14072 and 14053 have REE concentrations very similar to Apollo 12 basalts; 14310 has the highest REE concentrations yet observed for a large fragment of lunar basalt. The effects of crystallization of a basaltic liquid as a closed system on the concentrations of Sm and Eu in feldspar are considered. Small anorthositic fragments may have originated by simple crystallization from very highly differentiated basalt (KREEP) or by closed-system crystallization in a less differentiated starting material. Application of independent models of igneous differentiation to Sm and Eu in massive anorthosite 15415 and to Sm and Eu in lunar basalts suggests a common starting material with a ratio of concentrations of Sm and Eu about the same as that in chondrites and with concentrations of those elements about 15 times enriched over chondrites.

Helmke, P. A.; Haskin, L. A.; Korotev, R. L.; Ziege, K. E.

1972-01-01

166

INAA application in the assessment of chemical element mass fractions in adult and geriatric prostate glands.  

PubMed

The variation with age of the mass fraction of 37 chemical elements in intact nonhyperplastic prostate of 65 healthy 21-87 year old males was investigated by instrumental neutron activation analysis with high resolution spectrometry of short- and long-lived radionuclides. Mean values (M±S??) for mass fractions (mgkg(-1), dry mass basis) of the chemical elements studied were: Ag-0.055±0.007, Br-33.2±3.3, Ca-2150±118, Cl-13014±703, Co-0.038±0.003, Cr-0.47±0.05, Fe-99.3±6.1, Hg-0.044±0.006, K-11896±356, Mg-1149±68, Mn-1.41±0.07, Na-10886±339, Rb-12.3±0.6, Sb-0.049±0.005, Sc-0.021±0.003, Se-0.65±0.03, and Zn-795±71. The mass fraction of other chemical elements measured in this study were lower than the corresponding detection limits (mgkg(-1), dry mass basis): As<0.1, Au<0.01, Ba<100, Cd<2, Ce<0.1, Cs<0.05, Eu<0.001, Gd<0.02, Hf<0.2, La<0.5, Lu<0.003, Nd<0.1, Sm<0.01, Sr<3, Ta<0.01, Tb<0.03, Th<0.05, U<0.07, Yb<0.03, and Zr<0.3. This work revealed that there is a significant trend for increase with age in mass fractions of Co (p<0.0085), Fe (p<0.037), Hg (p<0.035), Sc (p<0.015), and Zn (p<0.0014) and for a decrease in the mass fraction of Mn (p<0.018) in prostates, obtained from young adult up to about 60 years, with age. In the nonhyperplastic prostates of males in the sixth to ninth decades, the magnitude of mass fractions of all chemical element were maintained at near constant levels. Our finding of correlation between the prostatic chemical element mass fractions indicates that there is a great variation of chemical element relationships with age. PMID:24704913

Zaichick, Vladimir; Zaichick, Sofia

2014-08-01

167

Lack of chemical fractionation in major and minor elements during agglutinate formation. [in lunar soil  

NASA Technical Reports Server (NTRS)

Rhodes et al. (1975, 1976) and Adams et al. (1975) have reported that the agglutinate fraction of the soils on the lunar surface displays a marked enrichment in Fe, Mg, Ti, K, and La, and a depletion in Ca, Na, Al, and Eu, relative to the bulk soils. The reported investigation is concerned with a testing of the theory of chemical fractionation involving magnetic separation which was developed in connection with these findings. Soils 64421 and 71501 were sieved and the magnetic fractions separated according to the method developed by Adams and McCord (1973). Analyses of agglutinitic glass did not indicate any appreciable chemical fractionation for the major and minor elements accompanying the agglutination process. It was found that most, if not all fractionations reported can be accounted for completely by the magnetic nonagglutinate impurities in the agglutinate fraction. It is, therefore, concluded that there appears to be no reason to make use of any chemical fractionation theory, whose validity remains to be demonstrated.

Hu, H.-N.; Taylor, L. A.

1977-01-01

168

[Geochemical characteristics of rare earth elements on sunflower growing area in the west of Jilin Province].  

PubMed

Soil and plant samples were collected from the sunflower growing area in the west of Jilin province. A variety of ancillary methods were used to determine the soil element content. Then the rare earth elements geochemistry in soil was studied, and the correlation of REEs in this region with other elements and the quality of plant was investigated. The results show that, (1) REE content of the soil in Nong'an is relatively higher to those in Daan and Tongyu. Distribution pattern of rare earth elements in soil for the right tilt of the light rare earth enrichment patterns which is consistent with the national distribution pattern of rare earth elements; (2) REE contents in the three studying areas in the soil are different, and this primarily relates to the soil parent materials; (3) The REEs which positively correlate with soil available potassium are Se, Fe2O3, Ti, P, Mn, Cu, Zn, Cr, Mo, B, F. The protein content of sunflower seeds has a negative correlation with REE. With the exception of Lu, all REEs show a similar correlation. PMID:21922834

Li, Shu-Jie; Dou, Sen; Wang, Li-Min; Liu, Zhao-Shun

2011-07-01

169

Alkaline-earth metal and rare-earth element incorporation control by ionic radius and growth rate on a stalagmite from the Chauvet Cave, Southeastern France  

Microsoft Academic Search

A multi-element study involving major alkaline-earth cations (Mg, Ca, Sr, Ba) and trace elements like Na, U, Mn, Y and Rare Earth Elements (REE) in calcite of a stalagmite from the Chauvet Cave (SE of France) was carried out using ICP-QMS analysis. This study focused on the Chau-stm6 stalagmite which displays a record of the Last Deglaciation until the end

Clément Bourdin; Eric Douville; Dominique Genty

2011-01-01

170

[Study on speciation and fractionation of rare earth eleinents in surface sediments in Gansu, Ningxia and Inner Mongolia sections of Yellow River].  

PubMed

In the present paper, BCR sequential extraction and high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) were performed to analyze the speciation contents of 14 kinds of rare earth elements (REE) in the surface sediments from 12 sampling sites (S1-S12) in Gansu, Ningxia and Inner Mongolia Sections of Yellow River, and REE fractionation were also studied. The results indicated that the contents of REE in 12 sediment samples werethe same order. The average contents of 14 rare earth elements were in this order: Ce(66.4)>La(35.8)>Nd(28.6)>Pr(7.88)>Sm(5.87) >Gd(5.01)>Dy (4.53)>Yb(2.86)>Er(2.51)>Eu(1.31)>Ho(0.856)>Tb(0.760)>Tm(0.428)>Lu(0.404), which were similar to the Chinese soil background. The residual fractions of all elements were present at the highest percentages(71.9%-93.9%), which indicated that the bioavailability or environmental impact was low. The percentage of reducible fraction was the lowest, ranged from 0. 20% to 3. 87% with the mean value of 0.83%, while the oxidizable fraction percentage(7.61%) was close to acid-soluble fraction(7.69%). But in Maqu (S12), oxidizable percentage (16.1%) was significantly higher than the acid-soluble fraction (1.73%). Correlation analysis showed that there was a significant positive correlation between total organic carbon (TOC) content and oxidizable percentage, and the correlation coefficients were between 0.763 and 0.914. REE fractionation results showed that: the contents of REE in surface sediments of Gansu, Ningxia and Inner Mongolia Sections of Yellow River were mainly from soil weathering, with light-REE enrichment and Eu depletion. The chondrite-normalized curve implied that La and Ce in Jinshawan (S8) and Baotou-Dengkou (S1) and heavy REE at all the sampling points might have external REE sources. PMID:23705457

Liu, Jing-Jun; Lai, Zi-Juan; Liu, Ying

2013-03-01

171

Elemental fractionation of glass using laser ablation inductively coupled plasma mass spectrometry  

SciTech Connect

Three laser wavelengths (1064, 532, and 266 nm) were employed for laser ablation at varied laser pulse energies to study the effect of irradiance and wavelength upon analytical results for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Two important results were observed and are reported here: (1) the intensity of the MS signal came to a local minimum when the laser focal point was on the sample surface, and (2) elemental fractionation based upon laser wavelength and laser pulse energy was observed. For the waste glass simulant studied, ablation with 1064-nm (IR) and 532-nm (green) radiation produced elemental fractionation that relates to the melting point of the elemental oxide, whereas with 266-nm (UV) ablation the response was independent of the elemental oxide melting point. At high laser powers, ablation at 266 nm produced an elemental bias based upon the mass of the elements. These observations suggest the use of ultraviolet radiation at low pulse energies to obtain improved analytical results. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

Figg, D. [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States)] [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States); Kahr, M.S. [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States)] [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States); [Orbital Sciences Corporation, 2771 North Garey Ave., Pomona, California 91767 (United States)

1997-08-01

172

Finite element formulation of viscoelastic sandwich beams using fractional derivative operators  

NASA Astrophysics Data System (ADS)

This paper presents a finite element formulation for transient dynamic analysis of sandwich beams with embedded viscoelastic material using fractional derivative constitutive equations. The sandwich configuration is composed of a viscoelastic core (based on Timoshenko theory) sandwiched between elastic faces (based on Euler-Bernoulli assumptions). The viscoelastic model used to describe the behavior of the core is a four-parameter fractional derivative model. Concerning the parameter identification, a strategy to estimate the fractional order of the time derivative and the relaxation time is outlined. Curve-fitting aspects are focused, showing a good agreement with experimental data. In order to implement the viscoelastic model into the finite element formulation, the Grünwald definition of the fractional operator is employed. To solve the equation of motion, a direct time integration method based on the implicit Newmark scheme is used. One of the particularities of the proposed algorithm lies in the storage of displacement history only, reducing considerably the numerical efforts related to the non-locality of fractional operators. After validations, numerical applications are presented in order to analyze truncation effects (fading memory phenomena) and solution convergence aspects.

Galucio, A. C.; Deü, J.-F.; Ohayon, R.

173

Concentrations of Elements in Sediments and Selective Fractions of Sediments, and in Natural Waters in Contact with Sediments from Lake Roosevelt, Washington, September 2004  

USGS Publications Warehouse

Twenty-eight composite and replicate sediment samples from 8 Lake Roosevelt sites were collected and analyzed for 10 alkali and alkaline earth elements, 2 non-metals, 20 metals, and 4 lanthanide and actinide elements. All elements were detected in all sediment samples except for silver (95 percent of the elements detected for 1,008 analyses), which was detected only in 4 samples. Sequential selective extraction procedures were performed on single composite samples from the eight sites. The percentage of detections for the 31 elements analyzed ranged from 76 percent for the first extraction fraction using a weak extractant to 93 percent for the four-acid dissolution of the sediments remaining after the third sequential selective extraction. Water samples in various degrees of contact with the sediment were analyzed for 10 alkali and alkaline earth elements, 5 non-metals, 25 metals, and 16 lanthanide and actinide elements. The filtered water samples included 10 samples from the reservoir water column at 8 sites, 32 samples of porewater, 55 samples from reservoir water overlying sediments in 8 cores from the site incubated in a field laboratory, and 24 water samples that were filtered after being tumbled with sediments from 8 sites. Overall, the concentrations of only 37 percent of the 6,776 analyses of the 121 water samples were greater than the reporting limit. Selenium, bismuth, chromium, niobium, silver, and zirconium were not detected in any water samples. The percentage of concentrations for the water samples that were above the reporting limit ranged from 14 percent for the lanthanide and actinide elements to 77 percent for the alkali and alkaline earth elements. Concentrations were greater than reporting limits in only 23 percent of the analyses of reservoir water and 29 percent of the analyses of reservoir water overlying incubation cores. In contrast, 47 and 48 percent of the concentrations of porewater and water samples tumbled with sediments, respectively, were greater than the reporting limit.

Paulson, Anthony J.; Wagner, Richard J.; Sanzolone, Richard F.; Cox, Steven E.

2006-01-01

174

Determination of rare-earth elements in Luna 16 regolith sample by chemical spectral method  

NASA Technical Reports Server (NTRS)

An analysis was made of regolith from layer A of the Luna 16 sample for rare earth elements, by a chemical spectral method. Chemical and ion exchange concentrations were used to determine the content of 12 elements and Y at the level 0.001 to 0.0001 percent with 10 to 15 percent reproducibility of the emission determination. Results within the limits of reproducibility agree with data obtained by mass spectra, activation, and X-ray fluorescent methods.

Stroganova, N. S.; Ryabukhin, V. A.; Laktinova, N. V.; Ageyeva, L. V.; Galkina, I. P.; Gatinskaya, N. G.; Yermakov, A. N.; Karyakin, A. V.

1974-01-01

175

Partitioning of rare earth elements between clinopyroxene and silicate melt Crystal-chemical controls  

Microsoft Academic Search

This study explores some of the effects of major element compositional variations on the partitioning of trivalent rare earth elements between high-Ca clinopyroxene and silicate melt. Experiments performed in the system CaO?MgO?A12O3?SiO2 at 1 atm pressure, over a small temperature range, differentiate crystal-chemical controls on mineral\\/melt partitioning from the effects of pressure and temperature. The experimental results demonstrate that the

Glenn A. Gaetani; Timothy L. Grove

1995-01-01

176

Partitioning of rare earth elements between clinopyroxene and silicate melt Crystal-chemical controls  

Microsoft Academic Search

This study explores some of the effects of major element compositional variations on the partitioning of trivalent rare earth elements between high-Ca clinopyroxene and silicate melt. Experiments performed in the system CaO---MgO---A1 2 O 3 ---SiO 2 at 1 atm pressure, over a small temperature range, differentiate crystal-chemical controls on mineral\\/melt partitioning from the effects of pressure and temperature. The

Glenn A. Gaetani; Timothy L. Grove

1995-01-01

177

Experimental investigations of trace element fractionation in iron meteorites. III - Elemental partitioning in the system Fe-Ni-S-P  

NASA Technical Reports Server (NTRS)

Measurements of solid metal/liquid metal trace element partition coefficients, which are used to interpret the crystallization history of magmatic iron meteorite groups differ greatly between different research groups, using different experimental techniques. Specifically, partition coefficients measured utilizing 'static' experiments which approach equilibrium cannot be reconciled with the results of 'dynamic' experiments which mimic fractional crystallization. We report new tests of our 'static' experimental technique and demonstrate that our methodology yields reliable equilibrium values for Ni, P and Ge partition coefficients. Partition coefficients in the Fe-Ni-S-P system are well matched by interpolation between the Fe-Ni-S and Fe-Ni-P subsystems. In contrast, the predictions of 'dynamic' experiments do not agree with our measurements and, consequently, the ability of 'dynamic' experiments to reproduce iron meteorite Ge vs. Ni fractionation trends successfully must be regarded as fortuitous.

Malvin, D. J.; Jones, J. H.; Drake, M. J.

1986-01-01

178

Mutual influence of elements during coprecipitation. Cocrystallization of rare-earth elements under conditions for the formation of double sulfates of alkali and alkaline-earth metals  

SciTech Connect

This paper studies the coprecipitation of rare-earth metals under conditions for the crystallization of double salts in other sulfate systems, as well as the possibility of the employment of these double salts for the selective preconcentration of rare-earth metals from solutions of complex composition. The influence of electrolytes containing and not containing an element which may act as a charge compensator during isomorphous substitution was studied. Data are presented on the coprecipitation of cerium (III) and lutetium under the conditions for the crystallization of the double salt K/sub 2/SR(SO/sub 4/)/sub 2/ in the presence of LiC1 and LiNO/sub 3/, as well as HC1 and HNO/sub 3/.

Tsizin, G.I.; Kalinchenko, N.B.; Malofeeva, G.I.; Marov, I.N.; Tobelko, K.I.; Urusov, V.S.

1985-04-20

179

Effect of rare earth elements on growth and antioxidant metabo- lism in Lemna minor L  

Microsoft Academic Search

Lemna minor is frequently used in bioremediation processes to remove nutrients and contaminants from waste water. In this work the response of L. minor to treatments with lanthanum nitrate and with a mix of several light rare earth elements (REE) nitrates was investigated. Preliminary results indicate that L. minor shows an overall good tolerance to the presence of REE in

Maria Paola; Costantino Paciolla; Luigi d'Aquino; Massimo Morgan; Franca Tommasi

180

SEDIMENT REWORKING AND TRANSPORT IN EASTERN LAKE SUPERIOR: IN SITU RARE EARTH ELEMENT TRACER STUDIES  

EPA Science Inventory

A rare earth element (REE) tracer pellet was deployed at the floor of the Ile Parisienne basin of eastern Lake Superior to measure representative sediment reworking and transport processes in the benthic boundary layer of the prnfundal Great Lakes. Samarium oxide, a high neutron-...

181

Behavior of Rare Earth Elements in Geothermal Systems: A New Exploration/Exploitation Tool.  

National Technical Information Service (NTIS)

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells hav...

S. A. Wood

2001-01-01

182

Investigating source areas of eroded sediments transported in concentrated overland flow using rare earth element tracers  

Microsoft Academic Search

Rare earth element oxides (REOs) have excellent potential for use as tracers in erosion studies. Using laboratory and field experiments we aimed to develop and test a simple application method for spreading REOs and to use REOs to determine the source of sediment to concentrated overland flow paths. Tracks left by farm machinery (tramlines) in fields act as concentrated flow

C. J. Stevens; J. N. Quinton

183

Rare earth element distributions in anoxic waters of the Cariaco Trench  

Microsoft Academic Search

The concentrations of dissolved and suspended particulate rare earth elements in the Cariaco Trench are reported. In solution all REE, notably Ce, show a sharp increase just at or below the oxic \\/ anoxic interface at 300 meters depth. Particulate concentrations show a complementary decrease at the same depth. The overlying oxic waters exhibit a negative Ce anomaly; the anoxic

Hein J. W. de Baar; Christopher R. German; Henry Elderfield; Pauline van Gaans

1988-01-01

184

Method for the Analysis of Rare Earth Elements in Natural Waters by Isotope Dilution Mass Spectrometry.  

National Technical Information Service (NTIS)

A method is described to measure rare-earth elements (REE) in natural water samples. An iron hydroxide precipitation followed by ion exchange chromatography is used to concentrate and separate the REE from other matrix components. Additionally, the rare-e...

D. L. Schneider J. M. Palmieri

1994-01-01

185

Behavior of Rare Earth Element In Geothermal Systems; A New Exploration\\/Exploitation Tool  

Microsoft Academic Search

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells have been sampled from a number of locations, including: (1) the North Island of New Zealand (1

Scott A. Wood

2002-01-01

186

Rare Earth Element Fluxes in Diverse Soils and Their Absorption by Coconut Palm  

Microsoft Academic Search

The pattern of uptake of six rare earth elements (REEs) [lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), and gadolinium (Gd)] by coconut palm (Cocos nucifera L.) from three types of soils varying widely in their chemical characteristics and monazite content were studied through soil and plant tissue analysis employing ICP?MS method. Absorption of the REEs by the

P. A. Wahid; N. V. Kamalam; R. Krishna Prabhu; J. K. Sekhar; S. Vijayalakshmi; T. R. Mahalingam; C. E. Ajith Kumar

2003-01-01

187

Undecaprenyl Pyrophosphate Involvement in Susceptibility of Bacillus subtilis to Rare Earth Elements  

PubMed Central

The rare earth element scandium has weak antibacterial potency. We identified a mutation responsible for a scandium-resistant phenotype in Bacillus subtilis. This mutation was found within the uppS gene, which encodes undecaprenyl pyrophosphate synthase, and designated uppS86 (for the Thr-to-Ile amino acid substitution at residue 86 of undecaprenyl pyrophosphate synthase). The uppS86 mutation also gave rise to increased resistance to bacitracin, which prevents cell wall synthesis by inhibiting the dephosphorylation of undecaprenyl pyrophosphate, in addition to enhanced amylase production. Conversely, overexpression of the wild-type uppS gene resulted in increased susceptibilities to both scandium and bacitracin. Moreover, the mutant lacking undecaprenyl pyrophosphate phosphatase (BcrC) showed increased susceptibility to all rare earth elements tested. These results suggest that the accumulation of undecaprenyl pyrophosphate renders cells more susceptible to rare earth elements. The availability of undecaprenyl pyrophosphate may be an important determinant for susceptibility to rare earth elements, such as scandium.

Ochi, Kozo

2012-01-01

188

Composition of the earth's upper mantle. I - Siderophile trace elements in ultramafic nodules  

NASA Technical Reports Server (NTRS)

The considered investigation is concerned with a reexamination of the question of the distribution of siderophile elements in the earth's upper mantle, taking into account a more unified data base which is now available. A comprehensive suite of ultramafic inclusions was collected as part of the Basaltic Volcanism Study Project and has been analyzed by instrument neutron activation analysis for major, minor, and some lithophile trace elements. In addition, 18 of these rocks and the important sheared garnet lherzolite PHN 1611 have been analyzed by means of radiochemical neutron activation analysis for 7 siderophile elements (Au, Ge, Ir, Ni, Os, Pd, and Re) and 9 volatile elements (Ag, Bi, Cd, In, Sb, Se, Te, Tl, and Zn). The siderophile element data reveal interesting inter-element correlations, which were not apparent from the compiled abundance tables of Ringwood and Kesson (1976) and Chou (1978).

Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

1981-01-01

189

The Formation of Sulfate and Elemental Sulfur Aerosols Under Varying Laboratory Conditions: Implications for Early Earth  

NASA Technical Reports Server (NTRS)

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45 x 10(exp 9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO2) by UV light with lambda < 220 nm has been shown in models and some initial laboratory studies to create a S-MIF; however, sulfur must leave the atmosphere in at least two chemically different forms to preserve any S-MIF signature. Two commonly cited examples of chemically different sulfur species that could have exited the atmosphere are elemental sulfur (S8) and sulfuric acid (H2S04) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO2 either photolyzes at wavelengths from 115 to 400 nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H2) or methane (CH4), increased the formation of S8. With UV photolysis, formation of S8 aerosols is highly dependent on the initial SO2 pressure; and S8 is only formed at a 2% SO2 mixing ratio and greater in the absence of a reductant, and at a 0.2% SO2 mixing ratio and greater in the presence of 1000 ppmv CH4. We also found that organosulfur compounds are formed from the photolysis of CH4 and moderate amounts of SO2, The implications for sulfur aerosols on early Earth are discussed.

DeWitt, H. Langley; Hasenkopf, Christa A.; Trainer, Melissa G.; Farmer, Delphine K.; Jimenez, Jose L.; McKay, Christopher P.; Toon, Owen B.; Tolbert, Margaret A.

2010-01-01

190

Revisiting the elemental composition and the calorific value of the organic fraction of municipal solid wastes  

Microsoft Academic Search

In this work, the elemental content (C,N,H,S,O), the organic matter content and the calorific value of various organic components that are commonly found in the municipal solid waste stream were measured. The objective of this work was to develop an empirical equation to describe the calorific value of the organic fraction of municipal solid waste as a function of its

Dimitrios Komilis; Alexandros Evangelou; Georgios Giannakis; Constantinos Lymperis

191

2013 Southeast Asian smoke haze: fractionation of particulate-bound elements and associated health risk.  

PubMed

Recurring biomass burning-induced smoke haze is a serious regional air pollution problem in Southeast Asia (SEA). The June 2013 haze episode was one of the worst air pollution events in SEA. Size segregated particulate samples (2.5-1.0 ?m; 1.0-0.5 ?m; 0.5- 0.2 ?m; and <0.2 ?m) were collected during the June 2013 haze episode. PM2.5 concentrations were elevated (up to 329 ?g/m(3)) during the haze episode, compared to those during the nonhaze period (11-21 ?g/m(3)). Chemical fractionation of particulate-bound trace elements (B, Ca, K, Fe, Al, Ni, Zn, Mg, Se, Cu, Cr, As, Mn, Pb, Co, and Cd) was done using sequential extraction procedures. There was a 10-fold increase in the concentration of K, an inorganic tracer of biomass burning. A major fraction (>60%) of the elements was present in oxidizable and residual fractions while the bioavailable (exchangeable) fraction accounted for up to 20% for most of the elements except K and Mn. Deposition of inhaled potentially toxic trace elements in various regions of the human respiratory system was estimated using a Multiple-Path Particle Dosimetry model. The particle depositions in the respiratory system tend to be more severe during hazy days than those during nonhazy days. A prolonged exposure to finer particles can thus cause adverse health outcomes during hazy days. Health risk estimates revealed that the excessive lifetime carcinogenic risk to individuals exposed to biomass burning-impacted aerosols (18 ± 1 × 10(-6)) increased significantly (P < 0.05) compared to those who exposed to urban air (12 ± 2 × 10(-6)). PMID:24646334

Betha, Raghu; Behera, Sailesh N; Balasubramanian, Rajasekhar

2014-04-15

192

The behaviour of trace and rare earth elements (REE) during hydrothermal alteration in the Rangan area (Central Iran)  

NASA Astrophysics Data System (ADS)

The rhyolitic dome in the Rangan area has been subjected to hydrothermal alterations by two different systems, (1) A fossil magmatic-hydrothermal system with a powerful thermal engine of a deep monzodioritic magma, (2) An active hydrothermal system dominated by meteoric water. Based on mineralogical and geochemical studies, three different alteration facies have been identified (phyllic, advanced argillic and silicic) with notable differences in REE and other trace elements behaviour. In the phyllic alteration zone with assemblage minerals such as sericite, pyrite, quartz, kaolinite, LREE are relatively depleted whereas HREE are enriched. The advanced argillic zone is identified by the presence of alunite-jarosite and pyrophyllite as well as immobility of LREE and depletion in HREE. In the silicic zone, most of LREE are depleted but HREE patterns are unchanged compared to their fresh rock equivalents. All the REE fractionation ratios (La/Yb) cn, (La/Sm) cn, (Tb/Yb) cn, (Ce/Ce ?) cn and (Eu/Eu ?) cn are low in the phyllic altered facies. (Eu/Eu ?) cn in both advanced and silicic facies is low too. In all alteration zones, high field strength elements (HFSE) (e.g. Ti, Zr, Nb) are depleted whereas transition elements (e.g. V, Cr, Co, Ni, Fe) are enriched. Geochemically speaking, trace and rare earth elements behave highly selective in different facies.

Parsapoor, A.; Khalili, M.; Mackizadeh, M. A.

2009-02-01

193

Uranium and rare earth elements in CO 2-rich waters from Vals-les-Bains (France)  

NASA Astrophysics Data System (ADS)

Waters from springs at Vals-les-Bains result from the mixing of a CO 2-rich, highly mineralized water with dilute, shallow subsurface water. Total content of dissolved species vary from 5 mmol/1 to 100 mmol/1. For many elements, mixing of these waters is non-linear (non-conservative) and further water-rock reactions take place. The pH is controlled by CO 2 outgassing, redox conditions are controlled by both the iron hydroxide-siderite buffer and the introduction of oxygen with shallow subsurface waters. Among the major elements, concentrations of Ca, Mg, Mn, Fe, are related to mixing, CO 2 outgassing and carbonate precipitation. Uranium shows a complex behaviour controlled by carbonate complexing, redox conditions, mixing of waters and leaching from the rocks. The 234U /238U activity ratio is near secular equilibrium. In the more dilute waters, dissolved rare earth element (REE) patterns are almost flat with a slight negative Eu anomaly. In the concentrated waters, heavy rare earth elements (Gd-Yb, HREE) are strongly enriched relative to light rare earth elements (Ce-Eu, LREE). We relate the enrichment in HREE to water chemistry and to complexing with carbonate species.

Michard, Annie; Beaucaire, Catherine; Michard, Gil

1987-04-01

194

[Determination of ten trace rare earth elements in the sample by atomic emission spectrometry].  

PubMed

This paper describes the determination of trace La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Yb and Lu in the sample, using carbon powder, potassium sulfate, barium sulfate, strontium sulfate, and scandium chloride as buffer, by atomic emission spectrometry (AES). Scandium was selected as internal standard line. Sample separation and chemical treatment were not required. The sample was directly loaded into ordinary electrode. The method is simple, rapid and accurate. The determination requirement and influence factors were studied. A new method was developed for the determination of ten rare earth elements, for which the detection limit is smaller than 0.030%, and the range of the recovery is 94%-105%. The results of these elements in standard sample are in agreement with certified values, and the RSD is smaller than 5% (n = 9). The method has been applied to the determination of ten rare earth elements with satisfactory results. PMID:16379301

Li, Hui-zhi; Zhai, Dian-tang; Zhang, Jin; Pei, Mei-shan

2005-09-01

195

Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions  

NASA Astrophysics Data System (ADS)

The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K2O and an increase in FeO + MgO in the restites. The most characteristic trace element feature of the Kokchetav UHP restites is a strong depletion in light rare earth elements (LREE), Th and U. This is attributed to complete dissolution of monazite/allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to ~1,000 °C. Large ion lithophile elements (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace element fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.

Stepanov, Aleksandr S.; Hermann, Joerg; Korsakov, Andrey V.; Rubatto, Daniela

2014-05-01

196

Study of rare earth element effect on microstructures and mechanical properties of an Al-Cu-Mg-Si cast alloy  

Microsoft Academic Search

The improvements of microstructures and properties of a high strength aluminum cast alloy were studied. The effects of rare earth elements on the microstructures and mechanical properties of the high strength cast alloy Al-Cu-Mg-Si were investigated. The result shows that the addition of rare earth elements can change the microstructures in refining the grain size of the alloy and making

Weiwei WAN; Jianmin HAN; Weijing LI; Jinhua WANG

2006-01-01

197

Origin of the earth's moon - Constraints from alkali volatile trace elements  

NASA Astrophysics Data System (ADS)

Although the moon is depleted in volatile elements compared to the earth, these depletions are not in accord with simple volatility. For example, the Cs/Rb ratios of the earth and moon inferred from basalt are approximately one seventh and one half of the CI ratio, respectively. Volatility considerations alone predict that the lunar Cs/Rb ratio should be equal to or lower than the terrestrial ratio if the moon was derived entirely from earth mantle material. Thus hypotheses such as rotational fission which invoke derivation of lunar material entirely from the earth's mantle may be excluded. The collisional ejection hypothesis of lunar origin requires at least 18 percent of lunar material to be derived from a projectile with dehydrated CI composition to match the lunar Cs/Rb ratio, and 25-50 percent to match both the lunar Cs/Rb ratio and absolute concentrations of Cs and Rb. It remains to be demonstrated that this relatively large contribution of projectile material is consistent with other elemental abundances and element ratios in the moon.

Kreutzberger, M. E.; Drake, M. J.; Jones, J. H.

1986-01-01

198

Rare Earth Element Measurements of Melilite and Fassaite in Allende Cai by Nanosims  

NASA Technical Reports Server (NTRS)

The rare earth elements (REEs) are concentrated in CAIs by approx. 20 times the chondritic average [e.g., 1]. The REEs in CAIs are important to understand processes of CAI formation including the role of volatilization, condensation, and fractional crystallization [1,2]. REE measurements are a well established application of ion microprobes [e.g., 3]. However the spatial resolution of REE measurements by ion microprobe (approx.20 m) is not adequate to resolve heterogeneous distributions of REEs among/within minerals. We have developed methods for measuring REE with the NanoSIMS 50L at smaller spatial scales. Here we present our initial measurements of REEs in melilite and fassaite in an Allende Type-A CAI with the JSC NanoSIMS 50L. We found that the key parameters for accurate REE abundance measurements differ between the NanoSIMS and conventional SIMS, in particular the oxide-to-element ratios, the relative sensitivity factors, the energy distributions, and requisite energy offset. Our REE abundance measurements of the 100 ppm REE diopside glass standards yielded good reproducibility and accuracy, 0.5-2.5 % and 5-25 %, respectively. We determined abundances and spatial distributions of REEs in core and rim within single crystals of fassaite, and adjacent melilite with 5-10 m spatial resolution. The REE abundances in fassaite core and rim are 20-100 times CI abundance but show a large negative Eu anomaly, exhibiting a well-defined Group III pattern. This is consistent with previous work [4]. On the other hand, adjacent melilite shows modified Group II pattern with no strong depletions of Eu and Yb, and no Tm positive anomaly. REE abundances (2-10 x CI) were lower than that of fassaite. These patterns suggest that fassaite crystallized first followed by a crystallization of melilite from the residual melt. In future work, we will carry out a correlated study of O and Mg isotopes and REEs of the CAI in order to better understand the nature and timescales of its formation process and subsequent metamorphic history.

Ito, M.; Messenger, Scott

2009-01-01

199

Heavy metals and rare earth elements source-sink in some Egyptian cigarettes as determined by neutron activation analysis.  

PubMed

Heavy metals and rare earth elements in two types of cigarettes were studied. The contents of trace elements were determined by using delayed neutron activation analysis. In the present study 11 elements have been detected in popular and fine brand cigarettes marketed in Egypt. Evaluation of these elements with their potential hazards for smokers is briefly discussed. The material balance (source and sink) for each element was determined. Also the ratio of element recovery to the total amount was assessed. PMID:10376325

Nada, A; Abdel-Wahab, M; Sroor, A; Abdel-Haleem, A S; Abdel-Sabour, M F

1999-07-01

200

Elemental and spectroscopic characterization of fractions of an acidic extract of oil sands process water.  

PubMed

'Naphthenic acids' (NAs) in petroleum produced water and oil sands process water (OSPW), have been implicated in toxicological effects. However, many are not well characterized. A method for fractionation of NAs of an OSPW was used herein and a multi-method characterization of the fractions conducted. The unfractionated OSPW acidic extract was characterized by elemental analysis, electrospray ionization-Orbitrap-mass spectrometry (ESI-MS), and an esterified extract by Fourier Transform infrared (FTIR) and ultraviolet-visible (UV) absorption spectroscopy and by comprehensive multidimensional gas chromatography-MS (GCxGC-MS). Methyl esters were fractionated by argentation solid phase extraction (Ag(+) SPE) and fractions eluting with: hexane; diethyl ether: hexane and diethyl ether, examined. Each was weighed, examined by elemental analysis, FTIR, UV, GC-MS and GCxGC-MS (both nominal and high resolution MS). The ether fraction, containing sulfur, was also examined by GCxGC-sulfur chemiluminescence detection (GCxGC-SCD). The major ions detected by ESI-MS in the OSPW extract were assigned to alicyclic and aromatic 'O2' acids; sulfur was also present. Components recovered by Ag(+) SPE were also methyl esters of alicyclic and aromatic acids; these contained little sulfur or nitrogen. FTIR spectra showed that hydroxy acids and sulfoxides were absent or minor. UV spectra, along with the C/H ratio, further confirmed the aromaticity of the hexane:ether eluate. The more minor ether eluate contained further aromatics and 1.5% sulfur. FTIR spectra indicated free carboxylic acids, in addition to esters. Four major sulfur compounds were detected by GCxGC-SCD. GCxGC-high resolution MS indicated these were methyl esters of C18 S-containing, diaromatics with ?C3 carboxylic acid side chains. PMID:23856466

Jones, D; Scarlett, A G; West, C E; Frank, R A; Gieleciak, R; Hager, D; Pureveen, J; Tegelaar, E; Rowland, S J

2013-11-01

201

Rare earth elements as nonabsorbable fecal markers in studies of iron absorption.  

PubMed

The use of rare earth elements as nonabsorbable fecal markers for studies of iron absorption from sources labeled extrinsically with stable isotopes was evaluated. On 3 successive days 13 healthy fasting adults were given different stable isotopes of iron with samarium, ytterbium, or dysprosium. On day 1, three meals were given with 57Fe (1 mg per meal) plus samarium (0.33 mg per meal); on day 2, identical meals (taken with a calcium supplement to reduce iron bioavailability) were given with equivalent amounts of 58Fe-labeled iron and ytterbium; on day 3, a well-absorbed reference dose of 54Fe (3 mg) was given with 1 mg Dy. A complete fecal collection was carried out for 5-9 d and each stool was analyzed for rare earth elements by inductively coupled plasma-mass spectrometry and iron isotopes by thermal ionization quadrupole mass spectrometry. Mean recovery of rare earth elements was 101%, indicating that they are totally unabsorbed. The excretory pattern of the iron isotopes and the rare earth elements was very similar; the correlation coefficients between samarium and 57Fe, ytterbium and 58Fe, and dysprosium and 54Fe were 0.992, 0.989, and 0.988, respectively (P < 0.001). Iron absorption was calculated as the difference between isotope dose and fecal excretion. Mean (+/-SEM) iron absorption was 16.7 +/- 2.4%, 4.3 +/- 1.6%, and 40.3 +/- 3.1% on days 1-3, respectively. Predicted values estimated from the first 4 d of pooled feces, using the rare earth element recovery data to produce corrected figures for unabsorbed isotope, were in close agreement: 19.1 +/- 2.1%, 4.6 +/- 1.7%, and 40.8 +/- 3.1%, respectively (P < 0.001). With the diet of medium iron bioavailability and with the highly bioavailable reference dose it was possible to predict iron absorption accurately from only one or two stools, provided that they were sufficiently enriched with isotope and a rare earth element. PMID:9094881

Fairweather-Tait, S J; Minihane, A M; Eagles, J; Owen, L; Crews, H M

1997-04-01

202

Trace Element and Pb Isotope Constraints on Dynamic Evolution of Earth Reservoirs  

NASA Astrophysics Data System (ADS)

Advances in interpretation of Pb isotope systematics provide constraints for modelling Earth evolution. Such improved understanding of Pb isotope systematics has coincided with advances in techniques for accurate Pb isotope ratio measurement by MC-ICPMS. Continental growth since 3.75 Ga has occurred at convergent margins via dehydration of subducted slabs and supra-subduction zone melting. Nb is preferentially retained in slabs relative to U and Th, which are lost to escaping fluids. Over time, the depleted upper mantle (DM) lost U and Th relative to Nb. Thus Nb/Th and Nb/U of UM mirror amount of continental crust present. Because Nb, Th and U are similarly incompatible during MORB melting, temporal Nb-Th-U systematics of mantle can be reconstructed from uncontaminated, depleted-mantle derived rocks1. Excellent agreement exists between crustal growth curve based on Nb/Th and those based on Pb isotope systematics2 and geophysics 3. Temporal variation of Nb/U reflects crustal extraction until 2 Ga. It then reflects preferential U recycling into DM, constraining timing of preservation of a pandemic oxygenated atmosphere. Increase in atmospheric O2 explains the second Pb paradox and refines understanding of DM evolution. Key to understanding mantle Pb isotope evolution is the realization that DM has highly dynamic U/Pb and Th/U ratios relative to undegassed lower mantle (LM). Thus, so-called OIB EM-1 reservoir could reflect LM4. Pb data for Phanerozoic and Proterozoic Gp 2 kimberlites from South Africa plot in thorogenic and uranogenic Pb space consistent with a LM source [4]. Mineralogically, chemically and isotopically different Gp 1 kimberlites, which are readily discernable in plots of PM normalized Ta/U and Nb/Th have very radiogenic 206Pb/204Pb and 208Pb/204Pb but relatively unradiogenic 207Pb/204Pb, compositions identical to HIMU OIB's. We have suggested in [4] that the HIMU isotopic composition can be derived from EM-1 during a transient <100 Ma stage of strong U/Pb fractionation. Recent discovery of LM baddeleyite provides the mineralogical rationale for this scenario. Subducted oceanic crust and continental sediment are unlikely candidates for OIB HIMU source, as trace element fractionation during subduction induced dehydration lowers U/Pb ratio of residual slabs. This has important consequences for genesis of lamproites and minettes. In an speculative model by [5], and supported by seismic tomography, TZ was interpreted as a graveyard for slabs containing high pressure mineralogies such as majorite, NAL phases and hollandite. Partial melts derived from such an environment yield alkaline rocks with Pb isotopic compositions plotting to the left of the Geochron. Significantly, this interpretation is now supported by Pb isotopic data for TZ macrocryst suite xenoliths. An unrelated, now extinct HIMU reservoir, is inferred from Pb isotopes in TTG gneisses in some Archean cratons. Evolution of this source is reflected in Pb isotopic data for galena from Isua that require source separation before 4.3 Ga. The only conceivable long-lived source would have been Hadean crust. Rare examples of pre-plate tectonics TTG gneisses with this isotopic memory occur in the NAC where feldspar Pb isotopes define rotated isochrons that intersect the transient HIMU evolution vector at the time of zircon crystallization of the gneiss protoliths. This transient early Archean HIMU reservoir was subsequently destroyed by subduction. 1Collerson&Kamber (1999) Science 283, 1519. 2Kramers&Tolstikhin (1997) Chem. Geol. 139, 75. 3Reymer&Schubert (1984) Tectonics 3, 63. 4Kamber&Collerson (1999) JGR 105, 25479. 5Ringwood (1994) Phys. Earth Planet. Int. 86, 5.

Collerson, K.; Kamber, B.

2001-12-01

203

Structural Responses and Finite Element Modeling of Hakka Tulou Rammed Earth Structures  

NASA Astrophysics Data System (ADS)

Hakka Tulous are rammed earth structures that have survived the effects of aging and natural elements upwards of even over a thousand years. These structures have housed the Hakka people of the Fujian Province, China in natural yet modern housing that has provided benefits over newer building materials. The key building material, rammed earth, which is used for the walls of the Hakka Tulou structures, has provided structural stability along with thermal comfort to the respective inhabitants of the Hakka Tulous. Through material testing and analysis this study has examined how the Tulou structures have maintained their structural stability while also providing thermal comfort. Reports of self healing cracks in the rammed earth walls were also analyzed for their validity in this study. The study has found that although the story of the self healing crack cannot be validated, there is reason to believe that with the existence of lime, some type of autogenous healing could occur on a small scale. The study has also found, through the use of nondestructive testing, that both the internal wooden systems (flooring, roof, and column support) and the rammed earth walls, are still structurally sound. Also, rammed earth's high thermal mass along with the use of sufficient shading has allowed for a delay release of heat energy from the walls of the Tulous, thus providing thermal comfort that can be felt during both night and day temperatures. The Hakka Tulou structures have been found to resist destruction from natural disasters such as strong earthquakes even when more modern construction has not. Through finite element modeling, this study has shown that the high volume of rammed earth used in the construction of the Hakka Tulous helps dissipate lateral force energy into much lower stresses for the rammed earth wall. This absorption of lateral force energy allows the rammed earth structures to survive even the strongest of earthquakes experienced in the region. The Hakka Tulou, if rated by the LEED green building certification program, would earn the highest certification as this rammed earth construction has offered efficient living for hundreds of years. As historic as these rammed earth structures are, they present an environmentally friendly option to structures of the future.

Sranislawski, Daniel

204

The group separation of the rare-earth elements and yttrium from geologic materials by cation-exchange chromatography  

USGS Publications Warehouse

Demand is increasing for the determination of the rare-earth elements (REE) and yttrium in geologic materials. Due to their low natural abundance in many materials and the interferences that occur in many methods of determination, a separation procedure utilizing gradient strong-acid cation-exchange chromatography is often used to preconcentrate and isolate these elements from the host-rock matrix. Two separate gradient strong-acid cation-exchange procedures were characterized and the major elements as well as those elements thought to provide the greatest interference for the determination of the REE in geologic materials were tested for separation from the REE. Simultaneous inductively coupled argon plasma-atomic emission spectroscopy (ICAP-AES) measurements were used to construct the chromatograms for the elution studies, allowing the elution patterns of all the elements of interest to be determined in a single fraction of eluent. As a rock matrix, U.S. Geological Survey standard reference BCR-1 basalt was digested using both an acid decomposition procedure and a lithium metaborate fusion. Hydrochloric and nitric acids were tested as eluents and chromatograms were plotted using the ICAP-AES data; and we observed substantial differences in the elution patterns of the REE and as well as in the solution patterns of Ba, Ca, Fe and Sr. The nitric acid elution required substantially less eluent to elute the REE and Y as a group when compared to the hydrochloric acid elution, and provided a clearer separation of the REE from interfering and matrix elements. ?? 1984.

Crock, J. G.; Lichte, F. E.; Wildeman, T. R.

1984-01-01

205

Thermal effects on rare earth element and strontium isotope chemistry in single conodont elements  

Microsoft Academic Search

A low-blank, high sensitivity isotope dilution, ICP-MS analytical technique has been used to obtain REE abundance data from single conodont elements weighing as little as 5 ?g. Sr isotopes can also be measured from the column eluants enabling Sr isotope ratios and REE abundance to be determined from the same dissolution. Results are comparable to published analyses comprising tens to

H. A. Armstrong; D. G. Pearson; M. Griselin

2001-01-01

206

Potential toxic element fractionation and phytoavailability assessment in technosoils from former smelting and mining areas  

NASA Astrophysics Data System (ADS)

High metal and metalloid concentrations in soils have negative effects on terrestrial ecosystems and generate potential health risk. Mining and smelting activities are the major source of metal contamination by release a huge amounts of these potentially toxic elements (PTE) into the environment. Since the determination of the total concentration of PTE in soils does not give sufficient information about their mobility and toxicity, additional information on their bioavailability and their chemical speciation is required. Our study aimed at reporting the chemical fractionation and phytoavailability assessment of several PTE (Zn, Pb, Cd, As and Sb) in contaminated technosoils of two former smelting and mining areas. Soil samples were taken from a metallophyte grassland contaminated with Zn, Pb and Cd located at Mortagne - du -Nord (MDN) (North France) and from a former mining settling basin contaminated with As, Pb and Sb located at la Petite Faye (LPF) (Limoges district, France). Two sequential extraction schemes were used to evaluate the PTE speciation in various technosoils as operationally defined fractions. The extraction schemes used in this study were the Tessier's scheme and a modified BCR scheme. The fractions were rearranged into four equivalent fractions defined as acid soluble, reducible, oxidisable and residual fraction. To assess the metals and metalloids phytoavailability a series of selective single extraction procedures (CaCl2, NaNO3, NH4NO3, DTPA and EDTA) were used together with short-term germination tests with dwarf beans whose primary leaves were analyzed for their PTE concentration after 21 days of sowing under controlled conditions (16h light/8h darkness regime, 25°C/21°C, relative humidity of 55 - 65% and photon flux of 150 ?E m-2s-1). Our results indicates that Zn, Cd and Pb were mainly associated with the acid soluble and reducible fractions for the MDN site, while As, Sb and Pb were mostly associated with residual fraction for the LPF site. The extraction capacity of the PTE followed the order: EDTA>DTPA>NH4NO3>CaCl2> NaNO3 for both studied locations. Pearson correlation coefficient analysis between the concentrations of PTE accumulated in the bean primary leaves with their extractable concentrations showed a positive significant correlation with dilute CaCl2 and unbuffered nitrate solutions extraction procedures. In contrast, for all studied elements, except for Pb, the complexing and chelating extractants (e.g. EDTA and DTPA) exhibited poor correlation with the dwarf bean leaves concentrations.

Qasim, Bashar; Motelica-Heino, Mikael

2014-05-01

207

Oxygen and sulfur isotope fractionation during anaerobic bacterial disproportionation of elemental sulfur  

NASA Astrophysics Data System (ADS)

Bacterial disproportionation of elemental sulfur is an important process in the sulfur cycle of natural sediments and leads to the formation of hydrogen sulfide and sulfate. The oxygen atoms in sulfate during this anaerobic process are completely derived from water according to the overall reaction: 4H 2O + 4S 0 ? 3H 2S + SO 42- + 2H +In the present study, stable oxygen isotope fractionation during formation of sulfate via this reaction was experimentally investigated for a pure culture (Desulfocapsa thiozymogenes) and an enrichment culture ("Kuhgraben") at 28°C. Synthetic FeCO 3 and FeOOH were used as scavengers for hydrogen sulfide to keep the disproportionation reaction exergonic and to suppress polysulfide formation and isotope exchange between elemental sulfur and hydrogen sulfide. Compared to water, dissolved sulfate was enriched in 18O by +17.4 ± 0.1‰ ( Desulfocapsa thiozymogenes) and +16.6 ± 0.5‰ (Kuhgraben) at cell specific sulfur disproportionation rates of 10 -15.4 ± 0.4 mol S° cell -1 h -1 and 10 -14.4 ± 0.9 mol S° cell -1 h -1, respectively. Oxygen isotope fractionation was not influenced by the type of iron-bearing scavenger used, corroborating earlier findings that H 2S oxidation by FeOOH yields elemental sulfur as the dominant oxidation product. Sulfite is suggested to be formed as a metabolic intermediate to facilitate isotope exchange with water. Due to bacterial disproportionation, dissolved sulfate was also enriched in 34S compared to elemental sulfur by +11.0 to +18.4‰ ( D. thiozymogenes) and +12.7 to +17.9‰ (Kuhgraben). FeS was depleted in 32S compared to elemental sulfur by -3.7 to -5.3‰ ( D. thiozymogenes).

Böttcher, M. E.; Thamdrup, B.; Vennemann, T. W.

2001-05-01

208

Synthesis of aluminum garnets of rare-earth elements and yttrium with combined deposition of hydroxides  

SciTech Connect

This work is concerned with the study of the mechanism of the formation of aluminum garnets of rare-earth elements as well as the conditions for their synthesis by the method of combined deposition of hydroxides. The deposition was conducted by continuously dripping a mixture of a 0.5 M solution of nitric acid salts of aluminum and rare-earth elements or yttrium into a 1 M solution of ammonium hydroxide while constantly mixing the suspension and monitoring the pH (9.5-10). The deposits were filtered, flushed with distilled water, and dried at 100-150/sup 0/C. The impurity content in the starting reagents did not exceed 10/sup -2/ mass %. The studies were carried out by means of thermal, complex thermal, and x-ray phase analysis.

Glushkova, V.B.; Zinov'ev, S.Yu.; Krzhizhanovskaya, V.A.; Kuznetsov, A.K.

1986-12-01

209

Composition of the earth's upper mantle. II - Volatile trace elements in ultramafic xenoliths  

NASA Technical Reports Server (NTRS)

Radiochemical neutron activation analysis was used to determine the nine volatile elements Ag, Bi, Cd, In, Sb, Se, Te, Tl, and Zn in 19 ultramafic rocks, consisting mainly of spinel and garnet lherzolites. A sheared garnet lherzolite, PHN 1611, may approximate undepleted mantle material and tends to have a higher volatile element content than the depleted mantle material represented by spinel lherzolites. Comparisons of continental basalts with PHN 1611 and of oceanic ridge basalts with spinel lherzolites show similar basalt: source material partition factors for eight of the nine volatile elements, Sb being the exception. The strong depletion of Te and Se in the mantle, relative to lithophile elements of similar volatility, suggests that 97% of the earth's S, Se and Te may be in the outer core.

Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

1980-01-01

210

The rare earth element geochemistry of Mono Lake water and the importance of carbonate complexing  

Microsoft Academic Search

Rare earth element (REE) concentrations for the alkaline, saline waters of Mono Lake in eastern California are reported. The total REE concentrations of the lake water ranged from 4,68 1 to 7,979 pmol kg- I. Shale-normalized REE profiles for the lake water indicate that the heavy REEs (HREE) are enriched 20-200 times over the light REEs (LREE) compared to shale.

KEVIN H. JOHANNESSON; W. BERRY LYONS

1994-01-01

211

Distribution of alkaline earth elements between aqueous solutions and polymeric sorbent impregnated with 8-hydroxyquinoline  

SciTech Connect

The interphase distribution of microimpurities of alkaline earth elements (AEE) between solutions of alkali metal chlorides and a macroporous styrene-divinyl-benzene copolymer impregnated with 8-hydroxyquinoline was studied. The influence of the phase composition on the distribution coefficients of AEE and 8-hydroxyquinoline was examined. The advantages of sorption of the impurities by an impregnated sorbent over liquid extraction for thorough purification of salt solutions were shown.

Turanov, A.N.; Kremenskaya, I.N.; Putrya, L.V.

1987-07-01

212

Encapsulation of the platinum and neighboring metals within cluster iodides of rare-earth elements  

Microsoft Academic Search

Syntheses of new cluster phases containing encapsulated heterometals have been explored through reactions between the rare-earth metal Y, Pr, or Gd (R), RIâ, and a 3d, 4d, or 5d element (Z) at 750-1,000°C in sealed Nb containers. New PrâIââZ (SCâClââN-type) phases are obtained for Z = Cu, Ru, Rh, Pd, Re, Os, Ir, and Pt. New GdâIââZ phases occur for

Martin W. Payne; John D. Corbett

1990-01-01

213

Rare earth element geochemistry of massive sulfides-sulfates and gossans on the Southern Explorer Ridge  

Microsoft Academic Search

Massive sulfide-sulfate deposits on the Southern Explorer Ridge were analyzed for 14 rare earth elements (REE) by a modified inductively coupled plasma-mass spectrometric technique that included a correction for high Ba content. Bulk samples of finely intermixed sulfides, sulfate, and amorphous silica contain ΣREE concentrations of ⤠6 ppm. REE patterns range from (1) strongly enriched in light REE with

Timothy J. Barrett; Ian Jarvis; Kym E. Jarvis

1990-01-01

214

Seawater rare-earth element patterns preserved in apatite of Pennsylvanian conodonts?  

Microsoft Academic Search

Past workers have used rare-earth element patterns recorded in biogenic apatite as proxies for original seawater chemistry. To explore the potency of this approach, we analyzed Pennsylvanian conodonts from limestones, gray shales, and black shales of the Fort Scott and Pawnee formations (Desmoinesian) and Swope and Dennis formations (Missourian) in Kansas, Missouri, and Iowa, U.S.A. Analysis of individual platform conodonts

Camomilia A. Bright; Anna M. Cruse; Timothy W. Lyons; Kenneth G. MacLeod; Michael D. Glascock; Raymond L. Ethington

2009-01-01

215

Cathodoluminescence of synthetic (doped with rare-earth elements) and natural anhydrites  

Microsoft Academic Search

In order to interpret cathodoluminescence (CL) spectra of natural anhydrites, synthetic crystals were indirectly obtained by precipitation of gypsum from solutions containing doping rare-earth elements (REE), and by transformation into anhydrite by dehydration at 800°C during 3 h. Analyses by ICP-MS of several anhydrites obtained from solutions containing 130 ppm of REE clearly showed that light REE (LREE) can be

A. Baumer; Ph. Blanc; F. Cesbron; D. Ohnenstetter

1997-01-01

216

A new highT(c) oxide superconductor without a rare earth element  

Microsoft Academic Search

A new high-T(c) oxide superconductor of the Bi-Sr-Ca-Cu-O system without any rare earth element was discovered. The oxide BiSrCaCu2O(x) has T(c) of about 105 K, higher than that of YBa2Cu3O7 by more than 10 K. In this oxide, the coexistence of Sr and Ca is necessary to obtain high T(c).

Hiroshi Maeda; Yoshiaki Tanaka; Masao Fukutomi; Toshihisa Asano

1988-01-01

217

Rare earth and high field strength element partitioning between iron-rich clinopyroxenes and felsic liquids  

Microsoft Academic Search

Rare earth elements are commonly assumed to substitute only for Ca in clinopyroxene because of the similarity of ionic radii\\u000a for REE3+ and Ca2+ in eightfold coordination. The assumption is valid for Mg-rich clinopyroxenes for which observed mineral\\/melt partition coefficients\\u000a are readily predicted by the lattice strain model for substitution onto a single site (e.g., Wood and Blundy 1997). We

P. H. OlinJ; J. A. Wolff

2010-01-01

218

The exact solution of Stokes' second problem including start-up process with fractional element  

NASA Astrophysics Data System (ADS)

The start-up process of Stokes’ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady oscillation. Exact solutions are obtained by using Laplace transform and Fourier transform. It is found that the relationship between the first peak value and the one of equal-amplitude oscillations depends on the distance from the plate. The amplitude decreases for increasing frequency and increasing distance.

Hu, Kaixin; Zhu, Keqin

2009-10-01

219

Transport of rare earth element-tagged soil particles in response to thunderstorm runoff.  

PubMed

The downslope transport of rare earth element-tagged soil particles remobilized during a spring thunderstorm was studied on both a natural prairie and an agricultural field in southwestern Iowa (U.S.A.). A technique was developed for tagging natural soils with the rare earth elements Eu, Tb, and Ho to approximately 1,000 ppm via coprecipitation with MnO2. Tagged material was replaced in target locations; surficial soil samples were collected following precipitation and runoff; and rare earth element concentrations were determined by inductively coupled plasma mass spectrometry. Diffusion and exponential models were applied to the concentration-distance data to determine particle transport distances. The results indicate that the concentration-distance data are well described by the diffusion model, butthe exponential model does not simulate the rapid drop-off in concentrations near the tagged source. Using the diffusion model, calculated particle transport distances at all hillside locations and at both the cultivated and natural prairie sites were short, ranging from 3 to 73 cm during this single runoff event. This study successfully demonstrates a new tool for studying soil erosion. PMID:11529577

Matisoff, G; Ketterer, M E; Wilson, C G; Layman, R; Whiting, P J

2001-08-15

220

Evaluating rare earth element availability: a case with revolutionary demand from clean technologies.  

PubMed

The future availability of rare earth elements (REEs) is of concern due to monopolistic supply conditions, environmentally unsustainable mining practices, and rapid demand growth. We present an evaluation of potential future demand scenarios for REEs with a focus on the issue of comining. Many assumptions were made to simplify the analysis, but the scenarios identify some key variables that could affect future rare earth markets and market behavior. Increased use of wind energy and electric vehicles are key elements of a more sustainable future. However, since present technologies for electric vehicles and wind turbines rely heavily on dysprosium (Dy) and neodymium (Nd), in rare-earth magnets, future adoption of these technologies may result in large and disproportionate increases in the demand for these two elements. For this study, upper and lower bound usage projections for REE in these applications were developed to evaluate the state of future REE supply availability. In the absence of efficient reuse and recycling or the development of technologies which use lower amounts of Dy and Nd, following a path consistent with stabilization of atmospheric CO(2) at 450 ppm may lead to an increase of more than 700% and 2600% for Nd and Dy, respectively, over the next 25 years if the present REE needs in automotive and wind applications are representative of future needs. PMID:22304002

Alonso, Elisa; Sherman, Andrew M; Wallington, Timothy J; Everson, Mark P; Field, Frank R; Roth, Richard; Kirchain, Randolph E

2012-03-20

221

Toward understanding early Earth evolution: Prescription for approach from terrestrial noble gas and light element records in lunar soils  

PubMed Central

Because of the almost total lack of geological record on the Earth's surface before 4 billion years ago, the history of the Earth during this period is still enigmatic. Here we describe a practical approach to tackle the formidable problems caused by this lack. We propose that examinations of lunar soils for light elements such as He, N, O, Ne, and Ar would shed a new light on this dark age in the Earth's history and resolve three of the most fundamental questions in earth science: the onset time of the geomagnetic field, the appearance of an oxygen atmosphere, and the secular variation of an Earth–Moon dynamical system.

Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A.; Miura, Yayoi N.

2008-01-01

222

Study of speciation and size fractionation of trace element between soil solution, bog, river and lake within a boreal watershed (North Karelia, NW Russia) using fractional filtration  

NASA Astrophysics Data System (ADS)

This work is aimed at studying the evolution of migration forms of true dissolved compounds and colloidal entities using an integrated approach of molecular mass distribution and differences in the association of trace elements (TE) with organic matter (OM) or Fe colloids in the system soil water-bog-river-lake. Characterization of TE speciation with colloids during TE migration from the site of colloids origin (bog and soil solutions) towards the transit zone (river) and finally to the deposition, accumulation or transformation zone (lake) is a main fundamental task of this problem. The objects of study include a small stream watershed Vostochniy and the river Palayoki (North Karelia, Russia). The water samplings were performed in July and August 2008 and 2009 and included soil solution, nourishing bog, the middle part of the brook originated from the swamp, the mouth of the brook and the lake Zipringa. We sampled large volumes (50 - 100 liters), and we applied, directly in the in-field-installed "clean laboratory" the sequential frontal filtration and ultrafiltration of samples through the filters of progressively decreasing poresize 100, 20, 10, 5, 0.8, 0.4, 0.2 and 0.1 microns; 100 kDa (0.0065 micron), 10 kDa (0.003 micron) and 1 kDa (0.0014 micron). This allowed separation of organic matter, coarse and fine particulate matter and colloids. All filtrates and selected retentates were analyzed for a wide range of macro-and micronutrients using ICP-MS. In filtrates of the river water, a significant decrease of iron concentration occurred in the range of 5 micron to 0.22 micron and from 100 kDa to 1 kDa. For alkali and alkaline earth elements (Mg, K, Ca), as well as for Cu, Ni, Cr the concentrations changed after passing through the 10 kDa membrane. Na concentration remains constant in all filtrates. The filtrates of the soil solution are characterized by a significant decreases in Na, K, after 0.1 micron, Ca, Cu in the range of 0.22 micron - 100 kDa and Mg, Ni in the range of 0.1 micron - 100 kDa. The changing of REEs concentrations occurred in the fraction smaller than 100 kDa for river water and in the fraction larger than 100 kDa in the soil solution. Concerning the evolution of element concentration in the system "soil solution - nourishing bog - river - lake", the concentration of Ca and Mg increases (with a little decrease in the stage "the nourishing bog - the middle current - the mouth"), and the concentration of Cu, Ni, Cr, Ti, Al decreases (with a slight increase in the interval "the nourishing swamp - the middle current - the mouth). The lanthanides have a maximum of their concentration in the river mouth and the minimum in the lake. Concentration of Fe, Zn in the soil solution is an order of magnitude higher than in the river and lake water. The ratio Fe / Me (where Me = Al, Cu, Zn, Ni, Co, Cr, Mn) naturally decreases in the course of filtration, whereas the ratio of Fe to Ti increases in a series of consecutive filtrates of soil solution. These observations can be interpreted as a result of interplay between the processes of TE leaching from soil and peat, complexation with colloids in the lake water and microbiological transformation of colloids in the course of the river flow and in the lake water. Results of the present study allow straightforward evaluation of the transformation of TE colloidal status between the site of their origin, migration and consumption (deposition) The work is executed at a Russian Federal Property Fund and CNRS support (?? 08-05-00312_a, 07-05-92212-CNRS_a).

Ilina, Svetlana M.; Lapitsky, Sergey A.; Alekhin, Yuriy V.; Pokrovsky, Oleg S.; Viers, Jerome

2010-05-01

223

Fractions  

NSDL National Science Digital Library

This is an accessible, easy-to-read book introducing fractions. It can be downloaded in PowerPoint, Impress, and Flash formats. For struggling or non-readers the book can be read aloud in a variety of voices. All of the books on the Tar Heel Reader site can be used with the Intellikeys keyboard with a custom overlay, a touch screen, and/or 1-3 switches. The text and background colors can be modified for students with visual impairments.

Cowley, K.

2011-05-09

224

Bioleaching of rare earth and radioactive elements from red mud using Penicillium tricolor RM-10.  

PubMed

The aim of this work is to investigate biological leaching of rare earth elements (REEs) and radioactive elements from red mud, and to evaluate the radioactivity of the bioleached red mud used for construction materials. A filamentous, acid-producing fungi named RM-10, identified as Penicillium tricolor, is isolated from red mud. In our bioleaching experiments by using RM-10, a total concentration of 2% (w/v) red mud under one-step bioleaching process was generally found to give the maximum leaching ratios of the REEs and radioactive elements. However, the highest extraction yields are achieved under two-step bioleaching process at 10% (w/v) pulp density. At pulp densities of 2% and 5% (w/v), red mud processed under both one- and two-step bioleaching can meet the radioactivity regulations in China. PMID:23548400

Qu, Yang; Lian, Bin

2013-05-01

225

Separation method and yields of small quantities of rare earth elements  

NASA Astrophysics Data System (ADS)

The EMIS PARSIFAL was designed to purify very small quantities of radioactive isotopes. Yields are therefore an important component of the separations. The ionization is done in a thermoionization source or a plasma source, according to the physical properties of the concerned elements. For rare earth elements (REE), hydroxides are electrodeposited on a tantalum wire; for thermoionization, the wire is introduced in a tungsten crucible whose depth is linked to the boiling point of the element. Samples weigh between 0.2 and 0.9 mg. The crucible, heated at 3050°C by electron bombardment, gives REE yields from 20 to 40% and usually 50% for europium. The total beam intensity is about 5 × 10 -6 A and separations last from 2 to 20 hours until the whole sample is consumed.

Boulin, Y.; Juery, A.

1992-08-01

226

Behavior and Distribution of Heavy Metals Including Rare Earth Elements, Thorium, and Uranium in Sludge from Industry Water Treatment Plant and Recovery Method of Metals by Biosurfactants Application  

PubMed Central

In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90–100% using a precipitation method with alkaline solution.

Gao, Lidi; Kano, Naoki; Sato, Yuichi; Li, Chong; Zhang, Shuang; Imaizumi, Hiroshi

2012-01-01

227

Behavior and distribution of heavy metals including rare Earth elements, thorium, and uranium in sludge from industry water treatment plant and recovery method of metals by biosurfactants application.  

PubMed

In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90-100% using a precipitation method with alkaline solution. PMID:22693485

Gao, Lidi; Kano, Naoki; Sato, Yuichi; Li, Chong; Zhang, Shuang; Imaizumi, Hiroshi

2012-01-01

228

Rare earth elements recycling from waste phosphor by dual hydrochloric acid dissolution.  

PubMed

This paper is a comparative study of recycling rare earth elements from waste phosphor, which focuses on the leaching rate and the technical principle. The traditional and dual dissolution by hydrochloric acid (DHA) methods were compared. The method of dual dissolution by hydrochloric acid has been developed. The Red rare earth phosphor (Y0.95Eu0.05)2O3 in waste phosphor is dissolved during the first step of acid leaching, while the Green phosphor (Ce0.67Tb0.33MgAl11O19) and the Blue phosphor (Ba0.9Eu0.1MgAl10O17) mixed with caustic soda are obtained by alkali sintering. The excess caustic soda and NaAlO2 are removed by washing. The insoluble matter is leached by the hydrochloric acid, followed by solvent extraction and precipitation (the DHA method). In comparison, the total leaching rate of the rare earth elements was 94.6% by DHA, which is much higher than 42.08% achieved by the traditional method. The leaching rate of Y, Eu, Ce and Tb reached 94.6%, 99.05%, 71.45%, and 76.22%, respectively. DHA can decrease the consumption of chemicals and energy. The suggested DHA method is feasible for industrial applications. PMID:24681591

Liu, Hu; Zhang, Shengen; Pan, Dean; Tian, Jianjun; Yang, Min; Wu, Maolin; Volinsky, Alex A

2014-05-15

229

Improved provenance tracing of Asian dust sources using rare earth elements and selected trace elements for palaeomonsoon studies on the eastern Tibetan Plateau  

NASA Astrophysics Data System (ADS)

The Asian Monsoon forms an important part of the earth's climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace elemental (Sc, Y, Th and the rare earth elements) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai-Tibetan Plateau) dust sources. Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle REE relative to the upper continental crust and average shale but the Thar desert has a REE signature distinctly different from all other dust sources. There are significant differences in major, trace and REE compositions between the coarse and fine fractions of the surface sands, with the finest <4 ?m fraction enriched in Al 2O 3, Fe 2O 3, MnO, MgO and K 2O and the <32 ?m fractions in Sc, Y, Th and the REE relative to the coarse fractions. The <4 ?m fraction best represents the bulk REE geochemistry of the samples. The provenance tracers Y/?REE, La/Er, La/Gd, Gd/Er, La/Yb, Y/Tb, Y/La, Y/Nd and to a certain extent the europium anomaly Eu/Eu ? (all REE normalized to post-Archean Australian shale, PAAS) are particle size-independent tracers, of which combinations of Y/?REE, La/Yb, Y/Tb, Y/La and Eu/Eu ? can be used to distinguish the Thar desert, the Chinese deserts, the Chinese loess plateau and the Tibetan soils. Their independence upon grain size means that these tracers can be applied to the long-range provenance tracing of Asian dust even when only bulk samples are available in the source region. Combinations of La/Th, Y/Tb, Y/?REE, Sc/La and Y/Er distinguish the Tibetan soils from the Chinese loess plateau and the Chinese deserts. La/Th and notably Th/?REE isolate the signature of the Badain Juran desert and the combination of Sc/La and Y/Er that of the Taklamakan desert. The similarity in all trace and REE-based provenance tracers between the northern Qaidam basin and Tengger desert suggests that these two deposits may have a common aeolian source.

Ferrat, Marion; Weiss, Dominik J.; Strekopytov, Stanislav; Dong, Shuofei; Chen, Hongyun; Najorka, Jens; Sun, Youbin; Gupta, Sanjeev; Tada, Ryuji; Sinha, Rajiv

2011-11-01

230

Rare-earth elements in Egyptian granite by instrumental neutron activation analysis.  

PubMed

The mobilization of rare-earth elements (REEs) in the environment requires monitoring of these elements in environmental matrices, in which they are mainly present at trace levels. The similarity in REEs chemical behavior makes the separate determination of each element by chemical methods difficult; instrumental neutron activation analysis (INAA), based on nuclear properties of the elements to be determined, is a method of choice in trace analysis of REEs and related elements. Therefore, INAA was applied as a sensitive nondestructive analytical tool for the determination of REEs to find out what information could be obtained about the REEs of some Egyptian granite collected from four locations in Aswan area in south Egypt as follows wadi El-Allaqi, El-Shelal, Gabel Ibrahim Pasha and from Sehyel Island and to estimate the accuracy, reproducibility and detection limit of NAA method in case of the given samples. The samples were properly prepared together with standards and simultaneously irradiated in a neutron flux of 7 x 10(11)n/cm(2)s in the TRIGA Mainz research reactor facilities. The following elements have been determined: La, Ce, Nd, Sm, Eu, Yb and Lu. The gamma spectra was collected by HPGe detector and the analysis was done by means of computerized multichannel analyzer. The X-ray fluorescence (XRF) was also used. PMID:17208446

El-Taher, A

2007-04-01

231

Surface kinetic model for isotopic and trace element fractionation during precipitation of calcite from aqueous solution  

SciTech Connect

A surface reaction kinetic model is developed for predicting Ca isotope fractionation and metal/Ca ratios of calcite as a function of rate of precipitation from aqueous solution. The model is based on the requirements for dynamic equilibrium; i.e. proximity to equilibrium conditions is determined by the ratio of the net precipitation rate (R{sub p}) to the gross forward precipitation rate (R{sub f}), for conditions where ionic transport to the growing crystal surface is not rate-limiting. The value of R{sub p} has been experimentally measured under varying conditions, but the magnitude of R{sub f} is not generally known, and may depend on several factors. It is posited that, for systems with no trace constituents that alter the surface chemistry, R{sub f} can be estimated from the bulk far-from-equilibrium dissolution rate of calcite (R{sub b} or k{sub b}), since at equilibrium R{sub f} = R{sub b}, and R{sub p} = 0. Hence it can be inferred that R{sub f} {approx} R{sub p} + R{sub b}. The dissolution rate of pure calcite is measureable and is known to be a function of temperature and pH. At given temperature and pH, equilibrium precipitation is approached when R{sub p} (= R{sub f} - R{sub b}) << R{sub b}. For precipitation rates high enough that R{sub p} >> R{sub b}, both isotopic and trace element partitioning are controlled by the kinetics of ion attachment to the mineral surface, which tend to favor more rapid incorporation of the light isotopes of Ca and discriminate weakly between trace metals and Ca. With varying precipitation rate, a transition region between equilibrium and kinetic control occurs near R{sub p} {approx} R{sub b} for Ca isotopic fractionation. According to this model, Ca isotopic data can be used to estimate R{sub f} for calcite precipitation. Mechanistic models for calcite precipitation indicate that the molecular exchange rate is not constant at constant T and pH, but rather is dependent also on solution saturation state and hence R{sub p}. Allowing R{sub b} to vary as R{sub p}{sup 1/2}, consistent with available precipitation rate studies, produces a better fit to some trace element and isotopic data than a model where R{sub b} is constant. This model can account for most of the experimental data in the literature on the dependence of {sup 44}Ca/{sup 40}Ca and metal/Ca fractionation in calcite as a function of precipitation rate and temperature, and also accounts for {sup 18}O/{sup 16}O variations with some assumptions. The apparent temperature dependence of Ca isotope fractionation in calcite may stem from the dependence of R{sub b} on temperature; there should be analogous pH dependence at pH < 6. The proposed model may be valuable for predicting the behavior of isotopic and trace element fractionation for a range of elements of interest in low-temperature aqueous geochemistry. The theory presented is based on measureable thermo-kinetic parameters in contrast to models that equire hyper-fast diffusivity in near-surface layers of the solid.

DePaolo, D.

2010-10-15

232

Trace Element Partitioning Between Earths Lower Mantle Minerals and Iron Alloy Melts  

NASA Astrophysics Data System (ADS)

The physical conditions (pressure-temperature-oxygen fugacity) and iron alloy compositions involved in the formation of Earths core are relatively poorly constrained. Current geochemical core formation models rely heavily on arguments related to how trace elements are distributed between metal and silicate during metal segregation. Hypotheses concerning the timing of Earths accretion and core segregation also require knowledge of metal-silicate partition coefficients for parent and daughter isotopes in key isotopic systems (e.g., W-Hf, U-Pb). Many studies (e.g., Righter, Ann Rev Earth Planet Sci 2003) have focused on metal melt - silicate melt partitioning at upper mantle and transition zone pressures (P < 25 GPa) and high temperatures. In contrast, little is known about the partitioning of trace elements between metals and lower mantle minerals and melts, even though the later stages of core formation, characterised by high-energy processes related to collisions of Mars-sized objects, likely involved liquid iron alloys percolating through a solid or molten lower mantle matrix. We will present results of a systematic study of the distribution of trace elements between lower mantle minerals (Ca and Mg perovskite, and ferropericlase) and a range of iron alloy melts, to assess the redistribution of trace elements as metallic melts percolate through the lower mantle. Experiments are performed using a 10/3.5 assembly in a conventional Walker-type multi-anvil press (P < 26 GPa), and using a 7/2 assembly in a spherically-constrained multi-anvil press with sintered diamond pressure-transmitting cubes (P > 30 GPa). Starting materials include end-member silicates (wollastonite, enstatite), MgO, and Fe-light element (S, Si) mixtures. Trace elements added include slightly siderophile (Mn, V, Cr), moderately siderophile (P, W, Co, Ni, Mo) and highly siderophile elements, as well as key parent-daughter pairs, and run products are analysed by laser ablation ICP-MS. Implications of our data for core formation models will be discussed.

van Westrenen, W.; Schmidt, M.; Günther, D.; Stewart, A.

2004-12-01

233

Coronal sources, elemental fractionation, and release mechanisms of heavy ion dropouts in the solar wind  

NASA Astrophysics Data System (ADS)

The elemental abundances of heavy ions (m > He) in the solar wind provide information concerning physical processes occurring in the corona. Additionally, the charge state distributions of these heavy ions are sensitive to the temperature profiles of their respective source regions in the corona. Both the abundances and charge states become set within a few solar radii and propagate unchanged throughout the heliosphere, regardless of turbulence, propagation effects, and local heating. Therefore, heavy ions yield in-situ evidence of an environment inaccessible to spacecraft and traditionally only observed via spectroscopy. Heavy ion dropouts are a relatively new class of solar wind events. Their origins lie in large, closed coronal loops where processes such as gravitational settling dominate and can cause a mass-dependent fractionation pattern. In this study we consider and attempt to answer three fundamental questions concerning heavy ion dropouts: (1) Where are the source loops located in the large scale corona?, (2) How does the interplay between coronal processes influence the end elemental abundances?, and (3) What are the most probable release mechanisms?. We begin by analyzing the temporal and spatial variability of heavy ion dropouts and their correlation with heliospheric plasma and magnetic structures. Next we investigate the ordering of the elements inside dropouts with respect to mass, charge state, and First Ionization Potential. Finally, we consider the prevailing solar wind theories and the processes they posit that may be responsible for the release of coronal plasma into interplanetary space.

Weberg, M. J.; Lepri, S. T.; Zurbuchen, T.

2013-12-01

234

Experimental investigations of trace element fractionation in iron meteorites. II - The influence of sulfur  

NASA Technical Reports Server (NTRS)

The partitioning of Ir, Ge, Ga, W, Cr, Au, P, and Ni between solid metal and metallic liquid is investigated as a function of temperature and the S-concentration of the metallic liquid. The partition coefficients for siderophile elements, such as Ir, W, Ga, and Ge, are found to increase by factors of 10-100 as the S-concentration of the metallic liquid increases from 0-30 wt percent. Partition coefficients for other siderophile elements, such as Ni, Au, and P, increase by factors of only 2-3. In contrast, a decrease is seen in the partition coefficients for the more chalcophile element Cr. These experimentally determined coefficients are used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of Ni, P, Au, and Ir during the magmatic evolution of groups IIAB, IIIAB, IVA and IVB iron meteorites. The mean S-concentration for each group increases in the order IVB, IVA, IIIAB, IIAB, which is in accordance with cosmochemical prediction. However, the geochemical behavior of Ge, Ga, W, and Cr cannot be reproduced in an internally consistent way. It is concluded that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed.

Jones, J. H.; Drake, M. J.

1983-01-01

235

Experimental Simulations of Core Formation at High Pressure and Temperature: Constraints on Candidate Light Elements in the Earth's Core  

Microsoft Academic Search

Although a number of candidate light elements have been suggested to alloy with Fe in the Earth's core, there is no general consensus on which is the most predominant, due to the lack of knowledge about this portion of the Earth. We have carried out experimental simulations on possible core formation processes by examining the behavior of iron in the

T. Uchida; Y. Wang; M. L. Rivers; S. R. Sutton

2002-01-01

236

Characterizing ablation and aerosol generation during elemental fractionation on absorption modified lithium tetraborate glasses using LA-ICP-MS  

Microsoft Academic Search

The influence of sample matrix composition, absorption behavior and laser aerosol particle size distribution on elemental fractionation in laser ablation inductively coupled plasma mass spectrometry was studied for nanosecond laser ablation at a wavelength of 266 nm. To this end, lithium tetraborate glass samples with different iron oxide contents and trace amounts of a group of 11 elements were prepared synthetically.

Peter Weis; Horst P. Beck; Detlef Günther

2005-01-01

237

Selective liquid chromatographic separation of yttrium from heavier rare earth elements using acetic acid as a novel eluent.  

PubMed

One of the major difficulties in the rare earth elements separation is purification of yttrium from heavy rare earth elements. Thus, an HPLC method using acetic acid as novel eluent was explored for selective separation of yttrium form the heavy rare earth elements. When acetic acid is used as a mobile phase yttrium eluted with the lighter lanthanides. This is contrary to its relative position amongst heavier lanthanides when eluents commonly used for separation of rare earth elements were employed. The shift in elution position of yttrium with acetic acid as eluent may reflect a relatively lower stability constant of the yttrium-AcOH complex (in the same order as for the lighter lanthanides) compared to the corresponding AcOH complexes with heavy lanthanides, enabling selective separation of yttrium from the latter. The method was successfully used for selective separation of yttrium in mixed rare earth sample containing about 80% of yttrium and about 20% of heavy rare earth oxides. Thus, the use of AcOH as eluent is an effective approach for separating and determining the trace amounts of heavy rare earth elements in large amounts of yttrium matrix. Separation was performed on C18 column by running appropriate elution programs. The effluent from the column was monitored with diode array detector at absorbance wavelength of 658nm after post column derivatization with Arsenazo III. PMID:23932372

Kifle, Dejene; Wibetoe, Grethe

2013-09-13

238

Comparison of the partitioning behaviours of yttrium, rare earth elements, and titanium between hydrogenetic marine ferromanganese crusts and seawater  

Microsoft Academic Search

In order to evaluate details of the partitioning behaviours of Y, rare earth elements (REEs), and Ti between inorganic metal oxide surfaces and seawater, we studied the distribution of these elements in hydrogenetic marine ferromanganese (Fe-Mn) crusts from the Central Pacific Ocean. Nonphosphatized Fe-Mn crusts display shale-normalized rare earths and yttrium (REYSN) patterns (Y inserted between Dy and Ho) that

Michael Bau; Andrea Koschinsky; Peter Dulski; James R. Hein

1996-01-01

239

Determination of rare earth elements and thorium in britholite ore by energy dispersive X-ray fluorescence spectrometry  

Microsoft Academic Search

A radioisotope-excited X-ray fluorescence technique is applied for the determination of thorium and rare earth elements in britholite ore from Canada. An annular source of57Co is employed for excitation of characteristic K X-rays of thorium and rare earth elements. The peak ratios of lanthanides were used to remove the difficulties because of overlapping lines at the 33–50 keV energy region.

N. Efe; S. Akman; P. Arikan

1987-01-01

240

Investigation of biological activity of fine fraction of lunar surface material returned to earth by the Luna 16 automatic station  

NASA Technical Reports Server (NTRS)

The biological action of a sample of lunar surface material returned to earth by the Luna 16 automatic station from a new region of the mare surface on male white mice was studied. The condition and behavior of the animals were observed; the intensity of their oxygen consumption was recorded, and motor activity of the muscles, leucocyte and erythrocytes counts in the peripheral blood, and the activity of whole blood chloinesterase were determined. Experimental results showed that the tested doses of the fine fraction of the lunar surface material from the Sea of Fertility were virtually innocuous for white mice.

Kustov, V. V.; Ostapenko, O. F.; Petrukhin, V. G.

1974-01-01

241

Systematics of metal-silicate partitioning for many siderophile elements applied to Earth’s core formation  

NASA Astrophysics Data System (ADS)

Superliquidus metal-silicate partitioning was investigated for a number of moderately siderophile (Mo, As, Ge, W, P, Ni, Co), slightly siderophile (Zn, Ga, Mn, V, Cr) and refractory lithophile (Nb, Ta) elements. To provide independent constrains on the effects of temperature, oxygen fugacity and silicate melt composition, isobaric (3 GPa) experiments were conducted in piston cylinder apparatus at temperature between 1600 and 2600 °C, relative oxygen fugacities of IW-1.5 to IW-3.5, and for silicate melt compositions ranging from basalt to peridotite. The effect of pressure was investigated through a combination of piston cylinder and multi-anvil isothermal experiments between 0.5 and 18 GPa at 1900 °C. Oxidation states of siderophile elements in the silicate melt as well as effect of carbon saturation on partitioning are also derived from these results. For some elements (e.g. Ga, Ge, W, V, Zn) the observed temperature dependence does not define trends parallel to those modeled using metal-metal oxide free energy data. We correct partitioning data for solute interactions in the metallic liquid and provide a parameterization utilized in extrapolating these results to the P- T- X conditions proposed by various core formation models. A single-stage core formation model reproduces the mantle abundances of several siderophile elements (Ni, Co, Cr, Mn, Mo, W, Zn) for core-mantle equilibration at pressures from 32 to 42 GPa along the solidus of a deep peridotitic magma ocean (˜3000 K for this pressure range) and oxygen fugacities relevant to the FeO content of the present-day mantle. However, these P- T- fO 2 conditions cannot produce the observed concentrations of Ga, Ge, V, Nb, As and P. For more reducing conditions, the P- T solution domain for single stage core formation occurs at subsolidus conditions and still cannot account for the abundances of Ge, Nb and P. Continuous core formation at the base of a magma ocean at P- T conditions constrained by the peridotite liquidus and fixed fO 2 yields concentrations matching observed values for Ni, Co, Cr, Zn, Mn and W but underestimates the core/mantle partitioning observed for other elements, notably V, which can be reconciled if accretion began under reducing conditions with progressive oxidation to fO 2 conditions consistent with the current concentration of FeO in the mantle as proposed by Wade and Wood (2005). However, neither oxygen fugacity path is capable of accounting for the depletions of Ga and Ge in the Earth's mantle. To better understand core formation, we need further tests integrating the currently poorly-known effects of light elements and more complex conditions of accretion and differentiation such as giant impacts and incomplete equilibration.

Siebert, Julien; Corgne, Alexandre; Ryerson, Frederick J.

2011-03-01

242

Rare-Earth Elements in Lighting and Optical Applications and Their Recycling  

NASA Astrophysics Data System (ADS)

Rare-earth elements (REEs) are used in lighting and optical applications to enable color and light adjustment, miniaturization, and energy efficiency. Common applications of REEs include phosphors for light-emitting diodes, lasers, and electronic video displays. This article reviews how REEs are widely used in these applications. However, supply constraints, including rising prices, environmental concerns over mining and refining processes, and China's control over the supply of the vast majority of REEs, are of concern for manufacturers. In view of these supply constraints, this article discusses ways for manufacturers of lighting and optical devices to identify potential substitutes and recycling methods for REEs.

Song, Xin; Chang, Moon-Hwan; Pecht, Michael

2013-10-01

243

Rare-earth elemental analysis of banded iron-formations by instrumental neutron activation analysis  

Microsoft Academic Search

Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated\\u000a by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux\\u000a of 5.1·1016 m?2·s?1, 1.0·1015 m?2·s?1 and 3.7·1015 m?2s?1, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector.\\u000a Ten rare-earth elements,

P. K. Nayak; B. Wierczinski; S. Lahiri

2008-01-01

244

The mobility of rare-earth elements during hydrothermal activity: A review  

Microsoft Academic Search

The mobility of the rare-earth elements (REE) during hydrothermal activities is increasingly documented. Geological and experimental\\u000a evidence suggests that REE may be mobile in solutions rich in F-, Cl-, HCO3\\u000a -, CO3\\u000a 2-, HPO4\\u000a 2-, PO4\\u000a 3-, or in combinations of the above ligands, even though little has been known about which ligand or which combination is most\\u000a effective in

Xiong Yongliang; Zhai Yusheng

1991-01-01

245

Effect of rare earth element additions on the impression creep of Sn–9Zn solder alloy  

Microsoft Academic Search

Creep behavior of the Sn–9Zn–RE alloys containing 0.1, 0.25 and 0.5 wt.% rare earth (RE) elements was studied by impression\\u000a testing and compared to that of the eutectic Sn–9Zn alloy. The tests were carried out under constant punching stress in the\\u000a range 40–135 MPa and at temperatures in the range 298–420 K. Results showed that for all loads and temperatures, Sn–9Zn–0.25RE\\u000a had the

R. Mahmudi; A. R. Geranmayeh; B. Zahiri; M. H. Marvasti

2010-01-01

246

The determination of trace elements in crude oil and its heavy fractions by atomic spectrometry  

NASA Astrophysics Data System (ADS)

A literature review on the determination of trace elements in crude oil and heavy molecular mass fractions (saturates, aromatics, resins and asphaltenes) by ICP-MS, ICP OES and AAS is presented. Metal occurrences, forms and distributions are examined as well as their implications in terms of reservoir geochemistry, oil refining and environment. The particular analytical challenges for the determination of metals in these complex matrices by spectrochemical techniques are discussed. Sample preparation based on ashing, microwave-assisted digestion and combustion decomposition procedures is noted as robust and long used. However, the introduction of non-aqueous solvents and micro-emulsions into inductively coupled plasmas is cited as a new trend for achieving rapid and accurate analysis. Separation procedures for operationally defined fractions in crude oil are more systematically applied for the observation of metal distributions and their implications. Chemical speciation is of growing interest, achieved by the coupling of high efficiency separation techniques (e.g., HPLC and GC) to ICP-MS instrumentation, which allows the simultaneous determination of multiple organometallic species of geochemical and environmental importance.

Duyck, Christiane; Miekeley, Norbert; Porto da Silveira, Carmem L.; Aucélio, Ricardo Q.; Campos, Reinaldo C.; Grinberg, Patrícia; Brandão, Geisamanda P.

2007-09-01

247

An approach to monitor the fraction of elemental carbon in the ultrafine aerosol  

NASA Astrophysics Data System (ADS)

Attempts were made to measure the fraction of elemental carbon (EC) in ultrafine aerosol by modifying an Ambient Carbonaceous Particulate Monitor (ACPM, R&P 5400). The main modification consisted in placing a quartz filter in one of the sampling lines of this dual-channel instrument. With the filter all aerosol and EC contained in it is collected, while in the other line of the instrument the standard impactor samples only particles larger than 0.14 ?m. The fraction of EC in particles smaller than 0.14 ?m is derived from the difference in concentration as measured via the two sampling lines. Measurements with the modified instrument were made at a suburban site in Amsterdam, The Netherlands. An apparent adsorption artefact, which could not be eliminated by the use of denuders, precluded meaningful evaluation of the data for total carbon. Blanks in the measurements of EC were negligible and the EC data were hence further evaluated. We found that the concentration of EC obtained via the channel with the impactor was systematically lower than that in the filter-line. The average ratio of the concentrations was close to 0.6, which indicates that approximately 40% of the EC was in particles smaller than 0.14 ?m. Alternative explanations for the difference in the concentration in the two sampling lines could be excluded, such as a difference in the extent of oxidation. This should be a function of loading, which is not the case. Another reason for the difference could be that less material is collected by the impactor due to rebound, but such bounce of aerosol is very unlikely in The Netherlands due to co-deposition of abundant deliquesced and thus viscous ammonium compounds. The conclusion is that a further modification to assess the true fraction of ultrafine EC, by installing an impactor with cut-off diameter at 0.1 ?m, would be worth pursuing.

ten Brink, Harry; Hoek, Gerard; Khlystov, Andrey

248

Environmental impact of toxic elements in red mud studied by fractionation and speciation procedures.  

PubMed

Aluminum (Al) is mostly produced from bauxite ore, which contains up to 70% of Al(2)O(3) (alumina). Before alumina is refined to aluminum metal, it is purified by hot alkaline extraction. As a waste by-product red mud is formed. Due to its high alkalinity and large quantities, it represents a severe disposal problem. In Kidri?evo (Slovenia), red mud was washed with water before disposal, and after drying, covered with soil. In Ajka (Hungary), the red mud slurry was collected directly in a containment structure, which burst caused a major accident in October 2010. In the present work the environmental impact of toxic elements in red mud from Kidri?evo and Ajka were evaluated by applying a sequential extraction procedure and speciation analysis. The predominant red mud fraction was the insoluble residue; nevertheless, environmental concern was focused on the highly mobile water-soluble fraction of Al and Cr. Al in the water-soluble Ajka mud fraction was present exclusively in form of toxic [Al(OH)(4)](-), while Cr existed in its toxic hexavalent form. Comparative assessment to red mud from Kidri?evo (Slovenia) with a lower alkalinity (pH 9) with that from Ajka demonstrated significantly lower Al solubility and the presence of only trace amounts of Cr(VI), confirming that disposal of neutralized mud is environmentally much more acceptable and carries a smaller risk of ecological accidents. Since during the Ajka accident huge amounts of biologically available Al and moderate Cr(VI) concentrations were released into the terrestrial and aquatic environments, monitoring of Al and Cr(VI) set free during remedial actions at the contaminated site is essential. Particular care should be taken to minimize the risk of release of soluble Al species and Cr(VI) into water supplies and surface waters. PMID:22542238

Mila?i?, Radmila; Zuliani, Tea; Š?an?ar, Janez

2012-06-01

249

The light element component of the Earth’s core: Constraints from in situ X-Radiography in the LHDAC  

NASA Astrophysics Data System (ADS)

The light element budget of the Earth’s core depends in part on the high-pressure melting relations of the relevant iron rich binary systems. Candidate alloying elements include H, C, O, Si and S, due to their cosmochemical abundance. Many of these systems are known to contain eutectic points, the temperatures and compositions of which are critical to reconstructing the phase relations of these systems. Thus far most studies reporting the composition of eutectic liquids depend on ex situ analysis with a potential for systematic errors introduced by quench induced exsolution. To circumvent this issue we have developed an in situ technique for the determination of liquid compositions in iron-rich binary systems at simultaneous high-pressure and high-temperature conditions. Samples consist of Fe(1-x)O or FeS, surrounded by a ring of iron forming a ‘donut’ with a diameter of ~100?m and a thickness of ~20?m. Pressure is monitored by ruby fluorescence. The sample is heated at the boundary between the iron and light element compound using two 100 W IR lasers in a double-sided configuration at beamline 12.2.2 at the Advanced Light Source. Temperature is measured by spectroradiometry. Before, during and after melting, X-radiographic images of the sample are taken by shining a defocused beam of synchrotron X-rays through the sample and onto a CdWO4 phosphor. The visible light from the phosphor is then focused onto a high resolution CCD, where absorption contrast images are recorded. The absorption of the molten region is then determined, and it’s composition calculated by comparison to the absorption of the two solid end members. In previous work we measured the composition of the Fe-FeS eutectic to 20 GPa and the Fe-Fe3C eutectic to 44 GPa [1,2]. Further, we saw no discernible solubility of oxygen in liquid iron up to 43 GPa [1]. Here we extend the data for sulfur up to 70 GPa and for oxygen up to 63 GPa. Our new sulfur data fit well with previous studies at lower pressure, and suggest that the sulfur content of the eutectic is tending to ~15wt% with increasing pressure. In the Fe-FeO system, upon reaching the Fe-FeO eutectic temperature (indicated by a plateau in the power-temperature function), no evidence of a melt was seen within the absorption contrast images. Only when the temperature was raised above this first plateau to a second plateau, representing the melting point of FeO did a ‘ledge’ appear in the absorption contrast image, suggesting the presence of a liquid with a composition intermediate between Fe and FeO. Further, the composition of this ledge was pressure insensitive, and close to a 50:50 mix of Fe and FeO. We interpret these results as the formation of a eutectic melt with an oxygen content below the detection limit (~1 wt%), followed by melting of the FeO end-member and the subsequent mixing of the two liquid phases. These results suggest that the solubility of oxygen remains below ~1wt% beyond 60 GPa, in contradiction with several recent studies [3]. [1] Walker, D., et al. Chem Geol., 2008. [2] Lord, O. T., et al. EPSL, 2009. [3] Seagle, C. T., et al. EPSL, 2008.

Lord, O. T.; Walter, M. J.; Walker, D.; Clark, S. M.

2009-12-01

250

The search for fractional charge elemental particles and very massive particles in bulk matter  

SciTech Connect

The authors describe their ongoing work on, and future plans for, searches in bulk matter for fractional charge elementary particles and very massive elementary particles. Their primary interest is in searching for such particles that may have been produced in the early universe and may be found in the more primeval matter available in the solar system: meteorites, material from the moon's surface, and certain types of ancient terrestrial rocks. In the future the authors are interested in examining material brought back by sample return probes from asteroids. The authors will describe their experimental methods that are based on new modifications of the Millikan liquid drop technique and modern technology: micromachining, CCD cameras, and desktop computers. Extensions of the experimental methods and technology allow searches for very massive charged particles in primeval matter; particles with masses greater than 1,013 GeV. In the first such searches carried out on earth there will be uncertainties in the mass search range. Therefore the authors will also discuss the advantages of eventually carrying out such searches directly on an asteroid.

Perl, M.

2000-01-12

251

Contrasting behaviour of anthropogenic gadolinium and natural rare earth elements in estuaries and the gadolinium input into the North Sea  

NASA Astrophysics Data System (ADS)

All major rivers in northwestern Germany that flow into the North Sea, including the Weser River, display rare earth element (REE) patterns with large positive gadolinium (Gd) anomalies that indicate the presence of anthropogenic Gd derived from contrast agents used in magnetic resonance imaging. This microcontaminant cannot be removed by common sewage treatment technology and enters rivers and lakes with the discharge from waste water treatment plants. As elsewhere, a large fraction of the natural dissolved REE in the Weser River are associated with colloids. These colloids aggregate during mixing of freshwater and seawater in the low-salinity part of the Weser Estuary and the dissolved REE are partially removed from the river water together with the colloids. In marked contrast to the natural REE, the anthropogenic Gd behaves conservatively during this estuarine mixing and transits through the Weser Estuary almost unaffected. This indicates that the speciation of anthropogenic Gd is different from that of natural Gd and suggests a long environmental half-life of the anthropogenic Gd complexes used as contrast agents. The amount of anthropogenic Gd introduced into seawater via rivers is significant and produces anthropogenic positive Gd anomalies in coastal seawater. This is observed in the southwestern North Sea, off the coast of the East Frisian Islands, where anthropogenic Gd is mostly derived from the rivers Rhine and Thames. Its long environmental half-life and conservative estuarine behaviour suggest that anthropogenic Gd might be utilized as a pseudo-natural far-field tracer for truly dissolved riverine REE input into seawater and for discharge from waste water treatment plants and for sewage in river, ground and drinking water. The widespread distribution of anthropogenic Gd is an example of how the increasing use of "exotic" (ultra)trace elements in high-tech processes will in the future significantly hamper studies of the distribution and geochemical behaviour of such elements in natural systems.

Kulaks?z, Serkan; Bau, Michael

2007-08-01

252

Mineralogy and geochemistry of trace and Rare Earth Element from the Manaila massive sulphide deposit (Eastern Carpathians, Romania)  

NASA Astrophysics Data System (ADS)

Keywords: Eastern Carpathians, M?n?ila deposit, REE, trace elements, pyrite The present paper deal with the mineralogy and trace elements geochemistry of sulphide deposits from M?n?ila mine field located in NE area of Eastern Carpathians Mountains (Romania). The mineralization occurs within metamorphic rocks of Tulghe? terrane, part of Crystalline-Mezozoic zone of the Eastern Carpathians. The metamorphic rocks in M?n?ila area consist of felsic metavolcanics rocks with quartzites and quartz-feldspathic rocks as prevailing types. The P-T metamorphic conditions are typical of greenschis facies with biotite and garnet (Mn-Grt) in mineral assemblage. The mineralogical study was performed using reflected light microscope and Scanning Electron Microscopy (SEM) methods. Thus, the both methods show that the main sulphides minerals are represented by pyrite and chalcopyrite, being followed by sphalerite, galena and little amount of Cu sulphosalts (tetrahedrite and bournonite) and also by gangue minerals (quartz and carbonates). Pyrite occurs as large euhedral to subhedral grains in quartz and small rounded inclusion in chalcopyrite. The trace elements analysis was achieved on whole-rock samples and involved the determination of REE, LIL (Rb, Ba, Sr) and HFS (Y, Zr, Hf, U, Th, Nb, Ta) by ICP-MS method. The concentration of LIL and HFS trace elements in mineralized rocks decrease as follows: Ba > Bi > As > Sb > Co > Ga > Ni > Cd. Even if the barium contents in M?n?ila ore is high, baritina (BaSO4) was not identified throught the mineralogical analyses carried out so far. The total rare earth element content (REE) of the samples from M?n?ila range from 26.84 to 246.46 ppm. Chondrite - normalized REE patterns of the mineralized rocks show that the LREE are enriched in relation to the HREE. Also a positive Ce anomalies and negative Eu anomalies are present. Y/Ho and Zr/Hf ratios are close to the chondritic ratios indicating Charge-and-Radius-Controlled (CHARAC) behavior of these elements in pure silicate melts. The REE patterns of the ores are highly variable and do not appear to be related to the mineral compositions. This feature may reflect contributions from several factors involved in fluid formation, ore mineral deposition and post-depositional processes. The lack of a relation between major mineral composition and REE patterns suggests complex REE fractionation processes during the ore formation. This work was supported by the European Social Fund in Romania, under the responsibility of the Managing Authority for the Sectoral Operational Programme for Human Resources Development 2007-2013 (grant POSDRU/88/1.5/S/47646).

Moldoveanu, S.; Iancu, O. G.; Kasper, H. U.

2012-04-01

253

Behavior of rare earth and trace elements in Lake Tanganyika and its three major tributaries  

NASA Astrophysics Data System (ADS)

Water samples were collected, during the rainy and dry seasons 2003, from three major rivers and several locations of the Lake Tanganyika. They were directly filtered (0.45 im pore size) into pre-washed polyethylene bottles, and acidified at pH 2. Finnigan Element 2 high resolution (HR)-IC-MPS was used to measure trace and rare earth elements (REE) concentrations under clean laboratory conditions, and (115In) was used as an internal standard. Because of the close relationship between light rare earth element (LREE) and Fe, riverine REE of the three were used to study the process trace element scavenging by Fe oxyhydroxides in three different two sub-basins of the lake. This confirmed by the significant positive correlation between Nd and Fe. The vertical distribution of Fe and Mn oxides were also used to investigate removal and release of trace elements in the water column. The normalized lacustrine REE to their riverine counterpart showed a gradual removal of REE across the lake, which was in the order of LREE>MREE>HREE. Hence, the rivers are the sole source of the lacustrine REE abundance. Coincidence of Fe maxima with those of Ce anomalies and La indicates that trace element profiles are chiefly controlled by the coating of Fe oxyhydroxides through oxidation of Fe2+ to Fe3+ under high dissolved oxygen contents and pH and vice versa. Due to differences in hydrodynamics between the extreme ends of the lake (upwelling in the southern end during the dry season), high mixing between bottom water and surface was observed at the surface in the Southern Basin while the mixing occurred mainly between 40 m and 80 m depth in the Northern Basin. There was also a clear similarity between Ba and NO3- and PO43- profiles in the southern end of the lake, supporting the idea that deep anoxic water, rich in nutrients and trace elements, are bought the surface during this period of intensive upwelling. In conclusion, the surface water chemical compositions of Lake Tanganyika are controlled by fluvial inputs and the seasonal changes in hydrodynamics across the lake.

Sako, A.; Johnson, R.

2004-12-01

254

Earth Observatory Satellite system definition study. Report no. 5: System design and specifications. Part 1: Observatory system element specifications  

NASA Technical Reports Server (NTRS)

The performance, design, and quality assurance requirements for the Earth Observatory Satellite (EOS) Observatory and Ground System program elements required to perform the Land Resources Management (LRM) A-type mission are presented. The requirements for the Observatory element with the exception of the instruments specifications are contained in the first part.

1974-01-01

255

Rare earth elements in soils from selected areas on the Island of Hawaii  

SciTech Connect

Fifty soil samples for the wet, windward (east) side and dry, leeward (west) side of the Island of Hawaii were analyzed for La, Ce, Sm, Eu, Yb, and Lu by neutron activation/gamma-ray spectroscopic analysis. Data on concentrations in each sample are listed and analyzed statistically for soil samples collected from the western slope of Kohala Mountain, the western coastal plain of Mauna Kea, and the Northeastern coastal plain of Maunal Loa. Rare earth element (REE) concentrations are two to six times greater in soils from the western, dry side of the island, and good statistical correlation is exhibited among the samples for pairs of individual REEs. In the organic-rich soils of the east side, correlations are poor but are markedly improved when sample weights are adjusted for weight due to organic matter and water in soil colloids. If the mean compositions of selected rock samples from the Hawaii Reference Suite are representative of the compositions of the parent materials, REEs in the soils are moderately enriched (up to two times, based on oven-dry weights). Rare earth element concentrations in the island's western soils are as much as two times greater than the mean REE values of common sedimentary rocks worldwide; however, they are well within the concentration ranges of soils of continental origin. The eastern soils tend to have less La and Ce, but similar amounts of the middle and heavy REEs.

Barnard, W.M.; Halbig, J.B.

1985-07-01

256

Partitioning of platinum-group elements and Au between sulfide liquid and basalt and the origins of mantle-crust fractionation of the chalcophile elements  

NASA Astrophysics Data System (ADS)

The partitioning of platinum-group elements (PGE; Os, Ir, Ru, Rh, Pt, and Pd) and Au between sulfide melt and silicate melt (i.e., DPGEsul) exerts a critical control on the PGE composition of the Earth's crust and mantle, but previous estimates have been plagued by experimental uncertainties and vary through several orders of magnitude. Here we present direct experimental measurements of DPGEsul, based on in situ microanalysis of the sulfide and silicate melt, with values ranging from ˜4 × 105 (Ru) to ˜2-3 × 106 (Ir, Pt). Our measurements of DPGEsul are >100 times larger than previous results but smaller than anticipated based on comparison of alloy solubilities in sulfide melts and S-free silicate melts. The presence of S in the silicate melt greatly increases alloy solubility. We use our new set of partition coefficients to develop a fully constrained model of PGE behavior during melting which accurately predicts the abundances of PGE in mantle-derived magmas and their restites, including mid-ocean ridge basalts, continental picrites, and the parental magmas of the Bushveld Complex of South Africa. Our model constrains mid-ocean ridge basalt (MORB) to be the products of pooled low and high degree fractional melts. Within-plate picrites are pooled products of larger degrees of fractional melting in columnar melting regimes. A significant control on PGE fractionation in mantle-derived magmas is exerted by residual alloy or platinum group minerals in their source. At low pressures (e.g., MORB genesis) the mantle residual to partial melting retains primitive mantle inter-element ratios and abundances of PGE until sulfide has been completely dissolved but then evolves to extremely high Pt/Pd and low Pd/Ir because Pt and Ir alloys form in the restite. During melting at high pressure to form picrites or komatiites Ir alloy appears as a restite phase but Pt alloy is not stable due to the large effect of pressure on fS2, and of temperature on fO2 along an internal oxygen buffer, which causes large increases in alloy solubility. The magmas parental to the Bushveld Complex of South Africa appear, at least in part, to be partial melts of mantle that has previously been melted to the point of total sulfide exhaustion at low pressure, closely resembling mantle xenoliths of the Kaapvaal craton. Using the new extremely large DPGEsul the world-class Merensky Reef and UG2 Pt deposits of the Bushveld Complex can readily be modeled as the result of sulfide saturation due to mixing of magmas with unremarkable PGE contents, obviating the need to postulate anomalously PGE-rich parent magmas or hydrothermal inputs to the deposits.

Mungall, James E.; Brenan, James M.

2014-01-01

257

Determination of Earth structure using waveform inversion and Spectral-Element Method  

NASA Astrophysics Data System (ADS)

Recent progress in large scale computing by using Spectral-Element Method and the Earth Simulator has demonstrated possibilities to perform full-waveform inversion of three dimensional (3D) seismic velocity structure inside the Earth. Specifically Liu and Tromp (2006) have shown that it becomes feasible to compute finite frequency kernel for seismic velocity structure based on adjoint method. We plan to apply their method to obtain 3D velocity structure beneath East Asia. We take one chunk from global mesh of Spectral-Element Method and compute synthetic seismograms with accuracy of about 10 second. We use GAP-P2 mantle tomography model (Obayashi et al., 2009) as an initial 3D model and try to use as many broadband seismic stations available in this region, including Ocean Bottom Seismographs deployed in Philippine sea, as possible to perform inversion. Before accumulating finite frequency adjoint kernels for seismic velocity structure, we estimated influences of the initial 3D model on the focal mechanism and hypocenter location. We chose earthquakes occurred at various locations and depths in this region from Global CMT catalog. We picked up time windows for P and S waves that give decent match between data and synthetics for 3D model and determine the best fit solutions for source mechanism and hypocenter. We found that the redetermined solutions do not differ much from the Global CMT solutions, which shows that he Global CMT solutions can be used as initial solutions in the inversion. We then use the time windows for P and S waves to compute adjoint sources and calculate adjoint kernels for seismic velocity structure. We will discuss source and receiver pairs obtained in this region for the inversion and the sensitivities of the kernels to specific structure inside Earth.

Obayashi, M.; Tsuboi, S.; Tono, Y.; Suetsugu, D.

2010-12-01

258

Computational Design of Solar Energy Harvesting Materials Made of Earth-Abundant Elements  

NASA Astrophysics Data System (ADS)

Very large-scale deployment of photovoltaic (PV) technology based on both the first and second generation solar cells posts serious questions on the materials supply as they rely on either high-purity and high-quality silicon crystals or rare elements such as indium and tellurium. ``Ancient'' PV materials made of earth-abundant elements, such as oxides and sulfides of copper and iron, have attracted resurgent interests. There is also intensive research devoted to the search for ``modern'' earth-abundant PV materials, with a recent promising example being Cu2ZnSnSe4. Computational approaches play a key role in this endeavor by guiding the screening and optimization of the materials toward high device performance. In this paper, I will focus on two aspects of computational design of earth-abundant PV materials. First, I will discuss the methods for accurately predicting band gaps of semiconductor materials. The emphasis will be on the performance of hybrid functional method on different classes of materials. Based on these understandings, I will discuss how to tune the band gap of a material to match the solar spectrum. For example, one could reduce of the band gap of anatase to 1.5 eV by the chemical codoping approach. Second, I will discuss the methods for accurate computation of defect properties, which is important as the defectiveness is intrinsic to the low-cost synthesized materials. I will introduce a method for calculation of defect formation energies by minimizing the error due to the ``band-gap problem'' of the density functional theory. I will also discuss approaches to mitigating the effects of defects, e.g., by passivation.

Sun, Yiyang

2012-02-01

259

Just How Earth-like are Extrasolar Super-Earths? Constraints on H+He Envelope Fractions from Kepler's Planet Candidates  

NASA Astrophysics Data System (ADS)

With 3500 planetary candidates discovered in its first 3 years of data, the Kepler Mission promises to answer one of the most fundamental questions posed in exoplanetary research: what kinds of planets occur most often in our Galaxy? As Kepler primarily yields planetary radii and orbital periods, it has enabled numerous studies of the occurrence rate of planets as a function of these variables. Unfortunately, the full mass distribution, and thus a direct measure of these planets' possible compositions, remains elusive due to the unsuitability of these faint targets for radial velocity follow-up and the relative rareness of transit timing variations. We show, however, that relatively straightforward models of planetary evolution in an irradiated environment can make some progress without this full mass distribution towards understanding bulk compositions of the abundant Super-Earth/Sub-Neptunes that Kepler has discovered. In particular, we constrain the distribution of envelope fractions, i.e. the fraction of a planet's mass that is in a gaseous hydrogen and helium envelope around its rocky core, for this exoplanet population that has no analogs in our Solar System.

Wolfgang, Angie; Lopez, E.; Kepler Team; SAMSI Bayesian Characterization of Exoplanet Populations Working Group

2013-10-01

260

Size fractionation of wood extractives, lignin and trace elements in pulp and paper mill wastewater before and after biological treatment.  

PubMed

Integrated kraft pulp and paper mill wastewater was characterized before (influent) and after (effluent) the activated sludge process by microfiltration (8, 3, 0.45 and 0.22 microm) and ultrafiltration (100, 50, 30 and 3 kDa) into different size fractions. Wood extractives, lignin, suspended solids and certain trace elements were determined in each fraction. Forty four percent of the resin and fatty acids in the influent (12.8 mg/L) occurred in particles (>0.45 microm), 20% as colloids (0.45 microm-3 kDa) and 36% in the <3 kDa fraction. The corresponding values for sterols (1.5 mg/L) were 5, 46 and 49%. In the effluent, resin and fatty acids (1.45 mg/L) and sterols (0.26 mg/L) were mainly present in the <3 kDa fraction, as well as a small proportion in particles. beta-sitosterol was present in particles in the effluent (88+/-50 microg/L). Lignin in the influent was mainly in the colloidal and <3 kDa fractions, whereas in the effluent it was mainly in the <3 kDa fraction. Thus the decrease of lignin in the biological treatment was concentrated on the colloidal fraction. In the influent, Mn, Zn and Si were mainly present in the <3 kDa fraction, whereas a significant proportion of Fe and Al were found also in the particle and colloidal fractions. In the effluent, Fe and Al were mainly present in the colloidal fraction; in contrast, Mn, Zn and Si were mainly in the <3 kDa fraction. The results indicated that the release of certain compounds and elements into the environment could be significantly decreased or even prevented simply by employing microfiltration as a final treatment step or by enhancing particle removal in the secondary clarifier. PMID:19524281

Leiviskä, Tiina; Rämö, Jaakko; Nurmesniemi, Hannu; Pöykiö, Risto; Kuokkanen, Toivo

2009-07-01

261

Thermodynamic properties of the rare earth element vapor complexes LnAl{sub 3}Cl{sub 12} from Ln = La to Ln = Lu  

SciTech Connect

The rare earth element complexes have never been analyzed in the gaseous state due to experimental concerns. The thermodynamic properties of rare earth element complexes are important for various applications, from high-intensity discharge lamps to recovery of rare earth metals. 46 refs., 4 figs., 1 tab.

Zhi-Chang Wang; Lin-Shan Wang [Northeastern Univ., Liaoning (China)

1997-04-09

262

High Temperature Iron Isotopic Fractionation in Earths Mantle - An Experimental Approach  

Microsoft Academic Search

A recent study (Williams et al. 2004) presented iron isotope data for a suite of mantle minerals in an attempt to determine whether iron isotopic fractionation could be used as a tracer for changes in mantle oxidation state. These workers found lower 57Fe\\/^{54}Fe for mantle spinels with higher oxygen fugacity and an inverse correlation between 57Fe\\/^{54}Fe and Fe3+ concentration in

A. Shahar; C. E. Manning; E. D. Young

2006-01-01

263

Speciation of rare earth elements in soil by sequential extraction then HPLC coupled with visible and ICP-MS detection.  

PubMed

The distribution of rare earth elements (REE) in a pooled soil sample collected from Zhangzhou, Fujian Province, China, was screened by a five-step sequential extraction procedure coupled with ICP-MS determination after preconcentration of REE and removal of the matrix by extraction with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP). The results showed that the distribution of REE in the different fractions of the pooled soil sample studied followed the order soluble species (46.76%) > species bound to organic matter (22.08%) > species in the residue (16.77%) > species bound to Fe-Mn oxides (2.02%). An effective method for speciation of REE, which utilized weak cation-exchange HPLC separation hyphenated with post-column derivatization and visible or on line ICP-MS detection, was, moreover, developed and successfully applied to the speciation of REE in the soluble extract of the pooled soil sample. The stability of known complexes of lanthanum during the HPLC separation was investigated with fluoride, citrate, and ethylenediamine tetraacetic acid (EDTA) chosen as ligands modeling those in the soil. REE in the soluble extract of the pooled soil sample were subsequently classified into three types of species--< or = +1 charged complexes (negatively charged, neutral, and +1 charged), +2 charged complexes, and "free" REE species. This method is expected to be useful for identification of bioavailable (or toxic) species of REE in environmental samples. PMID:11583084

Wang, Q; Huang, B; Guan, Z; Yang, L; Li, B

2001-08-01

264

Distribution patterns of rare-earth elements and uranium in tertiary sedimentary phosphorites of Hahotoé Kpogamé, Togo  

NASA Astrophysics Data System (ADS)

Seventeen samples have been used to study the distribution behaviour of rare-earth elements and uranium in four profiles of the exploited phosphatic layer C1 of Hahotoé-Kpogamé deposits in Togo. Compared with shale values (NASC: North American Shale Composite) these phosphorites are enriched with REE by factors of 4-7 and with uranium by a factor of 43. REE display seawater-like distribution patterns with a pronounced negative cerium anomaly and an enrichment of light REE relative to shales. The phosphorite deposits of Togo are altered in a tropical climate that led to the formation of crandallite, kaolinite and goethite at the expense of francolite and clay minerals. Horizons rich in crandallite, kaolinite and goethite accumulate high amounts of REE and uranium released during the weathering of phosphorites. The alteration does not considerably affect the Ce-anomalies which remain negative for all samples but does affect the REE fractionation whereby crandallite, kaolinite and goethite rich samples show an enrichment of heavy REE compared with the light ones.

Gnandi, Kissao; Tobschall, Heinz J.

2003-08-01

265

Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa  

NASA Astrophysics Data System (ADS)

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The 87Sr/ 86Sr ratios of the chimneys indicate that they have precipitated from a mixture of lake water (more than 95%) and hydrothermal fluids. No zoning in the chimneys was detected with our Sr data. For the rare-earth elements, the situation is more complex. The external walls of the chimneys are rare-earth-element-poor (La ? 500 ppb, Yb ? 200 ppb, La/Yb = 2 to 3.4). Their shale normalised rare-earth element patterns suggest that they are in equilibrium with the inferred carbonate-depositing fluids. The rare-earth element concentrations of the internal walls of the chimneys are significantly light rare earth elements (LREE)-enriched with La contents sometimes up to 5 ppm. We suggest that they contain more vent-fluid rare-earth elements than the external wall samples, possibly adsorbed on the surface of growing crystals or simply hosted by impurities. It was not possible to constrain the nature of these phases, but the variations of the compositions of the internal wall materials of the active chimneys with time, as well as data obtained on an inactive chimney indicate that this rare-earth element excess is mobile. Partition coefficients were calculated between the external wall aragonite and carbonate-depositing fluid. The results are strikingly similar to the values obtained by Sholkovitz and Shen (1995) on coral aragonite, and suggest that there is no significant biologic effect on the incorporation of rare-earth elements into coral aragonite and that the various carbonate complexes involved Me(CO 3+) complexes are the main LREE carriers in seawater (Cantrell and Byrne, 1987) instead of Me(CO 3) 2- in Banza fluids) have the same behaviour during aragonite precipitation.

Barrat, J. A.; Boulègue, J.; Tiercelin, J. J.; Lesourd, M.

2000-01-01

266

Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa  

SciTech Connect

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The {sup 87}Sr/{sup 86}Sr ratios of the chimneys indicate that they have precipitated from a mixture of lake water (more than 95%) and hydrothermal fluids. No zoning in the chimneys was detected with the Sr data. For the rare-earth elements, the situation is more complex. The external walls of the chimneys are rare-earth-element-poor (La {approx} 500 ppb, Yb {approx} 200 ppb, La/Yb = 2 to 3.4). Their shale normalized rare-earth element patterns suggest that they are in equilibrium with the inferred carbonate-depositing fluids. The rare-earth element concentrations of the internal walls of the chimneys are significantly light rare earth elements (LREE)-enriched with La contents sometimes up to 5 ppm. The authors suggest that they contain more vent-fluid rare-earth elements than the external wall samples, possibly adsorbed on the surface of growing crystals or simply hosted by impurities. It was not possible to constrain the nature of these phases, but the variations of the compositions of the internal wall materials of the active chimneys with time, as well as data obtained on an inactive chimney indicate that this rare-earth element excess is mobile. Partition coefficients were calculated between the external wall aragonite and carbonate-depositing fluid. The results are strikingly similar to the values obtained by Sholkovitz and Shen (1995) on coral aragonite, and suggest that there is no significant biologic effect on the incorporation of rare-earth elements into coral aragonite and that the various carbonate complexes involved Me(CO{sub 3}{sup +}) complexes are the main LREE carriers in seawater instead of Me(CO{sub 3}){sub 2}{sup {minus}} in Banza fluids have the same behavior during aragonite precipitation.

Barrat, J.A.; Boulegue, J.; Tiercelin, J.J.; Lesourd, M.

2000-01-01

267

Identifying calcium sources at an acid deposition-impacted spruce forest: A strontium isotope, alkaline earth element multi-tracer approach  

USGS Publications Warehouse

Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured 87Sr/86Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87Sr/86Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87Sr/86Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible alternative explanations of aspects of the observed trends, the chemical buffering capacity of the forest floor-biomass pool limits their effectiveness as causal mechanisms. ?? Springer 2005.

Bullen, T. D.; Bailey, S. W.

2005-01-01

268

'Nano' Morphology and Element Signatures of Early Life on Earth: A New Tool for Assessing Biogenicity  

NASA Technical Reports Server (NTRS)

The relatively young technology of NanoSIMS is unlocking an exciting new level of information from organic matter in ancient sediments. We are using this technique to characterize Proterozoic organic material that is clearly biogenic as a guide for interpreting controversial organic structures in either terrestrial or extraterrestrial samples. NanoSIMS is secondary ion mass spectrometry for trace element and isotope analysis at sub-micron resolution. In 2005, Robert et al. [1] combined NanoSIMS element maps with optical microscopic imagery in an effort to develop a new method for assessing biogenicity of Precambrian structures. The ability of NanoSIMS to map simultaneously the distribution of organic elements with a 50 nm spatial resolution provides new biologic markers that could help define the timing of life s development on Earth. The current study corroborates the work of Robert et al. and builds on their study by using NanoSIMS to map C, N (as CN), S, Si and O of both excellently preserved microfossils and less well preserved, non-descript organics in Proterozoic chert from the ca. 0.8 Ga Bitter Springs Formation of Australia.

Oehler, D. Z.; Mostefaoui, S.; Meibom, A.; Selo, M.; McKay, D. S.; Robert, F.

2006-01-01

269

Distribution of trace elements in filtered and non filtered aqueous fractions: Insights from rivers and streams of Sardinia (Italy)  

Microsoft Academic Search

The distribution of several trace elements in different aqueous fractions has been studied in running waters from Sardinia (Italy). Trace elements and major components were determined in water samples collected at high- and low-discharge from rivers (90 samples) and streams (70 samples). At selected sites, total (non filtered samples) and dissolved (0.4?m and 0.015?m pore-size filtered samples) amounts of trace

Rosa Cidu; Franco Frau

2009-01-01

270

Earth  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on our plant Earth. There is a section about water on earth and its many different varities, like freshwater, groundwater, and frozen water. There is information about the chemical make-up of water and many images showing the different water anvironments. There is a section about life in water, such as animals, plants, and plankton.

2008-10-03

271

Characterizing ablation and aerosol generation during elemental fractionation on absorption modified lithium tetraborate glasses using LA-ICP-MS.  

PubMed

The influence of sample matrix composition, absorption behavior and laser aerosol particle size distribution on elemental fractionation in laser ablation inductively coupled plasma mass spectrometry was studied for nanosecond laser ablation at a wavelength of 266 nm. To this end, lithium tetraborate glass samples with different iron oxide contents and trace amounts of a group of 11 elements were prepared synthetically. The samples were characterized in terms of optical absorbance, melting points, trace element concentrations and homogeneity. UV/VIS spectra showed that sample absorption rises with increasing Fe2O3 content. Crater depths and time-dependent particle size distributions were measured, and ablated and transported sample volumes were estimated. Furthermore, the laser aerosol was filtered using a particle separation device and transient ICP-MS signals were acquired with and without filtering the aerosol. The results demonstrate that the amount of ablated sample is related to the absorption coefficient of the sample and therefore to the optical penetration depth of the laser beam into the sample. The higher energy densities resulting from the shorter penetration depths result in smaller average particle sizes for highly absorbing samples, which allows more efficient transport to and atomization and excitation of the ablated material within the ICP. The particle size distribution changes continuously with ablation time, and larger particle fractions occur mainly at the beginning of the ablation, which leads to particle-related fractionation processes at the beginning of the transient signal. Exceeding a critical depth to diameter ratio, laser-related elemental fractionation processes occur. Changes in the volatile to non-volatile element intensity ratio after the aerosol is filtered indicate that particle size-related enrichment processes contribute to elemental fractionation. PMID:15616778

Weis, Peter; Beck, Horst P; Günther, Detlef

2005-01-01

272

Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: the importance of accessory mineral inclusions  

Microsoft Academic Search

REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare earth titano-silicate) included within clinopyroxenes from the

P MICHAEL

1988-01-01

273

Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: The importance of accessory mineral inclusions  

Microsoft Academic Search

REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare earth titano-silicate) included within clinopyroxenes from the

Peter J. Michael

1988-01-01

274

Development and application of a sensitive and rapid analytical method to determine the rare-earth elements in surface waters  

Microsoft Academic Search

A new cost-effective method to determine the 14 rare-earth elements (REE's) in waters to levels as low as 0.2–1.0 ng l?1 (ppt) has been established. Inductively coupled plasma mass spectrometry (ICP-MS) is used for measurement following automated preconcentration using the Dionex® MetPac CC-1 resin of iminodiacetate functionality. The free REE ion is chelated onto the resin while alkali and alkaline-earth

Gwendy E. M. Hall; Judy E. Vaive; John W. McConnell

1995-01-01

275

Origin of middle rare earth element enrichment in acid mine drainage-impacted areas.  

PubMed

The commonly observed enrichment of middle rare earth elements (MREE) in water sampled in acid mine drainage (AMD)-impacted areas was found to be the result of preferential release from the widespread mineral pyrite (FeS2). Three different mining-impacted sites in Europe were sampled for water, and various pyrite samples were used in batch experiments with diluted sulphuric acid simulating AMD-impacted water with high sulphate concentration and high acidity. All water samples independent on their origin from groundwater, creek water or lake water as well as on the surrounding rock types showed MREE enrichment. Also the pyrite samples showed MREE enrichment in the respective acidic leachate but not always in their total contents indicating a process-controlled release. It is discussed that most probably complexation to sulphite (SO3 (2-)) or another intermediate S-species during pyrite oxidation is the reason for the MREE enrichment in the normalized REE patterns. PMID:24385183

Grawunder, Anja; Merten, Dirk; Büchel, Georg

2014-06-01

276

Rare earths, other trace elements and iron in Luna 20 samples.  

NASA Technical Reports Server (NTRS)

The results of the analysis by neutron activation of six samples from the Luna 20 mission and one sample of less than 1 mm fines from Apollo 16 are reported. The concentrations of the rare-earth elements (REE) in the samples of fines from Luna 20 and Apollo 16 are less than those found for corresponding materials from the mare areas but a negative Eu anomaly is still present. The concentrations of the REE in fines from Luna 20 are only about two-thirds as great as in the sample of Apollo 16 fines, but the concentration of Co, Sc and Cr are greater by factors ranging from 1.5 to 2.3.

Helmke, P. A.; Blanchard, D. P.; Jacobs, J. W.; Haskin, L.; Haskin, A.

1973-01-01

277

Light shifts and magic wavelengths for heavy alkaline earth elements: Ba and Ra  

NASA Astrophysics Data System (ADS)

In this paper, we investigate light shifts of heavy alkaline earth elements barium (Ba) and radium (Ra), which are interesting for optical lattice clocks and for permanent electric dipole moment searches. Detailed knowledge is required in the design of efficient loading of atoms from a magneto-optical trap into an optical dipole trap, to facilitate Doppler cooling while trapping and to achieve longer lifetimes of the trapped atoms with reduced heating rates. The wavelength dependence of light shifts of the ns2 1S0 ground state, the nsnp 3P1 and ns(n - 1)d 1D2 excited states in barium (n = 6) and the n s2 1S0 ground state, the nsnp 3P1 and ns(n - 1)d 3D2 excited states in radium (n = 7) are calculated. Several magic wavelengths in the visible and infrared regions accessible with commercial lasers for optical dipole trapping of Ba and Ra are identified.

Dammalapati, U.; Santra, B.; Willmann, L.

2012-01-01

278

Isomorphous substitutions of rare earth elements for calcium in synthetic hydroxyapatites.  

PubMed

Polycrystalline hydroxyapatites Ca(10-x)REE(x)(PO(4))(6)(OH)(2-x)O(x) were synthesized and studied by X-ray powder diffraction, infrared absorption, diffuse-reflectance spectroscopy, and thermogravimetry. The solubility limits x(max) of rare earth elements (REE) in Ca hydroxyapatites decreases with an increasing REE atomic number from x(max) = 2.00 for La, Pr, and Nd to x(max) = 0.20 for Yb at 1100 °C. Refinements of X-ray diffraction patterns by the Rietveld method show that REE atoms substitute for Ca preferentially at the Ca(2) sites of the apatite structure. The substitution decreases the Ca(2)-O(4) atomic distances in the calcium coordination polyhedra and increases the Ca(2)-O(1,2,3) distances. This observation shows that interatomic distances depend not only on radii of the ions involved in the substitution but also on their charges. PMID:20957990

Ardanova, Lyudmyla I; Get'man, Evgeni I; Loboda, Stanislav N; Prisedsky, Vadim V; Tkachenko, Tatiana V; Marchenko, Valeriy I; Antonovich, Valeriy P; Chivireva, Nataliya A; Chebishev, Konstantin A; Lyashenko, Alexandra S

2010-11-15

279

Behavior of Rare Earth Element In Geothermal Systems; A New Exploration/Exploitation Tool  

SciTech Connect

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells have been sampled from a number of locations, including: (1) the North Island of New Zealand (1 set of samples); (2) the Cascades of Oregon; (3) the Harney, Alvord Desert and Owyhee geothermal areas of Oregon; (4) the Dixie Valley and Beowawe fields in Nevada; (5) Palinpion, the Philippines: (6) the Salton Sea and Heber geothermal fields of southern California; and (7) the Dieng field in Central Java, Indonesia. We have analyzed the samples from all fields for REE except the last two.

Scott A. Wood

2002-01-28

280

Enhancement of ferroelectricity and ferromagnetism in rare earth element doped BiFeO3  

NASA Astrophysics Data System (ADS)

Rare earth element doped BiFeO3 thin films were fabricated using the pulsed laser deposition method and various targets made from different starting Fe2O3 and Fe3O4 iron source materials. The films fabricated using the targets made from Fe3O4 exhibit great enhancement in their ferroelectricity, due to greatly reduced electrical leakage, as well as enhanced magnetization compared to those films deposited using targets from Fe2O3. It is suggested that the Fe2+ ion plays an important role in compensating for the charge imbalance and reducing current leakage, as well as enhancing the magnetic moment through the introduction of antiferrimagnetic ordering at Fe2+ site.

Cheng, Z. X.; Wang, X. L.; Dou, S. X.; Kimura, H.; Ozawa, K.

2008-12-01

281

Effects of continents on Earth cooling: Thermal blanketing and depletion in radioactive elements  

NASA Astrophysics Data System (ADS)

Estimate of mantle heat flow under continental shields are very low, indicating a strong insulating effect of continents on mantle heat loss. This effect is investigated with a simple approach: continents are introduced in an Earth cooling model as perfect thermal insulators. Continental growth rate has then a strong influence on mantle cooling. Various continental growth models are tested and are used to compute the mantle depletion in radioactive elements as a function of continental crust extraction. Results show that the thermal blanketing effect of continents strongly affects mantle cooling, and that mantle depletion must be taken into account in order not to overestimate mantle heat loss. In order to obtain correct oceanic heat flow for present time, continental growth must begin at least 3 Gy ago and steady-state for continental area must be reached for at least 1.5 Gy in our cooling model.

Grigné, Cécile; Labrosse, Stéphane

282

Galileo Earth approach navigation using connected-element interferometer phase-delay tracking  

NASA Technical Reports Server (NTRS)

The application of a Connected-Element Interferometer (CEI) to the navigation of the Galileo spacecraft during its encounter with Earth in December 1990 is investigated. A CEI tracking demonstration is planned for the week of November 11 through 18, 1990, from 27 days to 20 days prior to Earth encounter on December 8. During this period, the spacecraft will be tracked daily with Deep Space Network Stations 13 and 15 at Goldstone. The purpose of this work is twofold: first, to establish and define the navigation performance expected during the tracking demonstration and, second, to study, in a more general sense, the sensitivity of orbit demonstration results obtained with CEI to the data density within CEI tracking passes and to important system parameters, such as baseline orientation errors and the phase-delay measurement accuracy. Computer simulation results indicate that the use of CEI data, coupled with conventional range and Doppler data, may reduce the uncertainty in the declination of the spacecraft's incoming trajectory by 15 to 66 percent compared with the operational solution using range and Doppler data only. The level of improvement depends upon the quantity and quality of the CEI data.

Thurman, S. W.

1990-01-01

283

Rare earth elements in human hair from a mining area of China.  

PubMed

Rare earth minerals have been mined for more than 50 years in Inner Mongolia of China. In the mining area rare earth elements (REE) may be significantly accumulated in humans. Therefore, the aim of this paper is to characterize the REE concentrations in hair of local residents. REE concentrations in hair of 118 subjects were determined. The results showed that the mean concentrations of the determined REE in the hair of both females and males were usually higher from mining area than from control area. The mean concentrations of all the fifteen REE were much higher in hair of males than in hair of females from mining area. This suggested that males might be more sensitive to REE than females. In addition, the mean contents of the REE in hair of miners, particularly light REE (La, Ce, Pr and Nd), were usually much higher than the values in hair of non-miners from both mining area and control area, indicating that the miners were exposed to higher concentrations of REE in occupational environment. Among age groups, the relationships between REE concentrations and age groups showed that more and more concentrations of light REE accumulated in body of both females and males with age until 60 years, while heavy REE concentrations decreased with age in males who were exposed to low concentrations of heavy REE. PMID:23830573

Wei, Binggan; Li, Yonghua; Li, Hairong; Yu, Jiangping; Ye, Bixiong; Liang, Tao

2013-10-01

284

Quantitative estimation of concentrations of dissolved rare earth elements using reflectance spectroscopy  

NASA Astrophysics Data System (ADS)

Characteristic spectral parameters such as the wavelength and depth of absorption bands are widely used to quantitatively estimate the composition of samples from hyperspectral reflectance data in soil science, mineralogy as well as vegetation study. However, little research has been conducted on the spectral characteristic of rare earth elements (REE) and their relationship with chemical composition of aqueous solutions. Reflectance spectra of ore leachate solutions and contaminated stream water from a few REE mines in the Jiangxi Province, China, are studied for the first time in this work. The results demonstrate that the six diagnostic absorption features of the rare earths are recognized in visible and near-infrared wavelengths at 574, 790, 736, 520, 861, and 443 nm. The intensity of each of these six absorption bands is linearly correlated with the abundance of total REE, with the r2 value >0.95 and the detection limit at ?75,000 ?g/L. It is suggested that reflectance spectroscopy provides an ideal routine analytical tool for characterizing leachate samples. The outcome of this study also has implications for monitoring the environmental effect of REE mining, in particular in stream water systems by hyperspectral remote sensing.

Dai, Jingjing; Wang, Denghong; Wang, Runsheng; Chen, Zhenghui

2013-01-01

285

Rare earth element complexation by PO 43- ions in aqueous solution  

NASA Astrophysics Data System (ADS)

Complexation of trivalent rare earths by PO 43- ions has been assessed at t = 25° C by examining the influence of aqueous phosphate concentrations on the distributions of 144Ce and 153Gd between 0.68 molar NaClO 4 and tributyl phosphate (TBP). Estimated Ce 3+ and Gd 3+ phosphate complexation constants appropriate to zero ionic strength are Ce3+ + PO43- ? CePO40; logL?10 ? 11.7 Gd3+ + PO43- ? GdPO40; logL?1o = 12.2. Our estimates of these formation constants at zero ionic strength are approximately seven to eight orders of magnitude lower than previously reported estimates for lanthanide and actinide PO 43- complexation. Linear free energy relationships relating the complexation of Ca 2+ and lanthanides (Ln 3+) by a variety of organic ligands, in conjunction with previous direct observations of CaPO 4- formation, are consistent with the experimentally derived CePO 40 and GdPO 40 formation constants reported in this work. Gadolinium speciation calculations indicate that the PO 43- ion can effectively compete with the CO 32- ion for free Gd 3+ in model groundwater at pH 7-9. Rare earth element phosphate complexation is a significant process in natural freshwater systems which are neutral to mildly basic when the concentration ratio [HPO 42-] /[HCO 3-] is greater than approximately 1 × 10 -3.

Byrne, Robert H.; Lee, Jong Hyeon; Bingler, Linda S.

1991-10-01

286

Determination of Earth structure using waveform inversion and Spectral-Element Method for Eastern Asian region  

NASA Astrophysics Data System (ADS)

Recent progress in large scale computing by using Spectral-Element Method and the Earth Simulator has demonstrated possibilities to perform full-waveform inversion of three dimensional (3D) seismic velocity structure inside the Earth. Specifically Liu and Tromp (2006) have shown that it becomes feasible to compute finite frequency kernel for seismic velocity structure based on adjoint method. We apply their method to obtain 3D velocity structure beneath East Asia. We take one chunk from global mesh of Spectral-Element Method and compute synthetic seismograms with accuracy of about 10 second. We use GAP-P2 mantle tomography model (Obayashi et al., 2009) as an initial 3D model and try to use as many broadband seismic stations available in this region, including Ocean Bottom Seismographs deployed in Philippine sea, as possible to perform inversion. We calculate synthetic seismograms for this initial 3D model and source receiver pairs. We then use the time windows for P and S waves to compute adjoint sources and calculate misfit adjoint kernels for seismic velocity structure. The kernels are calculated for all the time windows of P and S waves simultaneously. We sum up the event misfit kernels and perform the first iteration to improve the initial velocity model using the steepest decent method. The results of the first iteration shows that the differences between the initial model and the improved model is less than 1%, which shows that the modification resulted from the first iteration was quite modest. However the modifications to the initial model show different pattern among P-waves and S-waves, which implies that the scaling relation to obtain S-waves velocity model from P-wave velocity model might be revised in this region.

Tsuboi, S.; Obayashi, M.; Tono, Y.; Suetsugu, D.

2011-12-01

287

A major light rare-earth element (LREE) resource in the Khanneshin carbonatite complex, southern Afghanistan  

USGS Publications Warehouse

The rapid rise in world demand for the rare-earth elements (REEs) has expanded the search for new REE resources. We document two types of light rare-earth element (LREE)-enriched rocks in the Khanneshin carbonatite complex of southern Afghanistan: type 1 concordant seams of khanneshite-(Ce), synchysite-(Ce), and parisite-(Ce) within banded barite-strontianite alvikite, and type 2 igneous dikes of coarse-grained carbonatite, enriched in fluorine or phosphorus, containing idiomorphic crystals of khanneshite-(Ce) or carbocernaite. Type 1 mineralized barite-strontianite alvikite averages 22.25 wt % BaO, 4.27 wt % SrO, and 3.25 wt % ? LREE2O3 (sum of La, Ce, Pr, and Nd oxides). Type 2 igneous dikes average 14.51 wt % BaO, 5.96 wt % SrO, and 3.77 wt % ? LREE2O3. A magmatic origin is clearly indicated for the type 2 LREE-enriched dikes, and type 1 LREE mineralization probably formed in the presence of LREE-rich hydrothermal fluid. Both types of LREE mineralization may be penecontemporaneous, having formed in a carbonate-rich magma in the marginal zone of the central vent, highly charged with volatile constituents (i.e., CO2, F, P2O5), and strongly enriched in Ba, Sr, and the LREE. Based on several assumptions, and employing simple geometry for the zone of LREE enrichment, we estimate that at least 1.29 Mt (million metric tonnes) of LREE2O3 is present in this part of the Khanneshin carbonatite complex.

Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Horton, Forrest; Buttleman, Kim; Scott, Emily R.

2012-01-01

288

Natural radioactivity and rare earth elements in feldspar samples, Central Eastern desert, Egypt.  

PubMed

The pegmatite bodies of the Eastern Desert of Egypt are widely distributed especially along the Marsa-Alam-Idfu road. The Abu Dob area covers about 150km(2) of the Arabian Nubian shield at the central part of the Eastern Desert of Egypt. Most of the pegmatite is zoned; the zonation starts with milky quartz at the core followed by alkali feldspar at the margins. The feldspars vary in color from rose to milky and in composition from K-feldspar to Na-feldspar, sometimes interactions of both types are encountered. Thirteen feldspar samples were collected from different locations in the Abu Dob area for measuring the natural radioactivity of (238)U, (232)Th and (40)K using an HPGe detector. The variation in concentration of radionuclides for the area under investigation can be classified into regions of high, medium and low natural radioactivity. The average concentration in BqKg(-1) has been observed to be from 9.5 to 183675.7BqKg(-1) for (238)U, between 6.1 and 94,314.2BqKg(-1) for (232)Th and from 0 to 7894.6BqKg(-1) for (40)K. Radium equivalent activities (Ra(eq)), dose rate (D(R)) and external hazard (H(ex)) have also been determined. In the present work, the concentration of rare earth elements are measured for two feldspar samples using two techniques, Environmental Scanning Electron microscope XIL 30 ESEM, Philips, and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The existence of rare earth elements in this area are very high and can be used in different important industries. PMID:21324705

Walley El-Dine, Nadia; El-Shershaby, Amal; Afifi, Sofia; Sroor, Amany; Samir, Eman

2011-05-01

289

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

SciTech Connect

Ion probe measurements of the rare earth element (REE) concentrations of individual grains of the Shergotty meteorite are reported. Phases analyzed include whitlockite, apatite, baddeleyite, augite, pigeonite, maskelynite and K-rich glass. U concentrations of whitlockite and apatite crystals were also obtained. The whole rock REE pattern is dominated by whitlockite, which contains over 95% of the light rare earth elements (LREE). REE concentrations in apatite are much lower than estimated by Laul et al. (1986). All of the whitlockites have the same relative abundances of LREE. The observation, by Jones et al. (1985), of a skeletal whitlockite with LREE enrichment is not confirmed by analyses of the same grain. Pyroxene rims are not enriched in LREE. No leachable carrier, enriched in LREE and associated with pyroxene, has been found. Instead, either a laboratory contamination or a petrographically cryptic phase such as a film on grain boundaries is suspected as the carrier of LREE enrichments. Estimates of REE abundances in the Shergotty intercumulus melt indicate that a complex petrogenesis is required, in agreement with the conclusions of McKay et al. (1986a). Pyroxene distribution coefficients measured experimentally are compared with estimates from measured REE abundances in augite and pigeonite. Evolution of REE abundances in the Shergotty late-stage interstitial melt, as inferred from analyses of whitlockite, conforms with trends predicted from partitioning considerations, and requires no special processes such as metasomatism. The average U concentrations of whitlockite and apatite are respectively 540 and 1,550 ppb. Although the calcium phosphates are enriched in U, they contain less than 20% of the U in Shergotty.

Lundberg, L.L.; Crozaz, G.; Zinner, E. (Washington Univ., St. Louis, MO (USA)); McKay, G. (NASA, Johnson Space Center, Houston, TX (USA))

1988-08-01

290

Rare earth elements in Holocene reefal microbialites: a new shallow seawater proxy  

NASA Astrophysics Data System (ADS)

The concentration of rare earth elements and yttrium (REE + Y) was determined in Holocene Mg-calcite microbialites from shallow reef framework cavities at Heron Reef, Great Barrier Reef. Shale-normalized REE + Y patterns of 52 microbialite samples show: (1) uniform heavy REE enrichment (Nd SN/Yb SN = 0.236, SD = 0.026); (2) consistent negative Ce and positive La anomalies; (3) marine Y/Ho ratios (56.17, SD = 2.66); and (4) slightly positive Gd anomalies. All of these features are consistent with the geochemistry of well-oxygenated, shallow ambient seawater. REE partition coefficients were calculated relative to shallow Coral Sea seawater. They are uniform (relative SD = 10.2%) across the entire mass range and almost two orders of magnitude higher than those between coral and seawater. Hence, terrigenous detritus-free, modern microbialites are a more reliable proxy for seawater REE chemistry than are skeletal carbonates. Ancient limestones have been considered largely problematic as sources for REE proxies owing to perceived problems with diagenesis, partly on the basis of relatively high REE concentrations in some limestones compared to modern skeletal carbonates. However, high REE concentrations in modern microbialites suggest that ancient limestones with relatively high REE concentrations, if not contaminated by terrigenous detritus, may reflect original seawater chemistry. Terrigenous contamination, if present, is readily detectable on the basis of co-occurring trace element concentrations (Sc, Hf, Th) and Y/Ho ratio. Hence, ancient, particularly reefal, limestones may provide reliable seawater REE proxies. The occurrence of microbialites in clean limestones as old as 3.5 Ga suggests the possibility of reconstructing shallow marine REE chemistry over most of Earth history with important implications for paleogeography and paleoredox studies.

Webb, Gregory E.; Kamber, Balz S.

2000-05-01

291

X-ray fluorescence analysis of rare earth elements in rocks using low dilution glass beads.  

PubMed

Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan. PMID:16038502

Nakayama, Kenichi; Nakamura, Toshihiro

2005-07-01

292

Variation in trace element content of magnetite crystallized from a fractionating sulfide liquid, Sudbury, Canada: Implications for provenance discrimination  

NASA Astrophysics Data System (ADS)

Laser ablation ICP-MS analysis has been applied to many accessory minerals in order to understand better the process by which the rock formed and for provenance discrimination. We have determined trace element concentrations of Fe-oxides in massive sulfides that form Ni-Cu-PGE deposits at the base of the Sudbury Igneous Complex in Canada. The samples represent the crystallization products of fractionating sulfide liquids and consist of early-forming Fe-rich monosulfide solution (MSS) cumulates and residual Cu-rich intermediate solid solution (ISS). This study shows that Fe-oxide geochemistry is a sensitive petrogenetic indicator for the degree of fractionation of the sulfide liquid and provides an insight into the partitioning of elements between sulfide and Fe-oxide phases. In addition, it is useful in determining the provenance of detrital Fe-oxide. In a sulfide melt, all lithophile elements (Cr, Ti, V, Al, Mn, Sc, Nb, Ga, Ge, Ta, Hf, W and Zr) are compatible into Fe-oxide. The concentrations of these elements are highest in the early-forming Fe-oxide (titanomagnetite) which crystallized with Fe-rich MSS. Upon the continual crystallization of Fe-oxide from the sulfide liquid, the lithophile elements gradually decrease so that late-forming Fe-oxide (magnetite), which crystallized from the residual Cu-rich liquid, is depleted in these elements. This behavior is in contrast with Fe-oxides that crystallized from a fractionating silicate melt, whereby the concentration of incompatible elements, such as Ti, increases rather than decreases. The behavior of the chalcophile elements in magnetite is largely controlled by the crystallization of the sulfide minerals with only Ni, Co, Zn, Mo, Sn and Pb present above detection limit in magnetite. Nickel, Mo and Co are compatible in Fe-rich MSS and thus the co-crystallizing Fe-oxide is depleted in these elements. In contrast, magnetite that crystallized later from the fractionated liquid with Cu-rich ISS is enriched in Ni, Mo and Co because Fe-rich MSS is absent. The concentrations of Sn and Pb, which are incompatible with Fe-rich MSS, are highest in magnetite that formed from the fractionated Cu-rich liquid. At subsolidus temperatures, ilmenite exsolved from titanomagnetite whereas Al-spinel exsolved from the cores of some magnetite, locally redistributing the trace elements. However, during laser ablation ICP-MS analysis of these Fe-oxides both the magnetite and its exsolution products are ablated so that the analysis represents the original magmatic composition of the Fe-oxide that crystallized from the sulfide melt.

Dare, Sarah A. S.; Barnes, Sarah-Jane; Beaudoin, Georges

2012-07-01

293

Structural Elements in a Persistent Identifier Infrastructure and Resulting Benefits for the Earth Science Community  

NASA Astrophysics Data System (ADS)

We propose a wide adoption of structural elements (typed links, collections, trees) in the Handle System to improve identification and access of scientific data, metadata and software as well as traceability of data provenance. Typed links target the issue of data provenance as a means to assess the quality of scientific data. Data provenance is seen here as a directed acyclic graph with nodes representing data and vertices representing derivative operations (Moreau 2010). Landing pages can allow a human user to explore the provenance graph back to the primary unprocessed data, thereby also giving credit to the original data producer. As in Earth System Modeling no single infrastructure with complete data lifecycle coverage exists, we propose to split the problem domain in two parts. Project-specific infrastructures such as the German project C3-Grid or the Earth System Grid Federation (ESGF) for CMIP5 data are aware of data and data operations (Toussaint et al. 2012) and can thus detect and accumulate single nodes and vertices in the provenance graph, assigning Handles to data, metadata and software. With a common schema for typed links, the provenance graph is established as downstream infrastructures refer incoming Handles. Data in this context is for example hierarchically structured Earth System model output data, which receives DataCite DOIs only for the most coarse-granular elements. Using Handle tree structures, the lower levels of the hierarchy can also receive Handles, allowing authors to more precisely identify the data they used (Lawrence et al. 2011). We can e.g. define a DOI for just the 2m-temperature variable of CMIP5 data across many CMIP5 experiments or a DOI for model and observational data coming from different sources. The structural elements should be implemented through Handle values at the Handle infrastructure level for two reasons. Handle values are more durable than downstream websites or databases, and thus the provenance chain does not break if individual links become unavailable. Secondly, a single service cannot interpret links if downstream solutions differ in their implementation schemas. Emerging efforts driven by the European Persistent Identifier Consortium (EPIC) aim to establish a default mechanism for structural elements at the Handle level. We motivate to make applications, which take part in the data lifecycle, aware of data derivation provenance and let them provide additional elements to the provenance graph. Since they are also Handles, DataCite DOIs can act as a corner stone and provide an entry point to discover the provenance graph. References B. Lawrence, C. Jones, B. Matthews, S. Pepler, and S. Callaghan, "Citation and peer review of data: Moving towards formal data publication," Int. J. of Digital Curation, vol. 6, no. 2, 2011. L. Moreau, "The foundations for provenance on the web," Foundations and Trends® in Web Science, vol. 2, no. 2-3, pp. 99-241, 2010. F. Toussaint, T. Weigel, H. Thiemann, H. Höck, M. Stockhause: "Application Examples for Handle System Usage", submitted to AGU 2012 session IN009.

Weigel, T.; Toussaiant, F.; Stockhause, M.; Höck, H.; Kindermann, S.; Lautenschlager, M.; Ludwig, T.

2012-12-01

294

Key Factors Controlling Space- and Time-Linked Rare Earth Element Distribution in Shallow Groundwaters  

NASA Astrophysics Data System (ADS)

This study investigates the effects of source-rock composition, redox changes and organic matter on the hydrochemistry of Rare Earth Elements (REE). Wetland groundwater samples as well as upland zone water samples were recovered weekly over a six month period (January to June 1999) from a small catchment (Petit Hermitage, France). The samples were filtered on the field using membrane filters of 0.22 ? m pore size, and then analyzed for their Dissolved Organic Carbon (DOC) as well as Fe, Mn, Al, Th, U and REE concentrations. The results are discussed in conjunction with previous published DOC and trace-element concentrations obtained on comparable samples from three other small catchments, namely : the Nsimi-Zoetele, Goyoum (both in Cameroon) and Kervidy/Coet-Dan (France) catchments (Viers et al., 1997; Braun et al., 1998; Dia et al., 2000). Despite marked differences (such as bioclimatic conditions, vegetation cover, basement rock composition or human activity), results are surprisingly similar with always the occurrence of two spatially distinct groundwater types including : (i) a shallow, organic-rich groundwater below wetlands recording high and variable REE contents and displaying slight or no negative Ce anomaly. In the wetland groundwaters, the REE and other trace-element concentrations seem to be controlled by seasonal dynamics, involving both temperature, whose onset at spring leads to higher organic carbon decomposition rates by microbial mass, and redox changes resulting in REE and other-trace element release in water when mineral phases occur to dissolve. (ii) The second groundwater type corresponds to a shallow, organic-poor groundwater type located below the hillslope domains. This second groundwater type displays lower REE (and other trace-element) concentrations, but distinguish from the former by the occurrence of very strong negative Ce anomalies, whose amplitude is variable, but appears to be linked to the sampling location along the catena. The comparison of the different catchments shows that the spatial variability of the REE signatures between the hillslope DOC-poor groundwaters and the wetland DOC-rich groundwaters has to be the same whatever may be the climatic and geologic context. These results assess the key roles played in the REE transfer to hydrosystems by (i) the occurrence of organic compounds, acting as a trace-element carrier phase and (ii) redox condition changes. Finally, we propose that topography could be the ultimate key factor, through its ability to control the water table depth and therefore the organic colloids enrichment when groundwaters are flowing into organic-rich soil horizons.

Dia, A.; Gruau, G.; Olivie-Lauquet, G.; Henin, O.; Petitjean, P.; Le Coz-Bouhnik, M.

2001-12-01

295

Subduction Zone Redox and the Deep Earth Cycles of Sulfur and Chalcophile Elements  

NASA Astrophysics Data System (ADS)

Subduction at convergent plate margins is a return flux to the mantle of rocks influenced by weathering, hydrothermal activity, atmospheric exchange, or bio-mineralization in the exosphere. The latter exogenic processes modify the long-term abundance and behaviour of certain elements in the deeper earth that can be traced over time in the chemistry of mantle-derived magmas. The redox budget of subduction is controlled by the flux of oxidized versus reduced forms of Fe, S, H, or C, and impacts the long-term evolution of oxygen on the planet, critical for life in the exosphere. In particular, the sulfur cycle is specifically tied to the evolution of oxygen on Earth's surface over time and critical to biogeochemical cycles on the surface. The behaviour of sulfur in the exogenic system is well-studied and fairly well understood using sedimentary records. An originally sulfidic ocean on Earth gave way with time and oxygenation to one that is sulfate dominated over the last two billion years. In contrast, far less is known of the deep earth cycle of S, and more so its history. The record of the endogenic cycle can only be monitored via what comes out of the mantle (magmas and their gases), or what goes down via subduction (hydrothermally-altered or weathered subducted lithosphere). Interest in the endogenic cycle of S is not new but several outstanding conundrums remain for sulfur in arc magmas that point to the importance of the subduction process. A hitherto ignored component of the paradox of the sulfur cycle is the sedimentary veneer that sits atop the subducted oceanic basalt crust. Compilations show only 0.12 wt% S in altered ocean basalt crust, but up to 10 times that amount in oceanic sediments, tied to their Fe content (in pyrite). These abundances may seem trivial, but the behaviour of this small amount of S in subduction is not fully appreciated and its oxidation potential in the arc mantle is enormous. The conversion of subducted sulfide to sulfate is a 8-electron change in redox state, with significant oxidation/ reduction capacity. The concomitant higher fO2 can in turn facilitate the mobility and/or extraction of chalcophile metals from the arc mantle into magmas by the melting process in arcs. Sedimentary records show that through most of Earth's history sulfur has mostly been subducted in reduced form as sulfide. The fate of sulfide in ocean sediments during subduction (and subsequent dehydration or melting) has not been thoroughly investigated, nor its interplay with other redox couples (C, H, Fe) in sediments, subducted basalt or in the mantle. I examine the redox controls on sulfate versus sulfide stability in subducted oceanic crust, and their disposition relative to other redox couples in the mantle. Sulfate-sulfide equilibria impact the fate of sulfur and chalcophile elements in subducted lithologies, especially if dehydrated or melted depending on a variety subduction P-T trajectories. In this light, new high P-T experiments show the utility of Cu as a proxy for S in the subduction system . These proxies can potentially be applied to examine the deep S cycle, subduction redox and its role in arc magmatism over geologic time.

Canil, D.

2013-12-01

296

Determination of {sup 90}Sr, {sup 137}Cs, and alkali/alkaline earth elements in nuclear waste by ion chromatography and liquid scintillation counting  

SciTech Connect

Ion chromatography (IC) is utilized in this study in a dual role: to rapidly isolate the major radioactive components ({sup 90}Sr and {sup 137}Cs) of nuclear waste prior to measurement of their beta-particle activities, and to simultaneously separate and measure significant nonradioactive constituents (alkali metal and alkaline earth elements) of the matrix. Samples were separated on a standard, commercial IC system modified for radioactive operation. The nonradioactive elements were measured by conductivity in a {open_quotes}suppressed{close_quotes} eluent. During the analysis {sup 90}Sr and {sup 137}Cs were collected as radiochemically pure fractions in the effluent from the conductivity detector and subsequently measured by liquid scintillation counting (LSC). The separation and counting can be performed in about 30 min with a precision of 1-2%. In a column cleaning step {sup 90}Y and other actinides were collected directly from the separation column in 1 M HCl. The suppression module was found to spread the {sup 90}Sr-elution peak unless nonradioactive strontium carrier was added to bring the elemental concentration to {approx}60 mg/L. The injection volume of the IC sample loop was measured by injection of radioactive standard solutions of known specific activities to allow absolute determination of the radionuclide concentrations. Nearly pure alpha-particle spectra were obtained from actinides in some of the cleanup fractions, indicating the method can be extended to the alpha-particle-emitting transuranic activities.

Cadieux, J.R. Jr.; Salaymeh, S.R.; Griffin, H.C.

1996-11-01

297

Experimental determination of the partitioning behavior of rare earth and high field strength elements between pargasitic amphibole and natural silicate melts  

SciTech Connect

The primary goal of this investigation was to derive a set of expressions that can be used to calculate the amphibole-melt partitioning behavior of the rare earth elements (REE) and the high field strength elements (HFSE) in natural systems. To supplement the existing data set on basaltic systems, the authors conducted experiments on systems where amphibole was in equilibrium with dacitic, tonalitic and low Si rhyolitic melts. These experiments, doped with La, Sm, Gd, Lu, Ta, Nb, Y, Zr, and Hf, were run at pressures of 2 and 5 kbar, temperatures between 900 C and 945 C, and oxidation conditions ranging from QFM-1 to NiNiO+1. The partitioning data obtained in this study were combined with published data to calculate two sets of expressions describing trace element partitioning. Partition coefficients calculated from the expressions derived in this study were used to model the partial melting and fractional crystallization of a hypothetical amphibolite and hydrous melt, respectively. Fractionation and/or melting in amphibole-bearing systems produces a magma with a convex upward REE pattern, a characteristic common to many hornblende-bearing dacites. However, the removal or addition of an amphibole component cannot produce the strong HFSE depletion relative to the REE observed in many arc magmas.

Hilyard, M.; Nielsen, R.L.; Beard, J.S.; Patino-Douce, A.; Blencoe, J.

2000-03-01

298

Earth  

NSDL National Science Digital Library

This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet Earth. These data include planet size, orbit facts, distance from the Sun, rotation and revolution times, temperature, atmospheric composition, density, surface materials and albedo. Images with descriptions show Earth features such as the Ross Ice Shelf in Antarctica, Simpson Desert in Australia, Mt. Etna in Sicily, the Cassiar Mountains in Canada, the Strait of Gibraltar, Mississippi River, Grand Canyon, Wadi Kufra Oasis in Libya, and Moon images such as Hadley Rille, Plum Crater, massifs and Moon rocks. These images were taken with the Galileo Spacecraft and by the Apollo missions.

299

Investigating the Partitioning of Inorganic Elements Consumed by Humans between the Various Fractions of Human Wastes: An Alternative Approach  

NASA Technical Reports Server (NTRS)

The elemental composition of food consumed by astronauts is well defined. The major elements carbon, hydrogen, oxygen, nitrogen and sulfur are taken up in large amounts and these are often associated with the organic fraction (carbohydrates, proteins, fats etc) of human tissue. On the other hand, a number of the elements are located in the extracellular fluids and can be accounted for in the liquid and solid waste fraction of humans. These elements fall into three major categories - cationic macroelements (e.g. Ca, K, Na, Mg and Si), anionic macroelements (e.g. P, S and Cl and 17 essential microelements, (e.g. Fe, Mn, Cr, Co, Cu, Zn, Se and Sr). When provided in the recommended concentrations to an adult healthy human, these elements should not normally accumulate in humans and will eventually be excreted in the different human wastes. Knowledge of the partitioning of these elements between the different human waste fractions is important in understanding (a) developing waste separation technologies, (b) decision-making on how these elements can be recovered for reuse in space habitats, and (c) to developing the processors for waste management. Though considerable literature exists on these elements, there is a lack of understanding and often conflicting data. Two major reasons for these problems include the lack of controlled experimental protocols and the inherently large variations between human subjects (Parker and Gallagher, 1988). We have used the existing knowledge of human nutrition and waste from the available literature and NASA documentation to build towards a consensus to typify and chemically characterize the various human wastes. It is our belief, that this could be a building block towards integrating a human life support and waste processing in a closed system.

Wignarajah, Kanapathipillai; Pisharody, Suresh; Fisher, John W.

2003-01-01

300

Trace Element Distributions and Size Fractionation in the Edmond Hydrothermal Plume, Central Indian Ridge  

NASA Astrophysics Data System (ADS)

Because cycling of the entire ocean volume through hydrothermal plumes is rapid relative to thermohaline circulation (order 103 years), understanding the processes active within these plumes is crucial if we are to assess their impact on global geochemical cycles. Preliminary results from hydrothermal plume particle analyses at the Kairei and Edmond systems (Indian Ocean) have indicated that key processes, previously identified to be important in the Atlantic Ocean, also appear broadly applicable to the Indian Ocean. This was not immediately expected because parallel work has shown that the rate of dissolved iron (II) oxidation in hydrothermal plumes decreases systematically from the Atlantic to the Indian and Pacific Oceans. Here, we examine dissolved-particulate trace metal distributions in greater detail within one Indian Ocean plume (Edmond), together with the complementary vent-fluid data, to investigate these processes further. Upon oxidation, dissolved iron (II) initially forms colloidal iron (III) which then aggregates to form particulate iron (III) - the oxyhydroxide particles which apparently co-precipitate and adsorb dissolved metals from the surrounding seawater. What has remained unstudied, however, is the role that colloidal rather than aggregated particulate Fe may play in these systems. To investigate this we have combined studies of large-volume plume-particle samples (1.0? m filters) with a series of dissolved, colloidal and finer-grained particles collected using a CTD-rosette. Here, we will discuss the distributions of Fe and the relative fractionations of Mn, Cu (representative of the chalcophile elements) and P (representative of the oxyanions) within and between different hydrothermal "pools": dissolved, colloidal, fine particles and coarse particles as determined from filtration through 0.1, 0.4 and 1.0? m filters.

Sands, C. M.; Connelly, D. P.; Green, D.; German, C. R.; Statham, P. J.; Gallant, R.; von Damm, K.

2004-12-01

301

Fractionation of highly siderophile elements in refertilized mantle: Implications for the Os isotope composition of basalts  

NASA Astrophysics Data System (ADS)

Highly fertile lherzolite and spinel websterite in the Ronda peridotite massif are enriched in Pt and Pd compared to Os, Ir, Ru and Re. The fractionation of the highly siderophile elements (HSE) in these rocks was produced by reaction of melt with their peridotite and pyroxenite precursors. Modeling indicates that upon reaction primary HSE hosts were dissolved and magmatic sulphides precipitated, largely erasing the original HSE signature of reacting protoliths. The budget of HSE in the melt was controlled by sulphide-silicate partitioning or entrainment of molten sulphide in silicate melt. Rhenium was likely removed from precursor peridotite and pyroxenite by previous melt extraction. Refertilization of peridotite by melts increased Al2O3, CaO, Pt, Pd contents and 187Os/188Os beyond typical values for mantle peridotite and the primitive upper mantle. The interaction of melts with residual peridotite and pyroxenite, as illustrated in the Ronda massif, can generate radiogenic-Os-enriched domains in the mantle with high melt productivity, higher Pt/Os and Pt/Re than common peridotite, and lower Re/Os than typical pyroxenite. As also previously proposed for pyroxenites, these “hybrid” domains can account for the difference in Os isotope compositions between many basalts (e.g., MORB and OIB) and common depleted mantle peridotites. Moreover, the presence of these enriched hybrid components in the mantle, evolved over sufficient timescales and in geologically reasonable proportions, may account for the 186Os-187Os enrichment of plume lavas without requiring a chemical contribution from the core.

Marchesi, Claudio; Dale, Christopher W.; Garrido, Carlos J.; Pearson, D. Graham; Bosch, Delphine; Bodinier, Jean-Louis; Gervilla, Fernando; Hidas, Károly

2014-08-01

302

Rare Earth Element Tracing for Bamsar, Revesht and Nezam-Abad Tungsten Deposits in Central Iran  

NASA Astrophysics Data System (ADS)

Bamsar, Revesht and Nezam-Abad tungsten deposits are located southwest of Shazand in central Iran. Rare Earth Element (REE) and other trace elements in samples of scheelite (CaWO4) from these deposits have been determined by Neutron Activation Analysis in order to constrain the composition and sources of the mineralizing fluids. Paleozoic and Triassic volcano-sedimentary rocks and upper Triassic-Jurassic detrital-chemical and volcanic units outcrop in the Shazand region. The intrusives in the region have granitic and granodioritic compositions that have caused metamorphic haloes in the upper Triassic-Jurassic units. Six ore-bearing skarn horizons have been identified at Bamsar, while granodioritic intrusives host vein-type mineralization at Revesht and Nezam-Abad. Revesht and Nezam-Abad scheelites have higher total REE and Na concentrations than Bamsar samples. Bamsar scheelites show flat chondrite-normalized REE (REEN) patterns, whereas scheelites from Revesht and Nezam-Abad exhibit hump-shaped REEN patterns with maximum REEN concentrations displaced towards Dy. Following the findings of Ghaderi et al. (1999) on scheelites from Western Australian gold deposits, it is suggested that Bamsar scheelites have variable Eu anomalies and trivalent REE concentrations and thus appear to contain mostly Eu2+ and to have formed under reduced conditions. Revesht and Nezam-Abad scheelites, on the other hand, exhibit no changes in the size of the Eu anomaly with REE concentration, implying a predominance of Eu3+ and crystallization under relatively oxidized conditions. Bamsar scheelites have (Ce/Lu)N > 1 and are interpreted to have crystallized from LREE-enriched fluids, whereas Revesht and Nezam-Abad scheelites with (Ce/Lu)N < 1 formed from LREE-depleted fluids. The elevated Na contents of Revesht and Nezam-Abad scheelites compared with Bamsar samples, suggest crystallization from hydrothermal fluids with higher Na activities. Reference: Ghaderi, M., Palin, J.M., Campbell, I.H., & Sylvester, P.J. (1999): Rare earth element systematics in scheelite from hydrothermal gold deposits in the Kalgoorlie-Norseman region, Western Australia. Economic Geology, v. 94, p. 423-437.

Ghaderi, M.

2001-12-01

303

Using rare earth elements for the identification of the geographic origin of food  

NASA Astrophysics Data System (ADS)

The European Union defined regimes within the Protected Geographical Status (PGS) framework to protect names of regional food specialities. Thus only food produced in a specific geographical area with a specific way of production or quality can be protected by a protected geographical indication (PGI) label. As such Styrian Pumpkin Seed Oil has been approved with this label, but as with many other high priced regional specialities, fraud cannot be excluded or nor identified. Thus the aim of this work is, to develop an analytical method for the control of the geographic origin of pumpkin seed oil and also to test the method for other protected products. The development of such a method is not only of interest for scientists, but also of importance for the consumer wanting to know the origin of the food products and the assurance of the purity and quality. The group of rare earth elements (REE) in plants also have a characteristic distribution pattern similar to upper crustal REE distributions. Since the REE concentrations are extremely low in pumpkin seed oil (ppt to low ppb), ICP-MS was the only sensitive tool able to produce validated results. The carrier of the REE are most likely small particles distributed within the pumpkin seed oil. Unlike, e.g., olive oil, pumpkin seed oil is bottled and sold unfiltered, which makes this Styrian speciality an interesting sampling target. As pumpkin seed oils from different geographic origin show variable trace element and rare earth distribution patterns, is should possible to trace the origin of these oils. In the current project pumpkin seeds from different regions in Austria and from abroad were sampled. The trace element patterns in the extracted oil of these seeds were determined and a preliminary classification with discriminate analysis was successfully done on a statistical basis. In addition to the study of the geographic origin it was demonstrated that REE distribution patterns can also be used for the identification of adulteration of high priced pumpkin seed oil with cheap neutral tasting refined oils. Interestingly enough, the variations of the REE patterns between oils from different regions are much more pronounced than their host soils. Thus we assume that microbiological processes in the rhizosphere are in control of the REE uptake into the plant. Regional variations of the microbiological composition of the soils and probably not only a priori the bulk soil composition of the minerals in the soil are the cause of the regional variations making it possible to identify the geographic origin of pumpkin seeds and as a consequence the pumpkin seed oil.

Meisel, T.; Bandoniene, D.; Joebstl, D.

2009-04-01

304

Road-deposited sediments in an urban environment: A first look at sequentially extracted element loads in grain size fractions.  

PubMed

Sediments stored in urban drainage basins are important environmental archives for assessing contamination. Few studies have examined the geochemical fractionation of metals in individual grain size classes of solid environmental media. This is the first study of road sediments to quantify the mass loading of Al, Cu, Pb, and Zn in individual grain size classes (<63?m to 1000-2000?m) and partition contributions amongst four sequentially extracted fractions (acid extractable, reducible, oxidizable, and residual). The optimized BCR sequential extraction procedure was applied to road sediments from Palolo Valley, Oahu, Hawaii. Road sediments from this non-industrialized drainage basin exhibited significant enrichment in Cu, Pb, and Zn. Metal mass loading results indicate that the <63?m grain size class dominated almost all fraction loads for a given element. The residual fraction dominated the Al loading for this geogenic element. The reducible fraction, associated with Fe and Mn oxides, was the most important component for Cu, Pb, and Zn loading. These results have direct implications for environmental planners charged with reducing sediment-associated contaminant transport in urbanized drainage basins. PMID:22609391

Sutherland, Ross A; Tack, Filip M G; Ziegler, Alan D

2012-07-30

305

A chemical-spectrochemical method for the determination of rare earth elements and thorium in cerium minerals  

USGS Publications Warehouse

In a combined chemical-spectrochemical procedure for quantitatively determining rare earth elements in cerium minerals, cerium is determined volumetrically, a total rare earths plus thoria precipitate is separated chemically, the ceria content of the precipitate is raised to 80??0 percent by adding pure ceria, and the resulting mixture is analyzed for lanthanum, praseodymium, neodymium, samarium, gadolinium, yttrium, and thorium spectrochemically by means of the d.c. carbon arc. Spectral lines of singly ionized cerium are used as internal standard lines in the spectrochemical determination which is patterned after Fassel's procedure [1]. Results of testing the method with synthetic mixtures of rare earths and with samples of chemically analyzed cerium minerals show that the coefficient of variation for a quadruplicate determination of any element does not exceed 5??0 (excepting yttrium at concentrations less than 1 percent) and that the method is free of serious systematic error. ?? 1954.

Rose, Jr. , H. J.; Murata, K. J.; Carron, M. K.

1954-01-01

306

Studies on Microbial Heavy Metal Retention from Uranium Mine Drainage Water with Special Emphasis on Rare Earth Elements  

Microsoft Academic Search

Microbial heavy metal retention was studied using seepage water sampled from a former uranium mining site in Eastern Thuringia, Germany. The seepage water has a low pH and contains high concentrations of metals, including uranium, rare earth elements (REE), and other heavy metals. Microbial influence on sorption and\\/or active uptake of heavy metals was studied using REE patterns. Incubation of

D. Merten; E. Kothe; G. Büchel

2004-01-01

307

Crystal-chemical controls on rare-earth element concentrations in fossil biogenic apatites and implications for paleoenvironmental reconstructions  

Microsoft Academic Search

Fossil biogenic apatites display rare-earth element (REE) patterns which have been proposed to reflect environmental and biological controls on past seawater composition. These patterns can be separated in two groups: (1) patterns that are similar to those of open ocean and epicontinental waters and (2) patterns that exhibit a strong enrichment in intermediate REE (bell-shaped patterns). Because REE trapping in

Bruno Reynard; Christophe Lécuyer; Patricia Grandjean

1999-01-01

308

Geochemistry of the rare-earth elements and uranium in the acidic Berkeley Pit lake, Butte, Montana  

Microsoft Academic Search

Filtered (0.45 ?m) and nonfiltered concentrations of rare-earth elements (REE), U, Zr, Th, Ba, Sc, and Y were measured as a function of depth in the Berkeley Pit lake, a large acidic mining lake in Butte, MT. The REE show very little variation with depth, apart from a slight concentration near the surface, presumably due to evaporation. The REE profiles

Christopher H. Gammons; Scott A. Wood; James P. Jonas; James P. Madison

2003-01-01

309

Nondestructive neutron activation analysis of rare earth elements in hot spring water samples in Kusatsu-shirane area, Japan  

Microsoft Academic Search

Hot spring water samples have been analyzed for their rare earth elements (REE's) determination by the nondestructive neutron activation method. Five REE's, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REE's, however,

T. Honda; T. Nozaki; T. Ossaka; T. Oi; H. Kakihana

1988-01-01

310

Geochemical Studies of Rare Earth Elements in the Portuguese Pyrite Belt, and Geologic and Geochemical Controls on Gold Distribution.  

National Technical Information Service (NTIS)

Geochemical and geologic studies were conducted by the U.S. Geological Survey and the Servicos Geologicos de Portugal in the Portuguese Pyrite Belt in southern Portugal during 1987 and 1988. The studies included (1) rare earth element distributions, (2) t...

D. J. Grimes R. L. Earhart D. de Carvalho V. Oliveira J. T. Oliveira

1998-01-01

311

Overview of Rare Earth Element Investigations in Acid Waters of U. S. Geological Survey Abandoned Mine Lands Watersheds  

Microsoft Academic Search

The geochemistry of rare earth element (REE) variations in acid waters is being studied as part of the U. S. Geological Survey Abandoned Mine Lands Initiative in two pilot watersheds, upper Animas, Colorado and Boulder, Montana. The following objectives are under investigation: (1) comparison of acid mine waters and naturally acidic springs, (2) determination of whether the dominant control on

Philip L. Verplanck; D. Kirk Nordstrom; Howard E. Taylor

312

Geochemistry of alkaline earth elements (Mg, Ca, Sr, Ba) in the surface sediments of the Yellow Sea  

Microsoft Academic Search

The concentrations of alkaline earth elements were measured in the surface sediments of the Yellow Sea in an attempt to establish their sources from horizontal distributions. The maximum concentrations of Mg are found in the central Yellow Sea, and its horizontal distribution is mainly controlled by quartz dilution. The concentrations of Ca and Sr increase toward the southeastern Yellow Sea

Guebuem Kim; Han-Soeb Yang; Thomas M. Church

1999-01-01

313

Fractionation of fluorine, chlorine and other trace elements during differentiation of a tholeiitic magma  

Microsoft Academic Search

The elements F, Cl, Ni, Co, Cu, Ga, Sc, Cr, V, Ba and Sr have been determined in two drill cores through a differentiated tholeiitic dolerite sill from Tasmania. A multivariate statistical technique is employed to demonstrate the occupancy of hydroxyl lattice sites by both chlorine and fluorine. Consideration of trace-element\\/major-element ratios suggests that, in these dolerites. Ni occupies Fe

L. Greenland; J. F. Lovering

1966-01-01

314

Distribution behavior of uranium, neptunium, rare-earth elements ( Y, La, Ce, Nd, Sm, Eu, Gd) and alkaline-earth metals (Sr,Ba) between molten LiCl?KCI eutectic salt and liquid cadmium or bismuth  

Microsoft Academic Search

Distribution coefficients of uranium neptunium, eight rare-earth elements (Y, La, Ce, Pr, Nd, Sm, Eu and Gd) and two alkaline-earth metals (Sr and Ba) between molten LiCl-KCI eutectic salt and either liquid cadmium or bismuth were measured at 773 K. Separation factors of trivalent rare-earth elements to uranium or neptunium in the LiCl-KCl\\/Bi system were by one or two orders

M. Kurata; Y. Sakamura; T. Hijikata; K. Kinoshita

1995-01-01

315

Rare-earth elements enrichment of Pacific seafloor sediments: the view from volcanic islands of Polynesia  

NASA Astrophysics Data System (ADS)

Rare-earth elements (REEs) are key metals for «green» technologies such as energy saving lamps or permanent magnets used in, e.g., wind turbines, hard disk drives, portable phone or electric or hybrid vehicles. Since several years, world demand for these metals is therefore drastically increasing. The quasi-monopolistic position of China, which produces around 95 % of global REEs production, generates risks for the industries that depend on a secure supply of REEs. In response, countries are developing and diversifying their supply sources, with new mining projects located outside China and efforts in the area of REEs recycling. Most of these projects focus on deposits related to carbonatites and alkaline-peralkaline magmatism, which are generally enriched in light REEs (LREEs) compared to the heavy REEs (HREEs)-enriched deposits of the ion-adsorption types, located in southern China. However, a recent study revealed new valuable resources corresponding to seafloor sediments located in the south-eastern and north-central Pacific. The deep-sea mud described by these authors show a higher HREE/LREE ratio than ion-adsorption deposits, a feature which significantly increases their economic interest. The authors suggest mid-ocean ridge hydrothermal activity as an explanation to this anomalous enrichment. However, several contributions have documented considerable REEs enrichment in basalts and peridotitic xenoliths from French Polynesia. Several arguments have been exposed in favour of a supergene origin, with a short migration, suggesting that REEs were collected from weathered basalts. The Tahaa volcanic island (Sous-le-Vent Island, Society Archipelago, French Polynesia) is the first location where such enrichment has been described. New petrographic and mineralogical investigations confirm a supergene mobilization of this abnormal occurrence. REE-bearing minerals (mainly phosphates of the rhabdophane group) are primarily located within basalt vesicles but also in crack that cross-cut the calcite filling the vesicles or the volcanic glass. They are also closely associated with Ni-Mg bearing phyllosilicates, which appear to nucleate from alteration of olivine and clinopyroxenes. Further investigations are done to evidence and confirm an anterior magmatic enrichment. On the basis of these observations, we believe that the anomalous enrichment observed in seafloor sediments could derive from abnormally-rich provinces corresponding to aerial basaltic formations from oceanic islands primarily enriched during weathering processes (Melleton et al., 2014). Melleton et al. (2014). Rare-earth elements enrichment of Pacific sea-floor sediments: the view from volcanic islands of Polynesia. In preparation.

Melleton, Jérémie; Tuduri, Johann; Pourret, Olivier; Bailly, Laurent; Gisbert, Thierry

2014-05-01

316

Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems  

NASA Astrophysics Data System (ADS)

Rare earth element (REE) and yttrium (Y) concentrations were measured in fluids collected from deep-sea hydrothermal systems including the Mid-Atlantic Ridge (MAR), i.e., Menez Gwen, Lucky Strike, TAG, and Snakepit; the East Pacific Rise (EPR), i.e., 13°N and 17-19°S; and the Lau (Vai Lili) and Manus (Vienna Woods, PacManus, Desmos) Back-Arc Basins (BAB) in the South-West Pacific. In most fluids, Y is trivalent and behaves like Ho. Chondrite normalized Y-REE (Y-REE N) concentrations of fluids from MAR, EPR, and two BAB sites, i.e., Vai Lili and Vienna Woods, showed common patterns with LREE enrichment and positive Eu anomalies. REE analysis of plagioclase collected at Lucky Strike strengthens the idea that fluid REE contents, are controlled by plagioclase phenocrysts. Other processes, however, such as REE complexation by ligands (Cl -, F - SO 42-), secondary phase precipitation, and phase separation modify REE distributions in deep-sea hydrothermal fluids. REE speciation calculations suggest that aqueous REE are mainly complexed by Cl - ions in hot acidic fluids from deep-sea hydrothermal systems. REE concentrations in the fluid phases are, therefore, influenced by temperature, pH, and duration of rock-fluid interaction. Unusual Y-REE N patterns found in the PacManus fluids are characterized by depleted LREE and a positive Eu anomaly. The Demos fluid sample shows a flat Y-REE N pattern, which increases regularly from LREE to HREE with no Eu anomaly. These Manus Basin fluids also have an unusual major element chemistry with relatively high Mg, SO 4, H 2S, and F contents, which may be due to the incorporation of magmatic fluids into heated seawater during hydrothermal circulation. REE distribution in PacManus fluids may stem from a subseafloor barite precipitation and the REE in Demos fluids are likely influenced by the presence of sulfate ions.

Douville, Eric; Bienvenu, Philippe; Charlou, Jean Luc; Donval, Jean Pierre; Fouquet, Yves; Appriou, Pierre; Gamo, Toshitaka

1999-03-01

317

Microdistributions and petrogenetic implications of rare earth elements in polymict ureilites  

NASA Astrophysics Data System (ADS)

Polymict ureilites contain various mineral and lithic clasts not observed in monomict ureilites, including plagioclase, enstatite, feldspathic melt clasts and dark inclusions. This paper investigates the microdistributions and petrogenetic implications of rare earth elements (REEs) in three polymict ureilites (Elephant Moraine (EET) 83309, EET 87720 and North Haig), focusing particularly on the mineral and lithic clasts not found in monomict ureilites. As in monomict ureilites, olivine and pyroxene are the major heavy (H)REE carriers in polymict ureilites. They have light (L)REE-depleted patterns with little variation in REE abundances, despite large differences in major element compositions. The textural and REE characteristics of feldspathic melt clasts in the three polymict ureilites indicate that they are most likely shocked melt that sampled the basaltic components associated with ureilites on their parent body. Simple REE modeling shows that the most common melt clasts in polymict ureilites can be produced by 20-30% partial melting of chondritic material, leaving behind a ureilitic residue. The plagioclase clasts, as well as some of the high-Ca pyroxene grains, probably represent plagioclase-pyroxene rock types on the ureilite parent body. However, the variety of REE patterns in both plagioclase and melt clasts cannot be the result of a single igneous differentiation event. Multiple processes, probably including shock melting and different sources, are required to account for all the REE characteristics observed in lithic and mineral clasts. The C-rich matrix in polymict ureilites is LREE-enriched, like that in monomict ureilites. The occurrence of Ce anomalies in C-rich matrix, dark inclusions and the presence of the hydration product, iddingsite, imply significant terrestrial weathering. A search for 26Mg excesses, from the radioactive decay of 26Al, in the polymict ureilite EET 83309 was negative.

Guan, Yunbin; Crozaz, Ghislaine

2001-08-01

318

Oxidation Resistance of Fe80Cr20 Alloys Treated by Rare Earth Element Ion Implantation  

NASA Astrophysics Data System (ADS)

The oxidation behaviour of newly developed process of Fe80Cr20 alloy was studied as a function of temperature in the range 1173-1273 K for up to 100 h in flowing air, which corresponds to the Solid Oxide Fuel Cell (SOFC) environment operating conditions. The effects of rare earth element implantation and depth profile on the oxidation behaviour of specimens were analyzed based on oxide morphology and microstructure. Characterisation of the oxide phase products after oxidation was made by X-ray diffraction (XRD). The surface morphology of oxide scales was examined using the scanning electronic microscope (SEM) with energy-dispersive X-ray analysis (EDX). The rate constant of thermal oxidation was determined using Wagner method. Experimental results show that the specimens implanted with lanthanum have remarkably enhanced the oxidation resistance. The oxidation test indicates that the newly developed process of Fe80Cr20 implantation with lanthanum ions exhibit considerably greater improvement in the oxidation resistance compared to the specimens implanted with titanium. The newly developed process of Fe80Cr20 milled for 60h show better oxidation resistance compared to specimens milled for 40h.

Sebayang, Darwin; Khaerudini, Deni S.; Saryanto, H.; Hasan, Sulaiman; Othman, M. A.; Untoro, Puji

2011-10-01

319

Rare earth element distributions and trends in natural waters with a focus on groundwater.  

PubMed

Systematically varying properties and reactivities have led to focused research of the environmental forensic capabilities of rare earth elements (REE). Increasing anthropogenic inputs to natural systems may permanently alter the natural signatures of REE, motivating characterization of natural REE variability. We compiled and analyzed reported dissolved REE concentration data over a wide range of natural water types (ground-, ocean, river, and lake water) and groundwater chemistries (e.g., fresh, brine, and acidic) with the goal of quantifying the extent of natural REE variability, especially for groundwater systems. Quantitative challenges presented by censored data were addressed with nonparametric distributions and regressions. Reported measurements of REE in natural waters range over nearly 10 orders of magnitude, though the majority of measurements are within 2-4 orders of magnitude, and are highly correlated with one another. Few global correlations exist among dissolved abundance and bulk solution properties in groundwater, indicating the complex nature of source-sink terms and the need for care when comparing results between studies. This collection, homogenization, and analysis of a disparate literature facilitates interstudy comparison and provides insight into the wide range of variables that influence REE geochemistry. PMID:24628583

Noack, Clinton W; Dzombak, David A; Karamalidis, Athanasios K

2014-04-15

320

On the non-uniform distribution of the angular elements of near-Earth objects  

NASA Astrophysics Data System (ADS)

We examine the angular distributions of near-Earth objects (NEOs) which are often regarded as uniform. The apparent distribution of the longitude of ascending node, ?, is strongly affected by well-known seasonal effects in the discovery rate of NEOs. The deviation from the expected ?-periodicity in the apparent distribution of ? indicates that its intrinsic distribution is slightly enhanced along a mean direction, ??=111°; approximately 53% of NEOs have ? values within ±90° of ??. We also find that each subgroup of NEOs (Amors, Apollos and Atens) has different observational selection effects which cause different non-uniformities in the apparent distributions of their arguments of perihelion ?, and longitudes of perihelion ?. For their intrinsic distributions, our analysis reveals that the Apollo asteroids have non-uniform ? due to secular dynamics associated with inclination-eccentricity-? coupling, and the Amors' ? distribution is peaked towards the secularly forced eccentricity vector. The Apollos' ? distribution is axial, favoring values near 0° and 180°; the two quadrants centered at 0° and 180° account for 55% of the Apollos' ? values. The Amors' ? distribution peaks near ??=4°; 61% of Amors have ? within ±90° of this peak. We show that these modest but statistically significant deviations from uniform random distributions of angular elements are owed to planetary perturbations, primarily Jupiter's. It is remarkable that this strongly chaotic population of minor planets reveals the presence of Jupiter in its angular distributions.

JeongAhn, Youngmin; Malhotra, Renu

2014-02-01

321

Recycling rare earth elements from industrial wastewater with flowerlike nano-Mg(OH)(2).  

PubMed

Treatment of wastewater containing low-concentration yet highly-expensive rare earth elements (REEs) is one of the vital issues in the REEs separation and refining industry. In this work, the interaction and related mechanism between self-supported flowerlike nano-Mg(OH)2 and low-concentration REEs wastewater were investigated. More than 99% REEs were successfully taken up by nano-Mg(OH)2. Further analysis revealed that the REEs could be collected on the surface of Mg(OH)2 as metal hydroxide nanoparticles (<5 nm). An ion-exchange model was proposed as a critical factor for both guaranteeing the reaction speed and maintaining the self-supported structure of the materials. In addition, a method was developed to further separate the immobilized REEs and the residual magnesium hydroxide by varying the solution pH. In a pilot-scale experiment, the REEs from practical wastewater were immobilized effectively at a high flow rate. We anticipate this work can provide a good example for the recycling of valuable REEs in practical industrial applications. PMID:24032646

Li, Chaoran; Zhuang, Zanyong; Huang, Feng; Wu, Zhicheng; Hong, Yangping; Lin, Zhang

2013-10-01

322

Gupta potential for rare earth elements of the fcc phase: lanthanum and cerium  

NASA Astrophysics Data System (ADS)

The potential parameters for a Gupta-type many-body potential are fitted for the first two rare earth elements, La and Ce. The experimental cohesive energies, lattice parameters and elastic constants of ?-La and ?-Ce solids of the face-centered cubic (fcc) phase are well reproduced. The theoretical P-V curves, sound velocities and Debye temperatures of ?-La and ?-Ce solids are in reasonable agreement with experimental data. The vacancy formation energies and surface energies are also predicted. In particular, the phonon dispersion relationship and vibrational frequencies at high symmetric points within the first Brillouin zone from our potential are consistent with experimental ones. Molecular dynamics simulation are performed to determine the melting temperature of La and Ce solids as well as the radial distribution function of liquid La, which are also in line with experimental data. All these agreements indicate the validity of the current set of potential parameters. Thus, the Gupta potential developed here would be useful in future simulation of La, Ce solids and their alloys.

Fu, Jie; Zhao, Jijun

2013-09-01

323

[Research on the cytotoxic and genotoxic effects of rare-earth element holmium to Vicia faba].  

PubMed

Crystal of nitrate, made by the reaction of holmium trioxide and nitric acid, was dissolved in distilled water, thus diluted into gradient solution. Soaked in the solution for 6 hours (6h), the root tips of Vicia faba were then recovered and cultivated for 22 h and 24 h, respectively. By observing the change of root tips and calculating the frequency of micronucleus (FMN), the frequency of chromosomal aberrations(CAF) and mitosis index (MI),we find that the dosage below 4mg/L (expressed by concentration of holmium trioxide) could accelerate the growth of root tips of Vicia faba. CAF and FMN increased while MI decreased with the rise of concentrations. From it a dosage effect relationship is clearly seen. And it indicated that the rare earth element holmium has certain cytotoxic and genotoxic effects. Furthermore, the different recovery groups have different FMN, CAF and MI, and the difference lies in the fact that FMN of 22 h recovery group was lower than that of 24 h recovery group, while CAF and MI were higher than those of 24 h recovery group. The results suggest that the statistics of FMN should be made after that of CAF. PMID:15639987

Qu, Ai; Wang, Cheng-Run; Bo, Jun

2004-03-01

324

Composition and evolution of the eucrite parent body - Evidence from rare earth elements. [extraterrestrial basaltic melts  

NASA Technical Reports Server (NTRS)

Quantitative modeling of the evolution of rare earth element (REE) abundances in the eucrites, which are plagioclase-pigeonite basalt achondrites, indicates that the main group of eucrites (e.g., Juvinas) might have been produced by approximately 10% equilibrium partial melting of a single type of source region with initial REE abundances which were chondritic relative and absolute. Since the age of the eucrites is about equal to that of the solar system, extensive chemical differentiation of the eucrite parent body prior to the formation of eucrites seems unlikely. If homogeneous accretion is assumed, the bulk composition of the eucrite parent body can be estimated; two estimates are provided, representing different hypotheses as to the ratio of metal to olivine in the parent body. Since a large number of differentiated olivine meteorites, which would represent material from the interior of the parent body, have not been detected, the eucrite parent body is thought to be intact. It is suggested that the asteroid 4 Vesta is the eucrite parent body.

Consolmagno, G. J.; Drake, M. J.

1977-01-01

325

Elements of a new Global Water Strategy for the Group on Earth Observations  

NASA Astrophysics Data System (ADS)

In order to address the need to review the scope and direction of GEO activities related to water and to provide guidance for the post-2015 GEO planning, the Integrated Global Water Cycle Observations (IGWCO) Community of Practice and the Committee on Earth Observation Satellites (CEOS) are working together to develop a strategy for GEO water activities over the next decade. This presentation will review the elements of the strategy which include topics as comprehensive as user needs and engagement, water cycle observational systems, assessment of water quality, data issues, interoperability and integration of water information systems and capacity building. Impediments in the flow of information and technological capabilities from the providers of new technologies, innovations and data products to the end users will be explored in terms of the nature of these impediments and how they can be overcome. To be successful in GEO's framework of volunteerism, the water strategy should build on activities that are on-going in related programmes at the international and national levels. In addition, implementation of the strategy will need to be supported through new initiatives and policies that promote greater integration. Suggestions for achieving these goals will be outlined at the end of the talk.

Lawford, Richard; Koike, Toshio; Ochiai, Osamu; Cripe, Douglas

2013-04-01

326

New fission fragment distributions and r-process origin of the rare-earth elements.  

PubMed

Neutron star (NS) merger ejecta offer a viable site for the production of heavy r-process elements with nuclear mass numbers A?140. The crucial role of fission recycling is responsible for the robustness of this site against many astrophysical uncertainties, but calculations sensitively depend on nuclear physics. In particular, the fission fragment yields determine the creation of 110?A?170 nuclei. Here, we apply a new scission-point model, called SPY, to derive the fission fragment distribution (FFD) of all relevant neutron-rich, fissioning nuclei. The model predicts a doubly asymmetric FFD in the abundant A?278 mass region that is responsible for the final recycling of the fissioning material. Using ejecta conditions based on relativistic NS merger calculations, we show that this specific FFD leads to a production of the A?165 rare-earth peak that is nicely compatible with the abundance patterns in the Sun and metal-poor stars. This new finding further strengthens the case of NS mergers as possible dominant origin of r nuclei with A?140. PMID:24483647

Goriely, S; Sida, J-L; Lemaître, J-F; Panebianco, S; Dubray, N; Hilaire, S; Bauswein, A; Janka, H-T

2013-12-13

327

Influence of different bentonites on the rare earth element concentrations of clarified Romanian wines.  

PubMed

The rare earth element (REE) concentrations of 19 Romanian young wine samples originating from the Dealurile Moldovei viticulture area were determined by double focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) after microwave-assisted digestion with nitric acid. The determination of Eu was hampered by the BaO molecular interference. Generally, the red wine samples were more concentrated for REEs than the white wine samples studied. The REE concentrations of the four bentonites (Gelbenton, Evergel, BW200, Tükrös) determined after their fusion were higher by three orders of magnitude than those of the wine samples. After a simulated wine purification process performed with these bentonite samples and a red and white pool samples, the REE concentrations of the clarified wine samples increased by 1.2-1.5 times for red, and 1.3-3 times for white wines in case of the fibrous bentonite sample (Gelbenton), by about 2-5 times in case of the bentonite containing ovalbumin, caseine and gelatine (Evergel), meanwhile this factor was about 20-25 for Na bentonite powder samples (BW200, Tükrös). On basis of the chemometric evaluation using the REE concentrations as input data, the majority of the Feteasca wines belonged to the same cluster as well as the two Cabernet Sauvignon to another subcluster. The adequate choice of the bentonite may allow the use of REEs as fingerprints for determining the wine provenance. PMID:18970871

Mihucz, Victor G; Done, Carla J; Tatár, Eniko; Virág, István; Záray, Gyula; Baiulescu, Emil G

2006-12-15

328

LiYF4 (YLF) single crystals doped with rare-earth elements  

NASA Astrophysics Data System (ADS)

LiYF4 (YLF) is a very promising host material for lasers. Investigation of the spectroscopic and physical properties of YLF:Nd has suggested that this material may be a better candidate than Nd:YAG for generating short pulses with high peak power. This is a distinct advantage for many applications. Stimulated emission is attained at 1053 nm and 1047 nm. Also upconservation laser action in YLF and YLF:Er crystals is reported. More recently YLF doped with rare-earth elements has gained some attention. Pulsed room-temperature laser action at 2.06 micrometer has been achieved using YLF:Ho sensitized with Er and Tm. Using YLF:Pr blue light emission at 479 nm at room temperature was observed. Growth experiments of YLF:Nd crystals were carried by the Bridgman method. A vacuum furnace with cylindrical molybdenum heater and graphite crucible have been used. The temperature gradient of 25 degrees Celsius/cm has been achieved by using a stainless steel liner in the lower part of the furnace. The growth was performed in a nitrogen atmosphere. First crystals of YLF:Nd have been obtained.

Kowalczyk, E.; Kowalczyk, Z.; Grasza, K.; Gala, M.; Lukasiewicz, Tadeusz

1995-10-01

329

Determination of the rare-earth elements in geological materials by inductively coupled plasma mass spectrometry  

USGS Publications Warehouse

A method of analysis of geological materials for the determination of the rare-earth elements using the Inductively coupled plasma mass spectrometric technique (ICP-MS) has been developed. Instrumental parameters and factors affecting analytical results have been first studied and then optimized. Samples are analyzed directly following an acid digestion, without the need for separation or preconcentration with limits of detection of 2-11 ng/g, precision of ?? 2.5% relative standard deviation, and accuracy comparable to inductively coupled plasma emission spectrometry and instrumental neutron activation analysis. A commercially available ICP-MS instrument is used with modifications to the sample introduction system, torch, and sampler orifice to reduce the effects of high salt content of sample solutions prepared from geologic materials. Corrections for isobaric interferences from oxide ions and other diatomic and triatomic ions are made mathematically. Special internal standard procedures are used to compensate for drift in metahmetal oxide ratios and sensitivity. Reference standard values are used to verify the accuracy and utility of the method.

Lichte, F. E.; Meier, A. L.; Crock, J. G.

1987-01-01

330

A dual reciprocity boundary element formulation using the fractional step method for the incompressible Navier–Stokes equations  

Microsoft Academic Search

This paper presents a dual reciprocity boundary element solution method for the unsteady Navier–Stokes equations in two-dimensional incompressible flow, where a fractional step algorithm is utilized for the time advancement. A fully explicit, second-order, Adams–Bashforth scheme is used for the nonlinear convective terms. We performed numerical tests for two examples: the Taylor–Green vortex and the lid-driven square cavity flow for

Chang-Yong Choi; Elias Balaras

2009-01-01

331

More investigations into elemental fractionation resulting from laser ablation–inductively coupled plasma–mass spectrometry on glass samples  

Microsoft Academic Search

Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) experiments have been performed to determine if any portion of the observed elemental fractionation from 532 nm ablation of glass samples occurs in the ICP. A tubing insert has been made to remove the larger sized particles from the transfer tubing before they reach the ICP–MS and particles counter. The advantages of the tubing

Deborah J. Figg; Jon B. Cross; Chris Brink

1998-01-01

332

Rare earth element mineralogy, geochemistry, and preliminary resource assessment of the Khanneshin carbonatite complex, Helmand Province, Afghanistan  

USGS Publications Warehouse

There is increased concern about the future availability of rare earth elements (REE) because of China's dominance as the supplier of more than 95 percent of world REE output, their decision to restrict exports of rare earth products, and the rapid increase in world-wide consumption of rare earth product. As a result, countries such as the United States, Japan, and member nations of the European Union face a future of tight supplies and high prices for rare earth products unless other sources of REE are found and developed (Long and others, 2010; U.S. Geological Survey, 2011, p. 128-129, 184-185). We report and describe a significant new deposit of light rare earth elements (LREE), estimated at 1 Mt, within the Khanneshin carbonatite complex of south Afghanistan. The potential resource is located in a remote and rugged part of the igneous complex in a region previously identified by Soviet geologists in the 1970s. This report reviews the geologic setting of LREE deposit, presents new geochemical data documenting the grade of LREE mineralization, briefly describes the mineralogy and mineralogical associations of the deposit, and presents a preliminary estimate of LREE resources based on our current understanding of the geology.

Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Buttleman, Kim P.

2011-01-01

333

Fractionation of fluorine, chlorine and other trace elements during differentiation of a tholeiitic magma.  

NASA Technical Reports Server (NTRS)

Fluorine, chlorine and other trace elements determined through differentiated tholeiitic dolerite sill from Tasmania using statistical techniques, showing hydroxyl lattice sites by chlorine and fluorine

Greenland, L.; Lovering, J. F.

1966-01-01

334

Rare earth elements in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica  

NASA Astrophysics Data System (ADS)

We present data on the composition of water from Lake Vanda, Antarctica. Vanda and other lakes in the McMurdo Dry Valleys of Antarctica are characterized by closed basins, permanent ice covers, and deep saline waters. The meromictic lakes provide model systems for the study of trace metal cycling owing to their pristine nature and the relative simplicity of their biogeochemical systems. Lake Vanda, in the Wright Valley, is supplied by a single input, the Onyx River, and has no output. Water input to the lake is balanced by sublimation of the nearly permanent ice cap that is broken only near the shoreline during the austral summer. The water column is characterized by an inverse thermal stratification of anoxic warm hypersaline water underlying cold oxic freshwater. Water collected under trace-element clean conditions was analyzed for its dissolved and total rare earth element (REE) concentrations by inductively coupled plasma mass spectrometry. Depth profiles are characterized by low dissolved REE concentrations (La, Ce, <15 pM) in surface waters that increase slightly (La, 70 pM; Ce, 20 pM) with increasing depth to ˜55 m, the limit of the fresh oxic waters. Below this depth, a sharp increase in the concentrations of strictly trivalent REE (e.g., La, 5 nM) is observed, and a submaximum in redox sensitive Ce (2.6 nM) is found at 60- to 62-m depth. At a slightly deeper depth, a sharper Ce maximum is observed with concentrations exceeding 11 nM at a 67-m depth, immediately above the anoxic zone. The aquatic concentrations of REE reported here are ˜50-fold higher than previously reported for marine oxic/anoxic boundaries and are, to our knowledge, the highest ever observed at natural oxic/anoxic interfaces. REE maxima occur within stable and warm saline waters. All REE concentrations decrease sharply in the sulfidic bottom waters. The redox-cline in Lake Vanda is dominated by diffusional processes and vertical transport of dissolved species driven by concentration gradients. Furthermore, because the ultraoligotrophic nature of the lake limits the potential for organic phases to act as metal carriers, metal oxide coatings and sulfide phases appear to largely govern the distribution of trace elements. We discuss REE cycling in relation to the roles of redox reactions and competitive scavenging onto Mn- and Fe-oxides coatings on clay sized particles in the upper oxic water column and their release by reductive dissolution near the anoxic/oxic interface.

De Carlo, Eric Heinen; Green, William J.

2002-04-01

335

Source and mobility of Rare Earth Elements in a sedimentary aquifer system: Aquitaine basin (Southern France)  

NASA Astrophysics Data System (ADS)

The study of rare earth elements (REEs) in natural waters initially involved an examination of their occurrence and behavior in seawater and coastal waters such as estuaries. Since the 1990s, REE geochemistry has been applied to continental waters such as rivers and lakes and groundwaters. Rare earth elements) are of great interest because of their unique characteristics and have been used in the study of many geological processes like weathering and water-rock interaction processes, provenance of sediments, etc... With the evolution of analytical techniques like new generation ICP-MS, much attention had been paid towards the water geochemistry of REEs. However, there is a need of more investigations devoted to REEs in large groundwater systems, especially on the understanding of the distribution of REEs and their evolution in such systems. In this frame, large sedimentary aquifer systems often constitute strategic water resources for drinking water supply, agriculture irrigation and industry, but can also represent an energetic resource for geothermal power. Large water abstractions can induce complete modification of the natural functioning of such aquifer systems. These large aquifer systems thus require water management at the basin scale in order to preserve both water quantity and quality. The large Eocene Sand aquifer system of the Aquitaine sedimentary basin was studied through various hydrological, chemical and isotopic tools. This system extends over 116,000 km2 in the South west part of the French territory. The aquifer being artesian in the west of the district and confined with piezometric levels around 250-m depth in the east. The 'Eocene Sands', composed of sandy Tertiary sediments alternating with carbonate deposits, is a multi-layer system with high permeability and a thickness of several tens of metres to a hundred metres. The Eocene Sand aquifer system comprises at least five aquifers: Paleocene, Eocene infra-molassic sands (IMS), early Eocene, middle Eocene, and late Eocene. One important feature, in these confined systems isolated from anthropogenic influence, is the range in salinities by a factor of 10, from 250 mg/L up to 2.5 g/L. The ?REE, in the range 2-54 ng/L, with a dependence on salinity when expressed in % HCO3 or SO4, reflect the carbonate or evaporite source of REEs. The UCC normalized-REE patterns show a large variability as exemplified by the REE flat patterns-low SREE associated with salinity controlled by HCO3. In the present work, the REEs are investigated in terms of saturation indices, speciation modelling, REE patterns in order to recognize the aquifer type hosting groundwater and decipher the origin of the salinity of the groundwater as some part of the aquifer display in the groundwater concentration of chemical element exceeding the drinking water standard (SO4, F...). Such high concentrations of naturally-occurring substances (e.g. unaffected by human activities) can have negative impacts on groundwater thresholds and deciphering their origin by means of geochemical tools like REE is a remaining challenge.

Negrel, P. J.; Petelet-Giraud, E.; Millot, R.; Malcuit, E.

2011-12-01

336

Rare earth and trace element mobility in mid-crustal shear zones: insights from the Mont Blanc Massif (Western Alps)  

NASA Astrophysics Data System (ADS)

The behaviour of rare earth elements (REE) during fluid-rock interaction in mid-crustal shear zones has received little attention, despite their potential for mass balance calculation and isotopic tracing during deformation. In this study, several cases of large REE mobility during Alpine fluid-driven shear zone development in the pre-Alpine granitic basement of the Mont Blanc Massif are considered. On a regional scale, the undeformed granite compositions range within 5 wt% SiO 2 (70.5-75.3 wt%) and magmatic chemical variations are of the order of 10-20%, ascribed to minor effects of crystal fractionation. Major and trace element mobility observed in shear zones largely exceeds these initial variations. Shear zones developed a range of mineral assemblages as a result of shearing at mid-crustal depths (at ˜0.5 GPa, 400°C). Five main shear zone assemblages involve muscovite, chlorite, epidote, actinolite and calcite, respectively, as major phases. In most cases, selective enrichments of light or heavy REE (and Y, Ta, Hf) are observed. REE mobility is unrelated to deformation style (cataclastic, mylonitic), the intensity of strain, and to the shear zone's major metamorphic mineral assemblages. Instead, the changes in REE concentrations are ascribed to the alteration of pre-existing magmatic REE-bearing minerals during deformation-related fluid-rock interaction and to the syntectonic precipitation of metamorphic REE-bearing minerals (mainly monazite, bastnäsite, aeschynite and tombarthite). Minor proportions (<2%) of these accessory phases, with grain sizes mostly <20 ?m, account for enrichments of up to 5:1 compared to the initial granite whole-rock REE budget. The stability of the REE phases appears to be largely dependent on the altering fluid composition. REE mobility is ascribed to changes in pH and to the availability of CO 32-, PO 42-, and SO 42-ligands in the fluid. Such processes are likely to influence the mobility of REE, Y, Hf and Ta in shear zones.

Rolland, Yann; Cox, Stephen; Boullier, Anne-Marie; Pennacchioni, Giorgio; Mancktelow, Neil

2003-09-01

337

Evaporation thermodynamics of monotellurides of selected rare Earth and alkaline Earth elements, and an attempt to systematic correlation between the standard enthalpies of formation  

NASA Astrophysics Data System (ADS)

A contribution was made to improve the knowledge of the thermochemical characteristics of monotellurides (especially the binary lanthanoide monotelluride) by the determination of the enthalpies of formation, as well as to improve the production and analysis method of these compounds. The fundamentals for the thermodynamical quantities determination of rare earth and alkaline earth elements are reviewed. The determination of the evaporation thermodynamical quantities and the enthalpy of formation of CaTe, SrTe, BaTe, SmTe, YbTe and TmTe 1,30 is outlined. The measurement and thermodynamical interpretation of the dissociation pressure as well as the determination of standard enthalpy of formation using the Knudsen effusion method are presented. The experimentally obtained enthalpies of formation are compared with thermodynamical data calculated from refined, prediction methods.

Ludwigs, Johannes

338

Concentrations of inorganic elements in biomass fuels and recovery in the different ash fractions  

Microsoft Academic Search

Inorganic elements and compounds in biomass fuels influence the combustion process and the composition of the ashes produced. Consequently, knowledge about the material fluxes of inorganic elements and compounds during biomass combustion for different kinds of biofuels and their influencing variables is of great importance. The results gained will especially influence the future design and control of biomass furnaces and

Ingwald Obernberger; Friedrich Biedermann; Walter Widmann; Rudolf Riedl

1997-01-01

339

The Distribution Characteristics of Elemental Components between Fine and Coarse Particle Fractions in Chongju, Korea  

Microsoft Academic Search

The distribution characteristics of airborne particulate matter (PM) were investigated in terms of the relationships between different constitu- ents (elements) and between different particle ranges (fine vs. coarse) from the city of Chongju, South Korea for approximately a year (October 1995 to August 1996). For the purpose of our study, the elemental compositions of both fine (FP: PM 2.5) and

Hak Sung Lee; Byung-Wook Kang; Ki-Hyun Kim

2005-01-01

340

Rare earth elements in the sedimentary cycle - A pilot study of the first leg  

NASA Technical Reports Server (NTRS)

The effects of source rock composition and climate on the natural abundances of rare elements (REE) in the first leg of the sedimentary cycle are evaluated using a study with Holocene fluvia sands. The medium grained sand fraction of samples collected from first order streams exclusively draining granitic plutons in Montana (semi-arid), Georgia (humid), and South Carolina (humid) are analyzed. It is found that the REE distribution patterns (but not the total absolute abundances) of the daughter sands are very similar, despite compositional differences between parent plutons. Averages of the three areas are determined to have a La/Lu ratio of about 103, showing a depletion of heavy REE with respect to an average granite (La/Lu = 79) or the composition of North American Shales (La/Lu = 55). However, the Eu/Sm ratio in sands from these areas is about 0.22, which is very close to this ratio in North American Shales (0.21), although the overall REE distribution of these sands is not similar to that of the North American Shales in any way. It is concluded that the major rock type, but neither its minor subdivisions nor the climate, controls the REE distribution patterns in first cycle daughter sands, although the total and the parent rock-normalized abundances of REE in sands from humid areas are much lower than those in sands from arid areas.

Basu, A.; Blanchard, D. P.; Brannon, J. C.

1982-01-01

341

Trace elements and REE fractionation in subsoils developed on sedimentary and volcanic rocks: case study of the Mt. Vulture area, southern Italy  

NASA Astrophysics Data System (ADS)

There is an increasing interest in the distribution of rare earth elements (REEs) within soils, primarily as these elements can be used to identify pedogenetic processes and because soils may be future sources for REE extraction, despite much attention should be paid to the protection and preservation of present soils. Here, we evaluate the processes that control the distribution of REEs in subsoil horizons developed over differing lithologies in an area of low anthropogenic contamination, allowing estimates of the importance of source rocks and weathering. Specifically, this study presents new data on the distribution of REEs and other trace elements, including transition and high-field-strength elements, in subsoils developed on both Quaternary silica-undersaturated volcanic rocks and Pliocene siliciclastic sedimentary rocks within the Mt. Vulture area of the southern Apennines in Italy. The subsoils in the Mt. Vulture area formed during moderate weathering (as classified using the chemical index of alteration) and contain an assemblage of secondary minerals that is dominated by trioctahedral illite with minor vermiculite. The REEs, high-field-strength elements, and transition metals have higher abundances in subsoils that developed from volcanic rocks, and pedogenesis caused the Mt. Vulture subsoils to have REE concentrations that are an order of magnitude higher than typical values for the upper continental crust. This result indicates that the distribution of REEs in soils is a valuable tool for mineral exploration. A statistical analysis of inter-elemental relationships indicates that REEs are concentrated in clay-rich fractions that also contain significant amounts of low-solubility elements such as Zr and Th, regardless of the parent rock. This suggests that low-solubility refractory minerals, such as zircon, play a significant role in controlling the distribution of REEs in soils. The values of (La/Yb)N and (Gd/Yb)N fractionation indices are dependent on the intensity of pedogenesis; soils in the study area have values that are higher than typical upper continental crust ratios, suggesting that soils, especially those that formed during interaction with near neutral to acidic organic-rich surface waters, may represent an important source of both light REEs and medium REEs (MREEs). In comparison, MREE/heavy REE fractionation in soils that form during moderate weathering may be affected by variations in parent rock lithologies, primarily as MREE-hosting minerals, such as pyroxenes, may control (La/Sm)N index values. Eu anomalies are thought to be the most effective provenance index for sediments, although the anomalies within the soils studied here are not related to the alteration of primary minerals, including feldspars, to clay phases. In some cases, Eu/Eu* values may have a weak correlation with elements hosted by heavy minerals, such as Zr; this indicates that the influence of mechanical sorting of clastic particles during sedimentary transport on the Eu/Eu* values of siliciclastic sediments needs to be considered carefully.

Mongelli, Giovanni; Paternoster, Michele; Rizzo, Giovanna; Sinisi, Rosa

2014-06-01

342

Trace elements and REE fractionation in subsoils developed on sedimentary and volcanic rocks: case study of the Mt. Vulture area, southern Italy  

NASA Astrophysics Data System (ADS)

There is an increasing interest in the distribution of rare earth elements (REEs) within soils, primarily as these elements can be used to identify pedogenetic processes and because soils may be future sources for REE extraction, despite much attention should be paid to the protection and preservation of present soils. Here, we evaluate the processes that control the distribution of REEs in subsoil horizons developed over differing lithologies in an area of low anthropogenic contamination, allowing estimates of the importance of source rocks and weathering. Specifically, this study presents new data on the distribution of REEs and other trace elements, including transition and high-field-strength elements, in subsoils developed on both Quaternary silica-undersaturated volcanic rocks and Pliocene siliciclastic sedimentary rocks within the Mt. Vulture area of the southern Apennines in Italy. The subsoils in the Mt. Vulture area formed during moderate weathering (as classified using the chemical index of alteration) and contain an assemblage of secondary minerals that is dominated by trioctahedral illite with minor vermiculite. The REEs, high-field-strength elements, and transition metals have higher abundances in subsoils that developed from volcanic rocks, and pedogenesis caused the Mt. Vulture subsoils to have REE concentrations that are an order of magnitude higher than typical values for the upper continental crust. This result indicates that the distribution of REEs in soils is a valuable tool for mineral exploration. A statistical analysis of inter-elemental relationships indicates that REEs are concentrated in clay-rich fractions that also contain significant amounts of low-solubility elements such as Zr and Th, regardless of the parent rock. This suggests that low-solubility refractory minerals, such as zircon, play a significant role in controlling the distribution of REEs in soils. The values of (La/Yb)N and (Gd/Yb)N fractionation indices are dependent on the intensity of pedogenesis; soils in the study area have values that are higher than typical upper continental crust ratios, suggesting that soils, especially those that formed during interaction with near neutral to acidic organic-rich surface waters, may represent an important source of both light REEs and medium REEs (MREEs). In comparison, MREE/heavy REE fractionation in soils that form during moderate weathering may be affected by variations in parent rock lithologies, primarily as MREE-hosting minerals, such as pyroxenes, may control (La/Sm)N index values. Eu anomalies are thought to be the most effective provenance index for sediments, although the anomalies within the soils studied here are not related to the alteration of primary minerals, including feldspars, to clay phases. In some cases, Eu/Eu* values may have a weak correlation with elements hosted by heavy minerals, such as Zr; this indicates that the influence of mechanical sorting of clastic particles during sedimentary transport on the Eu/Eu* values of siliciclastic sediments needs to be considered carefully.

Mongelli, Giovanni; Paternoster, Michele; Rizzo, Giovanna; Sinisi, Rosa

2014-02-01

343

The Use of Lead Isotope and Rare Earth Element Geochemistry for Forensic Geographic Provenancing  

NASA Astrophysics Data System (ADS)

Lead isotope and rare earth element composition of modern human bones are analyzed to explore their utility for geographical provenancing. DNA analysis is the standard for identification of individuals. DNA analysis requires a DNA match for comparison. Thus, DNA analysis is of limited use in cases involving unknown remains. Trace elements are incorporated into bones and teeth during biomineralization, recording the characteristics of an individual's geochemical environment. Teeth form during adolescence, recording the geochemical environment of an individual's youth. Bones remodel throughout an individual's lifetime. Bones consist of two types of bone tissue (cortical and trabecular) that remodel at different rates, recording the geochemical environment at the time of biomineralization. Cortical bone tissue, forming the outer surface of bones, is dense, hard tissue that remodels in 25-30 yrs. Conversely, trabecular bone tissue, the inner cavity of bones, is low density, porous and remodels in 2-5 years. Thus, analyzing teeth and both bone tissues allows for the development of a geographical time line capable of tracking immigration patterns through time instead of only an individual's youth. Geochemical isotopic techniques (Sr, O, C, N) have been used for geographical provenancing in physical anthropology. The isotopic values of Sr, C, O, N are predominantly a function of soil compositions in areas where food is grown or water is consumed. Application of these provenancing techniques has become difficult as an individual's diet may reflect the isotopic composition of foods obtained at the local grocer as opposed to local soil compositions. Thus, we explore the use of REEs and Pb isotopes for geographical provenancing. Pb and REEs are likely more reliable indicators of modern geographical location as their composition are high in bio-available sources such as local soils, atmospheric aerosols, and dust as opposed to Sr, C, O, N that are controlled by food and drinking water. Lead isotope and REE analysis of trabecular and cortical bone tissue of 60 femoral heads resected during hip replacement surgery at the Univ. of Roch. Medical Center were analyzed by a combination of TIMS and ICP-MS. Results show that Pb compositions are consistent with local soil with variable inputs from known environmental sources. Several samples demonstrate inputs from known environmental sources (e.g. Mississippi Valley ore) that was used in paint, solder, and US gasoline. Additionally, results suggest bioincorporation of Pb with isotopic composition consistent with that observed for Canadian gasoline aerosols. Immigrants included in the study show Pb compositions distinctly different than local residents.

Carey, A.; Darrah, T.; Harrold, Z.; Prutsman-Pfeiffer, J.; Poreda, R.

2008-12-01

344

Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems  

SciTech Connect

Rare earth element (REE) and yttrium (Y) concentrations were measured in fluids collected from deep-sea hydrothermal systems including the Mid-Atlantic Ridge (MAR), i.e., Menez Gwen, Lucky Strike, TAG, and Snakepit; the East Pacific Rise (EPR), i.e., 13{degree}N and 17--19{degree}S; and the Lau (Vai Lili) and Manus (Vienna Woods, PacManus, Desmos) Back-arc Basins (BAB) in the South-West Pacific. In most fluids, Y is trivalent and behaves like Ho. Chondrite normalized Y-REE (Y-REE{sub N}) concentrations of fluids from MAR, EPR, and two BAB sites, i.e., Vai Lili and Vienna Woods, showed common patterns with LREE enrichment and positive Eu anomalies. REE analysis of plagioclase collected at Lucky Strike strengthens the idea that fluid REE contents, are controlled by plagioclase phenocrysts. Other processes, however, such as REE complexation by ligands (Cl{sup {minus}}, F{sup {minus}}, So{sub 4}{sup 2{minus}}), secondary phase precipitation, and phase separation modify REE distributions in deep-sea hydrothermal fluids. REE speciation calculations suggest that aqueous REE are mainly complexed by Cl{sup {minus}} ions in hot acidic fluids from deep-sea hydrothermal systems. REE concentrations in the fluid phases are, therefore, influenced by temperature, pH, and duration of rock-fluid interaction. Unusual Y-REE{sub N} patterns found in the PacManus fluids are characterized by depleted LREE and a positive Eu anomaly. The Demos fluid sample shows a flat Y-REE{sub N} pattern, which increases regularly from LREE to HREE with no Eu anomaly. These Manus Basin fluids also have an unusual major element chemistry with relatively high Mg, So{sub 4}, H{sub 2}S, and F contents, which may be due to the incorporation of magmatic fluids into heated seawater during hydrothermal circulation. REE distribution in PacManus fluids may stem from a subseafloor barite precipitation and the REE in Demos fluids are likely influenced by the presence of sulfate ions.

Douville, E. [Univ. Bretagne Occidentale, Brest (France). Dept. de Chimie] [Univ. Bretagne Occidentale, Brest (France). Dept. de Chimie; [IFREMER Centre de Brest, Plouzane (France); Appriou, P. [Univ. Bretagne Occidentale, Brest (France)] [Univ. Bretagne Occidentale, Brest (France); Bienvenu, P. [CEA Cadarache, Saint Paul Lez Durance (France). Lab. d`Analyses Radiochimiques et Chimiques] [CEA Cadarache, Saint Paul Lez Durance (France). Lab. d`Analyses Radiochimiques et Chimiques; Charlou, J.L.; Donval, J.P.; Fouquet, Y. [IFREMER Centre de Brest, Plouzane (France)] [IFREMER Centre de Brest, Plouzane (France); Gamo, Toshitaka [Univ. of Tokyo, Nakano, Tokyo (Japan). Ocean Research Inst.] [Univ. of Tokyo, Nakano, Tokyo (Japan). Ocean Research Inst.

1999-03-01

345

PQQ-dependent methanol dehydrogenases: rare-earth elements make a difference.  

PubMed

Methanol dehydrogenase (MDH) catalyzes the first step in methanol use by methylotrophic bacteria and the second step in methane conversion by methanotrophs. Gram-negative bacteria possess an MDH with pyrroloquinoline quinone (PQQ) as its catalytic center. This MDH belongs to the broad class of eight-bladed ? propeller quinoproteins, which comprise a range of other alcohol and aldehyde dehydrogenases. A well-investigated MDH is the heterotetrameric MxaFI-MDH, which is composed of two large catalytic subunits (MxaF) and two small subunits (MxaI). MxaFI-MDHs bind calcium as a cofactor that assists PQQ in catalysis. Genomic analyses indicated the existence of another MDH distantly related to the MxaFI-MDHs. Recently, several of these so-called XoxF-MDHs have been isolated. XoxF-MDHs described thus far are homodimeric proteins lacking the small subunit and possess a rare-earth element (REE) instead of calcium. The presence of such REE may confer XoxF-MDHs a superior catalytic efficiency. Moreover, XoxF-MDHs are able to oxidize methanol to formate, rather than to formaldehyde as MxaFI-MDHs do. While structures of MxaFI- and XoxF-MDH are conserved, also regarding the binding of PQQ, the accommodation of a REE requires the presence of a specific aspartate residue near the catalytic site. XoxF-MDHs containing such REE-binding motif are abundantly present in genomes of methylotrophic and methanotrophic microorganisms and also in organisms that hitherto are not known for such lifestyle. Moreover, sequence analyses suggest that XoxF-MDHs represent only a small part of putative REE-containing quinoproteins, together covering an unexploited potential of metabolic functions. PMID:24816778

Keltjens, Jan T; Pol, Arjan; Reimann, Joachim; Op den Camp, Huub J M

2014-07-01

346

Biogeochemical implications from dissolved rare earth element and Nd isotope distributions in the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

Dissolved rare earth element (REE) concentrations and Nd isotope compositions were measured for surface waters and full water column profiles of the Gulf of Alaska (GoA), and compared to water mass properties and circulation in order to better understand the mechanisms controlling the input and transport of REEs in the ocean. The REEs display a typical open-ocean range of concentrations (i.e., La: 12-66 pM; Lu: 0.2-2.5 pM) and depth distributions (i.e., surface ocean depletion and enrichment with water depth). Nd isotope signatures are highly radiogenic, as expected for the North Pacific margin (ranging from -3.8 to +0.2 ?Nd). The most radiogenic values were found in the coastal waters but also in the cores of eddies, indicating efficient export of REEs from the margins and across the mixed layer. This is the first time that distinct Nd isotope distributions in near surface waters can be directly assigned to offshore eddy transport. A distinct mid-depth (˜2200 m) Nd isotope signal was found that most likely reflects advection of a water mass that formed through past down-welling in the Northern Pacific. Subsurface Nd isotope compositions appear to behave conservatively and can be explained through a REE distribution model proposed here. This model is based on multivariate analysis of the REEs and invokes two distinct “pools” of dissolved REEs: a “passive pool” complexed by carbonate ions, and a “bio-reactive pool” that is microbially manipulated. The latter “pool” is only significant in the upper water column and most likely reflects the indirect effects of microbial cycling of iron. Our model of the open ocean REE distribution contributes to explaining the conservative nature of Nd isotopes and provides a mechanism linking surface ocean and pore water REE dynamics.

Haley, Brian A.; Frank, Martin; Hathorne, Ed; Pisias, Nick

2014-02-01

347

Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean  

NASA Astrophysics Data System (ADS)

The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (<12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE (?REE) concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water ?REE concentrations were measured close to the sediment-water interface at ~2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in ?REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.

Himmler, Tobias; Haley, Brian A.; Torres, Marta E.; Klinkhammer, Gary P.; Bohrmann, Gerhard; Peckmann, Jörn

2013-07-01

348

Preparation of rare-earth element doped Mg2Si by FAPAS  

NASA Astrophysics Data System (ADS)

Rare-earth elements (Re) Sc and Y doped Mg2Si thermoelectric materials were made via a field-activated and pressure-assisted synthesis (FAPAS) method at 1023-1073 K, 50 MPa for 15 min. The samples created using this method have uniform and compact structures. The average grain size was about 1.5-2 ?m, the micro-content of Re did not change the matrix morphology. The sample with 2500 ppm Sc obtained the best See-beck coefficient absolute value, about 1.93 times of that belonging to non-doped Mg2 Si at about 408 K. The electric conductivity of the sample doped with 2000 ppm Y becomes 1.69 times of that of pure Mg2Si at 468 K, while the former had a better comprehensive electrical performance. Their thermal conductivity was reduced to 70% and 84% of that of non-doped Mg2Si. Thus, the figure of merit and ZT of these two samples were enhanced visibly, which were 3.3 and 2.4 times of the non-doped samples at 408 K and 468 K, respectively. The maximal ZT belonging to samples doped with 2500 ppm Sc went up to 0.42 at about 498 K, higher than 0.40 of sample doped with 2000 ppm Y at 528 K and 0.25 of non-doped Mg2Si at 678 K, and the samples doped with Sc seemed to get the best thermoelectric performances at lower temperature.

Liqi, Wang; Qingsen, Meng; Wenhao, Fan

2012-11-01

349

Recovery and separation of rare earth elements using columns loaded with DNA-filter hybrid.  

PubMed

Given that the supply of several rare earth elements (REEs) is sometimes limited, recycling REEs used in various advanced materials, such as Nd magnets, is important for realizing efficient use of REE resources. In the present work, the feasibility of using DNA for REE recovery and separation was examined, along with the identification of the binding site of REEs in DNA. In particular, a DNA-cellulose filter paper hybrid was prepared so that DNA-based materials can be used for the separation of REEs using columns loaded with DNA. N,N'-Disuccinimidyl was used as a cross-linker reagent for the fixation of DNA onto a fibrous cellulose filter. The results showed that (i) the DNA-filter hybrid has a sufficiently high affinity to adsorb REEs; (ii) the adsorption capacity was 0.182 mg/g for Nd; and (iii) the affinity of REEs for DNA was stronger for REEs with larger atomic numbers. The difference of the affinity among REEs in the third result was compared with the adsorption patterns of REEs discussed in the literature. The comparison suggests that phosphate in the DNA-filter paper hybrid was responsible for REE adsorption onto the hybrid. The results were supported by the Nd, Dy, and Lu L(III)-edge EXAFS; the REE-P shell was identified for the second neighboring atom, showing the importance of the phosphate site as REE binding sites. The difference in the affinity among REEs suggest that group separation of REEs (such as La, Ce, (Pr and Nd), (Ho, Dy, and Er), (Tb and Gd), (Sm, Eu), Tm, Yb, and Lu) is possible, although complete isolation of each REE from a solution containing all REEs may be difficult. For practical applications, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste using columns loaded with the DNA-filter hybrid. PMID:23059995

Takahashi, Yoshio; Kondo, Kazuhiro; Miyaji, Asami; Umeo, Miyuki; Honma, Tetsuo; Asaoka, Satoshi

2012-01-01

350

Aluminium competitive effect on rare earth elements binding to humic acid  

NASA Astrophysics Data System (ADS)

Competitive mechanisms between rare earth elements (REE) and aluminium for humic acid (HA) binding were investigated by combining laboratory experiments and modeling to evaluate the effect of Al on REE-HA complexation. Results indicates that Al3+ competes more efficiently with heavy REE (HREE) than with light REE (LREE) in acidic (pH = 3) and low REE/HA concentration ratio conditions providing evidence for the Al high affinity for the few HA multidentate sites. Under higher pH - 5 to 6 - and high REE/HA conditions, Al is more competitive for LREE suggesting that Al is bound to HA carboxylic rather than phenolic sites. PHREEQC/Model VI Al-HA binding parameters were optimized to simulate precisely both Al binding to HA and Al competitive effect on REE binding to HA. REE-HA binding pattern is satisfactorily simulated for the whole experimental conditions by the ?LK1A optimization (i.e. ?LK1A controls the distribution width of log K around log KMA). The present study provides fundamental knowledge on Al binding mechanisms to HA. Aluminium competitive effect on other cations binding to HA depends clearly on its affinity for carboxylic, phenolic or chelate ligands, which is pH dependent. Under circumneutral pH such as in natural waters, Al should lead to LREE-depleted patterns since Al is expected to be bound to weak HA carboxylic groups. As deduced from the behavior of Al species, other potential competitor cations are expected to have their own competitive effect on REE-HA binding. Therefore, in order to reliably understand and model REE-HA patterns in natural waters, a precise knowledge of the exact behavior of the different REE competitor cations is required. Finally, this study highlights the ability of the REE to be used as a "speciation probe" to precisely describe cation interactions with HA as here evidenced for Al.

Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline; Bouhnik-Le Coz, Martine

2012-07-01

351

Rare earth element distributions in anoxic waters of the Cariaco Trench  

NASA Astrophysics Data System (ADS)

The concentrations of dissolved and suspended particulate rare earth elements in the Cariaco Trench are reported. In solution all REE, notably Ce, show a sharp increase just at or below the oxic/anoxic interface at 300 meters depth. Particulate concentrations show a complementary decrease at the same depth. The overlying oxic waters exhibit a negative Ce anomaly; the anoxic waters carry a slightly positive Ce anomaly. The particulate Ce anomaly reaches a maximum just above the interface, coinciding with maxima for particulate Mn and Fe and minima for the dissolved Ce anomaly and dissolved Ce, Mn and Fe. Thermodynamic calculations predict that the solubility of Ce(IV)O 2 is greatly enhanced by the steep p?-drop at the O 2/H 2S interface whereas oxygenated seawater is grossly oversaturated with dissolved Ce(III). However, the dramatic shifts in pe and absolute total Ce concentration do not affect the relative speciation of Ce in solution, which varies only with pH and not with p? because dissolved Ce(IV)-species are negligible. The cycling of Ce across the oxic/anoxic boundary is driven largely by its own redox chemistry as with Fe and Mn. The remaining REE, being strictly trivalent, are recycled in association with the dissolution-precipitation of (ferro)manganese oxyhydroxides. The relative turnover rates at the interface are ranked as Mn > Ce = Ce-anomaly > Nd, Sm, Eu, La, Dy, Er. The observed absence of Eu anomalies would render in situ reduction of Eu(III) to Eu(II) unlikely; thermodynamic considerations also rule out the existence of Eu(II) species in low temperature reducing environments.

de Baar, Hein J. W.; German, Christopher R.; Elderfield, Henry; van Gaans, Pauline

1988-05-01

352

Significant Li isotope fractionation in geochemically evolved rare element-bearing pegmatites from the Little Nahanni Pegmatite Group, NWT, Canada  

NASA Astrophysics Data System (ADS)

Lithium isotope signatures of whole rock pegmatite samples and mineral separates from the rare element-bearing Little Nahanni Pegmatite Group, NWT, and whole rock samples from nearby granitic intrusions were measured. Correlation of the Li isotopic values from the pegmatite dikes with whole rock trace element geochemistry, mineralogy and primary textural evidence reflect mechanisms of Li isotopic fractionation during pegmatite formation. The heavier ? 7Li signatures within the broad range measured from whole rock LNPG samples (- 0.94‰ to + 11.36‰) are related to the consolidation of the final ~ 15% melt fraction of a volatile-rich peraluminous magma in the late stages of magmatic fractionation. Rock-forming minerals (quartz, albite, spodumene and mica) display ? 7Li signatures that indicate consolidation of the dikes under variable, non-equilibrium conditions. Lithium isotope signatures of relatively cool, highly evolved peraluminous magmas reflect the build-up of fluxes (e.g., H 2O and F) and provide a qualitative assessment of the state of mineral/melt chemical equilibrium.

Barnes, Elspeth M.; Weis, Dominique; Groat, Lee A.

2012-02-01

353

Rare earth distributions in clay minerals and in the clay-sized fraction of the Lower Permian Havensville and Eskridge shales of Kansas and Oklahoma  

Microsoft Academic Search

The REE (rare earth element) content of a wide variety of clay mineral groups have been analyzed using radiochemical neutron activation and have been found to be quite variable in absolute REE content (range of REE = 5.4-1732) and less variable in relative REE content (range of chondritenormalized La \\/ Lu = 0.9-16.5). The variable REE content of the clay

Robert L. Cullers; Sambhudas Chaudhuri; Bill Arnold; Moon Lee; Carlton W. Wolf Jr.

1975-01-01

354

Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH  

Microsoft Academic Search

Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave

Christopher H. Gammons; Scott A. Wood; David A. Nimick

2005-01-01

355

Rare-earth element geochemistry of Colour Lake, an acidic freshwater lake on Axel Heiberg Island, Northwest Territories, Canada  

Microsoft Academic Search

A lake column profile was collected in 24 m of water from Colour Lake, Axel Heiberg Island, Northwest Territories, Canada, in early June of 1991 beneath 1.8 m of lake-ice. The rare-earth element (REE) concentrations of the acidic, fresh waters of Colour Lake were analyzed, along with the major solute chemistry, in order to investigate REE distribution and speciation in

Kevin H. Johannesson; W. Berry Lyons

1995-01-01

356

Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa  

Microsoft Academic Search

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The 87Sr\\/86Sr ratios of the chimneys indicate that they have precipitated from

J. A. Barrat; J. Boulègue; J. J. Tiercelin; M. Lesourd

2000-01-01

357

Production oriented method for the determination of rare earth and other trace elements in rocks by ICP-MS  

Microsoft Academic Search

The rare earth elements along with Y, Sc, Co, Hf, Nb, Rb, Ta, Th, Ti, U, V and Zr have been determined in ten standard reference materials and ten granitoid samples by inductively coupled plasma mass spectrometry (ICP-MS). Two digestion methods have been used: (a) dissolution with hydrofluoric-perchloric acid followed by fusion of the residue with lithium metaborate, (b) dissolution with hydrofluoric

I. Rautiainen; M.-L. Hagel-Brunnström; L. Heiskanen; E. Kallio

1996-01-01

358

Rare earth element and clay minerals of paddy soils from the central region of the Mekong River, Laos  

Microsoft Academic Search

The rare earth elements (REE) content, particle-size distribution, and clay mineralogical composition were analyzed for the paddy soils collected from the central region of the Mekong River, Laos, to study the origin and inherent potentiality of soils. REE as the chondrite-normalized curve of the plot of Ce\\/Eu against Eu\\/Sm were found to be useful for grouping soils according to their

K. Egashira; K. Fujii; S. Yamasaki; P. Virakornphanich

1997-01-01

359

The geochemistry of rare earth elements in the seasonally anoxic water column and porewaters of Chesapeake Bay  

Microsoft Academic Search

A twelve cruise time-series study of a seasonally anoxic basin in Chesapeake Bay was carried out between February 1988 and February 1989. Data from filtered bottom water and upper (0-1 cm) porewater samples are presented. This is the first study in which time-series measurements have been employed to understand the low temperature geochemistry of rare earth elements (REEs). The focus

E. R. Sholkovitz; T. J. Shaw; D. L. Schneider

1992-01-01

360

Rare-earth element geochemistry of banded iron formations and associated amphibolite from the Sargur belts, south India  

Microsoft Academic Search

Major and rare-earth elements (REE) of banded iron formations (BIFs) and associated amphibolite from the Sargur belts, the oldest schist belts in the Dharwar craton, were determined by X-ray fluorescence and inductively coupled plasma mass spectrometry (ICP-MS). The chondrite-normalized REE patterns of BIFs are light REE-enriched with a striking positive Eu anomaly, resembling those of modern hydrothermal solutions from the

Yasuhiro Kato; Takanori Kawakami; Takashi Kano; Keitaro Kunugiza; N. S. Swamy

1996-01-01

361

Biological effect of rare-earth elements on anti-oxidation enzymes in wheat under acid rain stress  

Microsoft Academic Search

Based on pot-culture experiments, the biological effect of rare-earth elements (REE) on antioxidation enzymes of wheat under\\u000a acid rain stress was studied. The results show that both acid rain and REE can affect the activity of anti-oxidation enzymes\\u000a of wheat to different extents. Under the acid rain stress, anti-oxidation enzymes (CAT, SOD) of wheat showed single peak curve\\u000a with the

Chongling Yan; Yetang Hong; Xianke Yang; Shunzhen Fu; Shanyi Wu

1999-01-01

362

Calculations of giant magnetoelectric effect in multiferroic composites of rare-earth-iron alloys and PZT by finite element method  

Microsoft Academic Search

Magnetoelectric effect of laminated composites of rare-earth-iron alloys (Terfenol-D) and lead–zirconate–titanate (PZT) is calculated by using finite element method. The dependences of the magnetoelectric response on the geometric configuration, the orientations of magnetostriction and polarization, and the applied magnetic field are presented for various sandwiched composites in details. The giant magnetoelectric effect predicted for the Terfenol-D\\/PZT composites is in agreement

Gang Liu; Ce-Wen Nan; Ning Cai; Yuanhua Lin

2004-01-01

363

Hf and Nd Isotope Evidence for Production of an Incompatible Trace Element Enriched Crustal Reservoir in Early Earth (Invited)  

NASA Astrophysics Data System (ADS)

The final significant stage of accretion of the Earth was likely a collision between proto-Earth and a Mars sized impactor that formed the Moon. This event is thought to have produced enough thermal energy to melt all or most of the Earth, with a consequent magma ocean (MO). During subsequent cooling, the Earth would have formed its protocrust and corresponding mantle lithosphere, consisting of solidified basalt-komatiitic melt, in combination with buoyant cumulates and late stage residual melts from the MO. Relative to the convecting mantle, portions of this protolithosphere are likely to have been enriched in incompatible trace elements (ITE) in sufficient quantities to contain a significant amount of the bulk Earth’s budget for rare earth elements, U, Th, and Hf. If the protolithosphere was negatively buoyant, it may have overturned at or near the final stages of MO crystallization and a significant portion of that material may have been transported into the deep mantle where it resided and remixed into the convecting mantle over Earth history [1,2]. If the protolithosphere remained positively buoyant, its crust would have likely begun to erode from surface processes, and subsequently recycled back into the mantle over time as sediment and altered crust, once a subduction mechanism arose. The Nd and Hf isotopic compositions of Earth’s earliest rocks support the idea that an early-formed ITE-enriched reservoir was produced. The maxima in 142Nd/144Nd for 3.85 to 3.64 Ga rocks from Isua, Greenland decreases from +20 ppm to +12 ppm relative to the present day mantle value, respectively [3]. This indicates mixing of an early-formed ITE enriched reservoir back into the convecting mantle. In addition, zircons from the 3.1 Ga Jack Hills conglomerate indicate that material with an enriched 176Lu/177Hf of ~0.02 and an age of 4.4 Ga or greater was present at the Earth’s surface over the first 2 Ga of Earth history, supporting the scenario of a positively buoyant, early-formed ITE-enriched reservoir [4]. This early-formed enriched ITE reservoir is indistinguishable in age and 176Lu/177Hf to those that formed in the Moon and Mars [5,6]. Hence all three terrestrial bodies must have undergone similar early differentiation and each formed and sustained their requisite early-formed ITE-enriched reservoirs at or near their surfaces. For all three terrestrial bodies, their early-formed ITE-enriched reservoirs appear to be the result of solidification of late stage residual liquids from their respective MO’s at or prior to 4.4 Ga. In Earth, mixing of an early-formed ITE-enriched reservoir back into the mantle likely occurred back into the convecting mantle at or before 3.9 Ga. For the Moon and Mars, the lack of plate tectonics preserved their early-formed ITE-enriched lithospheric reservoirs. [1] Tolstikhin and Hofmann, PEPI (2005) 148, 109. [2] Boyet and Carlson, Science (2005) 309, 576. [3] Bennett et al., Science (2007) 218, 1907. [3] Kemp et al., EPSL (2010) 296, 45. [5] Taylor et al. (2009) 279, 157. [6] Lapen et al., Science (2010) 328, 347.

Brandon, A. D.; Debaille, V.; Lapen, T. J.

2010-12-01

364

Geochemical fractionation of trace elements in sediments of Hugli River (Ganges) and Sundarban wetland (West Bengal, India).  

PubMed

A sequential extraction procedure was carried out to determinate the concentrations of 11 elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in different geochemical phases of sediments collected along the Hugli (Ganges) River Estuary and in the Sundarban mangrove wetland, eastern coastal part of India. The chemical speciation of elements was determined using the three-step sequential extraction procedure described by the European Community Bureau of Reference. Total metal concentration was determined using a microwave-assisted acid digestion procedure. Metal concentrations were near the background level except for As for which a moderate pollution can be hypothesized. The mobility order of the metals was: Cd?>?Mn?>?Cu?>?Zn?>?As?>?Co?>?Pb?>?Ni?>?Fe?>?Cr?>?Al. The highest percentage of Cd (>60%) was found in the most labile phase. Residual fraction was prevailing for Fe, Cr and Al, while Pb was mainly associated with the reducible fraction. Data were compared with Sediment Quality Guidelines to estimate the relationship between element concentrations and adverse biological effects on benthic community, finding the possibility of some toxic effects due to the presence of As in the entire studied area and Cd, only in Calcutta. PMID:22270595

Massolo, Serena; Bignasca, Antonello; Sarkar, Santosh Kumar; Chatterjee, Mousumi; Bhattacharya, Bhaskar Deb; Alam, Aftab

2012-12-01

365

Fractionation of High Field Strength Elements During Water-Saturated Partial Melting of Eclogite: Can Subduction Produce a Mantle Reservoir With Superchondritic Nb/Ta ?  

NASA Astrophysics Data System (ADS)

An examination of the relative abundances of Ti, Zr, Nb and Ta in the depleted mantle and continental crust suggests the existence of an additional reservoir characterized by superchondritic Nb/Ta and Ti/Zr ratios [1]. While it has been shown that rutile-bearing refractory eclogite produced by partial melting of subducted oceanic crust is a potential candidate for this reservoir [2], experimental studies have consistently produced rutile-melt partition coefficients that cannot generate the required high field strength element fractionations [3]. Here I present new experimental results demonstrating that the temperature dependences of rutile-melt partitioning of Ta and Nb differ enough to produce DNb/DTa ~1.4 during H2O-saturated partial melting of eclogite at 3 GPa. Therefore, partial melting of subducted oceanic crust at these conditions is capable of producing rutile-bearing refractory eclogite with superchondritic Nb/Ta. Experiments were carried out on model rhyodacite and haplobasalt base melt compositions in the system SiO2-Al2O3-MgO-CaO-Na2O-K2O. Rutile saturation was achieved by adding 10- 40 wt% TiO2. Each starting composition was doped with ZrO2, Nb2O5, HfO2, and Ta2O5. Low-pressure experiments were carried in a vertical quenching furnace, and high pressure experiments were conducted in a solid-medium piston-cylinder device. The major element compositions of glass and rutile, as well as the trace element content of the rutile, were determined by electron microprobe. The trace element content of the glass was determined SIMS. These experimental results place new constraints on the HFSE fractionations produced by partial melting of subducted oceanic crust. At the low temperatures (~750°C) that characterize the H2O- saturated basalt solidus at 3 GPa [4], partial melting at the amphibolite/eclogite transition will produce a siliceous melt with strong depletions in Ti, Zr, Nb, Hf, and Ta. Further, a Ta/Nb compatibility crossover at 3 GPa and ~1000°C causes these melts to have larger Nb/Ta ratios than the residual eclogite. References: [1] McDonough (1991), Philos Trans R Soc London Ser A, 335:407-418; [2] Rudnick et al. (2000), Science, 287:278-281; [3] Schmidt et al. (2004), Earth Planet Sci Lett, 226:415-432; [4] Lambert and Wyllie (1972), J Geol, 80:693-708.

Gaetani, G. A.

2008-12-01

366

Some data on transuranium element distribution in particle size fractions of Chernobyl soils  

Microsoft Academic Search

Some Chernobyl soils were collected in the north-west direction. The samples have been separated into particle size fractions 1–2; 0.5–1; 0.25–0.5; 0.16–0.25; 0.05–0.16; 0.01–0.05; 0.005–0.01; 0.002–0.005; 0.00005–0.002; and less than 0.00005 mm. The fractions were analyzed on238,239,240Pu,241Am,242,244Cm content. In contrast to the global plutonium fallout, the peak of plutonium activity falls in the particle size range of 0.01–0.05 or 0.005–0.01

V. I. Berezhnoi; N. K. Valetova; G. E. Dunaev; N. A. Kazakov; V. G. Zubarev

1991-01-01

367

Element fractionation in soil from urban-industrialized areas using sequential extraction  

Microsoft Academic Search

Background Goal and Scope  The application of solid-liquid extraction is proposed to assess extractable fractions of components in soil. The application\\u000a of a several step scheme could give a lot of information about mobility of metals associated with specific solid phases, especially\\u000a after separation of top and bottom layers of studied soil. In this study, it was aimed to take into

Beata Krasnod?bska-Ostr?ga; Hendrik Emons; Jerzy Golimowski

2004-01-01

368

APPLICATION OF MECHANICAL ACTIVATION TO PRODUCTION OF PYROCHLORE CERAMIC CONTAINING SIMULATED RARE-EARTH ACTINIDE FRACTION OF HLW  

SciTech Connect

Samples of zirconate pyrochlore ceramic (REE)2(Zr,U)2O7 (REE = La-Gd) containing simulated REE-An fraction of HLW were synthesized by two routes: (1) conventional cold compaction of oxide mixtures in pellets under pressure of 200 MPa and sintering of the pellets at 1550 C for 24 hours; and (2) using preliminary mechanical activation of oxide powders in a linear inductive rotator (LIV-0.5E) and a planetary mill - activator with hydrostatic yokes (AGO-2U) for 5 or 10 min. All the samples sintered at 1550 C were monolithic and dense with high mechanical integrity. As follows from X-ray diffraction (XRD) data, the ceramic sample produced without mechanical activation is composed of pyrochlore as major phase but contains also minor unreacted oxides. The samples prepared from pre-activated mixtures are composed of the pyrochlore structure phase only. Scanning electron microscopy (SEM) data also show higher structural and compositional homogeneity of the samples prepared from mechanically activated batches. The samples produced from oxide mixtures mechanically activated in the LIV for 10 min were slightly contaminated with iron resulting in formation of minor perovskite structure phase not detected by XRD but seen on SEM-images of the samples. Comparison of the samples prepared from non-activated and activated batches showed higher density, lower open porosity, water uptake, and elemental leaching for the samples fabricated from mechanically activated oxide mixtures.

Stefanovsky, S.V.; Kirjanova, O.I.; Chizhevskaya, S.V.; Yudintsev, S.V.; Nikonov, B.S.

2003-02-27

369

Determination of rare earth elements, uranium and thorium in geological samples by ICP-MS, using an automatic fusion machine as an alkaline digestion tool.  

NASA Astrophysics Data System (ADS)

At the present time, rare earth elements deposits have became in strategic resources for extraction of raw materials in order to manufacture high tech devices (computers, LCD, cell phones, batteries for hybrid vehicles, fiber optics and wind turbines) (1).The appropriate analytical determination of the REE ( rare earth elements) in sediment and rock samples , is important to find potential deposits and to recognize geological environments for identifying possible alterations and mineral occurrences. The alkaline fusion, which aim is to move the entire sample from solid to liquid state by forming water soluble complexes of boron and lithium, as a previous procedure for the determination of these elements, usually takes a lot of time due to the complexity of the analysis phase and by the addition of other reagents (Tm and HF ) (2) to compensate the lack of strict temperature control. The objective of this work is to develop an efficient alternative to alkaline digestion using an electrical fusion machine, which allows to create temperature programs with advanced process control and supports up to 5 samples simultaneously, which generates a reproducibility of the method and results during the melting step. Additionally, this new method permits the processing of a larger number of samples in a shorter time. The samples analyzed in this method were weighed into porcelain crucibles and subjected to calcination for 4 hours at 950 ° C in order to determine the Lost on Ignition (LOI ) , that serves to adjust the analytical results and to preserve the shelf life of the platinum ware. Subsequently, a fraction of the calcined sample was weighed into platinum crucibles and mixed with ultra-pure lithium metaborate ( flux ) 1:4 . The crucible was then placed in the fusion machine, which was programmed to take the sample from room temperature to 950 ° C in five minutes, make a small ramp to 970 ° C maintain that temperature for five minutes and download the melt in a 10 % v / v nitric acid solution . After an incorporation time, a fraction of this sample was then diluted 20 times in ultrapure deionized water ( resistivity greater 18.2 megohms / cm ). The diluted sample was analized in the ICP- MS, which was setted in high sensitivity mode. The results were compared through cross samples (the same samples tested in the laboratory were sent to another international laboratory, which works under accreditation ISO 17025 ) and no major deviations (5%) was obtained by making comparisons between the two laboratories. When comparing the results and evaluated the development of the art, it is concluded that this is an alternative that allows performing samples up to 50 alkaline fusions per day with great accuracy, saving resources and time. References: (1) British Geological Survey, Natural Environment Research Council, , Minerals UK Centre of Sustainable mineral development: Rare Earth Elements, p18-22, 2011 (2) Germain Bayon, Jean Alix Barrat, Joel Etoubleau, Mathieu Benoit ,Claire Bollinger, and Sidonie Revillon: Determination of Rare Earth Elements, Sc, Y, Zr, Ba, Hf and Th in Geological Samples by ICP-MS after Tm Addition and Alkaline Fusion, Geostandards and Geoanalytical Research, vol 33-N1, p51-62, 2008

Granda, Luis; Rivera, Maria; Velasquez, Colon; Barona, Diego; Carpintero, Natalia

2014-05-01

370

PRESSURE DROP AND VOID FRACTION EXPERIMENTS IN SIMULATED PATHFINDER BOILER FUEL ELEMENTS  

Microsoft Academic Search

A heat-transfer research and development program is being carried out in ; support of the Pathfinder boilingwater, integral-superheating reactor. Studies ; were made of the effects of tube-sheet type spacers on the axial pressure profile ; in a simulated fuel element. The effect of boiling on the frictional and spacer ; type pressure losses in a 6-ft long test section

G. Kangas; K. Neusen

1963-01-01

371

Trace element and isotopic variations in a zoned pluton and associated volcanic rocks, Unalaska Island, Alaska: A model for fractionation in the Aleutian calcalkaline suite  

Microsoft Academic Search

Trace elements, including rare earth elements (REE), exhibit systematic variations in plutonic rocks from the Captains Bay pluton which is zoned from a narrow gabbroic rim to a core of quartz monzodiorite and granodiorite. The chemical variations parallel those in the associated Aleutian calcalkaline volcanic suite. Concentrations of Rb, Y, Zr and Ba increase as Sr and Ti decrease with

Michael R. Perfit; Hannes Brueckner; James R. Lawrence; Robert W. Kay

1980-01-01

372

Provenance of KREEP and the exotic component - Elemental and isotopic studies of grain size fractions in lunar soils  

NASA Technical Reports Server (NTRS)

Sieve fraction analyses of lunar soils reveal the presence of a fine-grained exotic component enriched in K, Rb, Sr, Ba, and in radiogenic Sr in all soils. The probable source of this exotic component is the areas of high-surficial radioactivity observed by orbital gamma ray spectrometry, such as those at Fra Mauro and Archimedes. If the exotic component is fine-grained KREEP, the origin and distribution of KREEP fragments in the soils are identified. It is suggested that the exotic component represents trace element enriched material located at some depth in the Imbrium area which was surficially deposited during Imbrium excavation.

Evensen, N. M.; Murthy, V. R.; Coscio, M. R., Jr.

1974-01-01

373

Post-assembly magnetization of rare-earth fractional-slot permanent-magnet machines using a Two-Shot Method  

Microsoft Academic Search

This paper studies the post-assembly magnetization of a fractional-slot brushless rare-earth surface permanent-magnet machine with six rotor poles and nine stator slots. In the paper, the simulation method is discussed and it is illustrated that it is possible to fully magnetize the machine after assembly using two pulses of the winding (“Two-Shot Method”) with a rotation of the rotor between

Min-Fu Hsieh; Yao-Min Lien; D. G. Dorrell

2010-01-01

374

Geochemical Controls on Dissolved Rare Earth Elements in Two Contrasting Fluvial Systems: the Lower Mississippi River and the Loch Vale Watershed  

Microsoft Academic Search

The rare earth elements (REEs) form a unique chemical set wherein the gradual decrease in ionic radius across the series leads to systematic changes in geochemical behavior. The geochemical properties of the REEs make them particularly useful tools for inquiring into processes that mobilize elements during weathering and redistribute elements between particulate and dissolved phases in rivers. In this paper,

A. M. Shiller

2001-01-01

375

Metal loading effect on rare earth element binding to humic acid: Experimental and modelling evidence  

NASA Astrophysics Data System (ADS)

The effect of metal loading on the binding of rare earth elements (REE) to humic acid (HA) was studied by combining ultrafiltration and Inductively Coupled Plasma Mass Spectrometry techniques. REE-HA complexation experiments were performed at pH 3 for REE/C molar ratios ranging from ca 4 × 10 -4 to 2.7 × 10 -2. Results show that the relative amount of REE bound to HA strongly increases with decreasing REE/C. A middle-REE (MREE) downward concavity is shown by patterns at high metal loading, whereas patterns at low metal loading display a regular increase from La to Lu. Humic Ion Model VI modelling are close to the experimental data variations, provided that (i) the ?LK 2 parameter (i.e. the Model VI parameter taken into account the presence of strong but low density binding sites) is allowed to increase regularly from La to Lu (from 1.1 to 2.1) and (ii) the published log KMA values (i.e. the REE-HA binding constants specific to Model VI) are slightly modified, in particular with respect to heavy REE. Modelling approach provided evidence that logKdREE patterns with varying REE/C likely arises because REE binding to HA occurs through two types of binding sites in different density: (i) a few strong sites that preferentially complex the heavy REE and thus control the logKdREE atterns at low REE/C; (ii) a larger amount of weaker binding sites that preferentially complex the middle-REE and thus control the logKdREE pattern at high REE/C. Hence, metal loading exerts a major effect on HA-mediated REE binding, which could explain the diversity of published conditional constants for REE binding with HA. A literature survey suggests that the few strong sites activated at low REE/C could be multidentate carboxylic sites, or perhaps N-, or P-functional groups. Finally, an examination of the literature field data proposed that the described loading effect could account for much of the variation in REE patterns observed in natural organic-rich waters (DOC > 5 mg L -1 and 4 ? pH ? 7).

Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

2010-03-01

376

Cerium redox cycles and rare earth elements in the Sargasso Sea  

NASA Astrophysics Data System (ADS)

Two profiles of the rare earth elements (REEs) are reported for the upper water column of the Sargasso Sea. The trivalent-only REEs have remarkably constant concentrations in the upper 500 m of an April 1989 profile and in the upper 200 m of a May 1989 profile. In contrast, Ce concentrations decrease smoothly with increasing depth. In April 1989 Ce decreases from 15.7 pmol/kg at 20 m to 5.1 pmol/kg at 750 m. Cerium, which has Redox transformations in seawater, behaves anomalously with respect to its REE(III) neighbors. While both dissolved Ce and Mn have elevated concentrations in the upper 200 m, their vertical gradients are distinctly different. In contrast to Mn, which reaches a minimum dissolved concentration near the zone (150-250 m) of a particulate Mn maximum, Ce is being removed both near this zone and to depths of at least 750 m. These new profiles indicate that Ce is involved in an upper ocean redox cycle. This interpretation is consistent with the MOFFETT (1990) incubation tracer experiments on the same May 1989 seawater. He showed that Ce (III) oxidation is biologically mediated, probably light inhibited, increases with depth, and 3-4 times slower than Mn(II) oxidation in the 100-200 m zone. "CERoclines" provide new information into the fine scale zonation of redox processes operating in the upper columns of oligothrophic oceans. While the trivalent-only REE have similar concentrations, striking differences exist between our Ce profiles and Ce anomalies and those of DE BAAR et al. (1983) from their August 1980 profile. The increase in their Ce concentration in the upper 150 m is ten times greater than ours. This leads to large positive Ce-anomalies while our samples show well-developed negative anomalies. After reanalyzing archived samples, DE BAAR (1991) has shown that the high Ce concentrations in DE BAAR et al. (1983) are too high due to an unknown analytical cause. His new results agree well with those reported here and rule out a previous interpretation regarding the formation of positive Ce anomalies in the Sargasso Sea.

Sholkovitz, E. R.; Schneider, D. L.

1991-10-01

377

Modeling of rare earth element sorption to the Gram positive Bacillus subtilis bacteria surface.  

PubMed

In this study, rare earth element (REE) binding constants and site concentration on the Gram+ bacteria surfaces were quantified using a multi-site Langmuir isotherm model, along with a linear programming regression method (LPM), applied to fit experimental REE sorption data. This approach found one discrete REE binding site on the Gram+ Bacillus subtilis surface for the pH range of 2.5-4.5. Average log10 REE binding constants for a site j on these bacteria ranged from 1.08±0.04 to 1.40±0.04 for the light REE (LREE: La to Eu), and from 1.36±0.03 to 2.18±0.14 for the heavy REE (HREE: Gd to Lu) at the highest biomass concentration of 1.3 g/L of B. subtilis bacteria. Similar values were obtained for bacteria concentrations of 0.39 and 0.67 g/L indicating the independence of REE sorption constants on biomass concentration. Within the experimental pH range in this study, B. subtilis was shown to have a lower affinity for LREE (e.g. La, Ce, Pr, Nd) and a higher affinity for HREE (e.g. Tm, Yb, Lu) suggesting an enrichment of HREE on the surface of Gram+ bacteria. Total surface binding site concentrations of 6.73±0.06 to 5.67±0.06 and 5.53±0.07 to 4.54±0.03 mol/g of bacteria were observed for LREE and HREE respectively, with the exception of Y, which showed a total site concentration of 9.53±0.03, and a log K(REE,j) of 1.46±0.02 for a biomass content of 1.3 g/L. The difference in these values (e.g. a lower affinity and increased binding site concentration for LREE, and the contrary for the HREE) suggests a distinction between the LREE and HREE binding modes to the Gram+ bacteria reactive surface at low pH. This further implies that HREE may bind more than one monoprotic reactive group on the cell surface. A multisite Langmuir isotherm approach along with the LPM regression method, not requiring prior knowledge of the number or concentration of cell surface REE complexation sites, were able to distinguish between the sorption constant and binding site concentration patterns of LREE and HREE on the Gram+ B. subtilis surface. This approach quantified the enrichment of Tm, Yb and Lu on the bacteria surface and it has therefore proven to be a useful tool for the study of natural reactive sorbent materials controlling REE partitioning in the natural environment. PMID:24183437

Martinez, Raul E; Pourret, Olivier; Takahashi, Yoshio

2014-01-01

378

Rare earth element geochemistry of South Atlantic deep sea sediments: Ce anomaly change at ~54 My  

NASA Astrophysics Data System (ADS)

The geochemistry of the REE (rare earth elements) in oceanic sediments is discussed, based mainly on samples from DSDP Holes 530A and 530B, Leg 75, and Hole 525A, Leg 74. The proposed mechanisms for incorporation of the REE into the marine carbonate phases are adsorption, chiefly onto the carbonate minerals and on Sc, Hf, and Ta-rich Fe-Mn hydroxide flocs as carbonate coatings. The Ce anomaly of marine carbonate was used as an indicator of paleo-ocean water redox conditions: the bottom water of the Angola Basin was in a reducing condition in the Cretaceous. At ca. 54 My, the South Atlantic water condition became oxidizing, similar to the present seawater redox condition. This change was related to the improvement of circulation due to the widening of South Atlantic and the subsidence of water circulation barriers such as the Walvis Ridge and perhaps the Romanche Fracture Zone. The younger (Eocene-Recent) and older (Albian-Santonian) argillaceous sedimentary rocks from 530A (denoted as YSAB and OSAB respectively) show different degrees of Eu depletion with a transition period in between. The REE patterns of OSAB suggest a basaltic origin. The possible sources are Kaoko basalt in Southwest Africa or Namibia and the basaltic Walvis Ridge itself. The decrease in the area covered by Kaoko basalt due to erosion, the subsidence of the Walvis Ridge, and the improvement of water circulation led to changes in the Eu anomaly from Campanian to Paleocene, and resulted in the YSAB REE pattern. Changes in the Sm/Eu, La/Th, Th/Yb, Ti/Al 2O 3, FeO/Al 2O 3, and Hf/Al 2O 3 ratios suggest changes of average source rock composition from and esite to granodiorite. The REE abundances and patterns of younger sediments in the Angola Basin (YSAB) are very similar to those observed in NASC, PAAS, and ES sediments. The YSAB REE abundances and patterns may represent the average REE distribution of the exposed African continental crust. The strong resemblance of REE distributions of YSAB, NASC, PAAS and ES suggests thorough REE mixing from different sources and the uniformity of the average crustal compositions of different continents: Africa, North America, Australia, and Europe

Wang, Y. L.; Liu, Y.-G.; Schmitt, R. A.

1986-07-01

379

Trace element fractionation and transport in boreal rivers and soil porewaters of permafrost-dominated basaltic terrain in Central Siberia  

NASA Astrophysics Data System (ADS)

The chemical status of ˜40 major and trace elements (TE) and organic carbon (OC) in pristine boreal rivers draining the basaltic plateau of Central Siberia (Putorana) and interstitial solutions of permafrost soils was investigated. Water samples were filtered in the field through progressively decreasing pore size (5 ?m ? 0.22 ?m ? 0.025 ?m ? 10 kDa ? 1 kDa) using cascade frontal filtration technique. Most rivers and soil porewaters exhibit 2-5 times higher than the world average concentration of dissolved (i.e., <0.22 ?m) iron (0.03-0.4 mg/L), aluminum (0.03-0.4 mg/L), OC (10-20 mg/L) and various trace elements that are usually considered as immobile in weathering processes (Ti, Zr, Ga, Y, REEs). Ultrafiltration revealed strong relationships between concentration of TE and that of colloidal Fe and Al. According to their partition during filtration and association with colloids, two groups of elements can be distinguished: (i) those weakly dependent on ultrafiltration and that are likely to be present as truly dissolved inorganic species (Li, Na, K, Si, Mn, Mo, Rb, Cs, As, Sb) or, partially (20-30%) associated with small size Fe- and Al-colloids (Ca, Mg, Sr, Ba) and to small (<1-10 kDa) organic complexes (Co, Ni, Cu, Zn), and (ii) elements strongly associated with colloidal iron and aluminum in all ultrafiltrates largely present in 1-100 kDa fraction (Ga, Y, REEs, Pb, V, Cr, Ti, Ge, Zr, Th, U). TE concentrations and partition coefficients did not show any detectable variations between different colloidal fractions for soil porewaters, suprapermafrost flow and surface streams. TE concentration measurements in river suspended particles demonstrated significant contribution (i.e., ?30%) of conventionally dissolved (<0.22 ?m) forms for usually "immobile" elements such as divalent transition metals, Cd, Pb, V, Sn, Y, REEs, Zr, Hf, Th. The Al-normalized accumulation coefficients of TE in vegetation litter compared to basalts achieve 10-100 for B, Mn, Zn, As, Sr, Sn, Sb, and the larch litter degradation is able to provide the major contribution to the annual dissolved flux of most trace elements. It is hypothesized that the decomposition of plant litter in the topsoil horizon leads to Fe(III)-, Al-organic colloids formation and serves as an important source of elements in downward percolating fluids.

Pokrovsky, O. S.; Schott, J.; Dupré, B.

2006-07-01

380

Determination of Rare Earths and Other Trace Elements in Igneous Rocks by Instrumental Activation Analysis.  

National Technical Information Service (NTIS)

An introduction to the use of instrumental activation analysis for geochemical research is provided and the particular significance of rare earth abundances explained. Complete details are given of the experimental techniques used in the instrumental anal...

J. E. Whitley

1974-01-01

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