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1

High field strength element/rare earth element fractionation during partial melting in the presence  

E-print Network

High field strength element/rare earth element fractionation during partial melting in the presence-melt trace element partitioning data for key trace elements (Ti, Hf, Zr, U, Th, Sm, and Yb) is used to compare and contrast the trace element signatures imparted on mantle melts by garnets from peridotitic

van Westrenen, Wim

2

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

3

Diffusive fractionation of trace elements during production and transport of melt in Earth’s upper mantle  

Microsoft Academic Search

We have developed a numerical model to investigate the importance of diffusive chemical fractionation during production and transport of melt in Earth’s upper mantle. The model incorporates new experimental data on the diffusion rates of rare earth elements (REE) in high-Ca pyroxene [Van Orman et al., Contrib. Mineral. Petrol. 141 (2001) 687–703] and pyrope garnet [Van Orman et al., Contrib.

James A. Van Orman; Timothy L. Grove; Nobumichi Shimizu

2002-01-01

4

Bishop tuff revisited: new rare Earth element data consistent with crystal fractionation.  

PubMed

The Bishop Tuff of eastern California is the type example of a high-silica rhyolite that, according to Hildreth, supposedly evolved by liquid-state differentiation. New analyses establish that the Bishop Tuff "earlyllate" rare earth element trend reported by Hildreth mimics the relations between groundmass glasses and whole rocks for allanite-bearing pumice. Differences in elemental concentrations between whole rock and groundmass are the result of phenocryst precipitation; thus the data of Hildreth are precisely those expected to result from crystal fractionation. PMID:17837193

Cameron, K L

1984-06-22

5

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

6

Rare earth element distributions and fractionation in plankton from the northwestern Mediterranean Sea.  

PubMed

Rare earth element (REE) concentrations were measured for the first time in plankton from the northwestern Mediterranean Sea. The REE concentrations in phytoplankton (60-200?m) were 5-15 times higher than those in four size fractions of zooplankton: 200-500?m, 500-1000?m, 1000-2000?m and >2000?m. The concentrations within these zooplankton fractions exhibited the same ranges with some variation attributed to differences in zooplankton taxonomy. The REE concentrations in plankton were poorly related to the reported REE concentrations of seawater, but they correlated well with the calculated REE(3+), concentrations especially with regard to middle REE (MREEs) and heavy REEs (HREEs). Plankton and seawater revealed different PAAS-normalised REE distributions, with the greatest differences observed in the light REEs. Interestingly, a comparison of PAAS-normalized sediment particles from the study of Fowler et al. (1992) showed concentrations of the same order of magnitude and a similar REE distribution without MREE enrichment. Based on this comparison, we propose a conceptual model that emphasizes the importance of biological scavenging of REEs (especially LREEs) in surface waters. PMID:24972173

Strady, Emilie; Kim, Intae; Radakovitch, Olivier; Kim, Guebuem

2015-01-01

7

Rare Earth Element - Humic Acid Interaction: Experimental Evidence for Kinetic and Equilibrium Fractionation in Aqueous Systems.  

NASA Astrophysics Data System (ADS)

Dissolved organic matter (DOM) is well known for it's strong binding capacity for trace metals. In order to better predict the role of DOM in the speciation and transport of trace metals in the environment we coupled capillary electrophoresis (CE), a molecular separation technique, to a Sector Field Inductively Coupled Plasma Mass Spectrometer (SF-ICP-MS). The combination of these two techniques allows for the study of non-labile metal speciation in aquatic samples. By separating Rare Earth Element (REE) complexes with EDTA and Humic Acid's (i.e. ligand competition) we have been able to determine conditional equilibrium binding constants (Kc) and kinetic rate constants for all 14 REE's with Humic (HA) and Fulvic Acids (FA) as a function of pH (6-9) and ionic strength (IS, 0.01-0.1 mol/L). Assuming a 1:1 binding mechanism, logKc values for REE-FA varied from 9.0 (La) to 10.5 (Lu) at pH 6, 0.1 mol/L IS, and 11.7 (La) to 14.6 (Lu) at pH 9, 0.1 mol/L IS. LogKc values for REE-HA were 10.6 (La) to 12.2 (Lu) at pH 6, 0.1 mol/L IS and 13.2 (La) to 16.5 (Lu) at pH 9, 0.1 mol/L IS. Slightly higher values for Kc were obtained at 0.01 mol/L IS. The general observations of stronger REE-HA binding compared to REE-FA, and stronger binding with increasing pH and decreasing IS correlate with our current understanding of metal-DOM interactions (1). Both Kc's as well as kinetic rate constants increase with increasing REE mass number (decreasing ionic radius); a reflection of the well-known lanthanide contraction. This is the first comprehensive metal binding dataset between REE and DOM, and the first experimental evidence for differential equilibrium and kinetic binding behavior between REE's and DOM. The 30-1000 fold increase in binding strength of heavy REE's with DOM provides for a an equilibrium fractionation mechanism that may explain features of the global geochemical REE cycle such as fractionation related to weathering, estuarine mixing, and REE scavenging in the deep ocean (2). The experimental dataset has also been interpreted with the Non-Ideal Competitive Adsorption - Donnan (NICA-Donnan (1)) model for HA and FA metal binding, such that REE-HA binding can be predicted as a function of pH and IS. The NICA-Donnan model is a standard object in the novel object oriented chemical speciation code ORCHESTRA (Objects Representing Chemical Speciation and Transport (3)) that we used to explore the possible effects of pH and IS on fractionating the REE's along an estuarine gradient. (1) Milne, C. J.; Kinniburgh, D. G.; Van Riemsdijk, W. H.; Tipping, E. Environmental Science & Technology 2003, 37, 958-971. (2) Elderfield, H.; Upstillgoddard, R.; Sholkovitz, E. R. Geochimica Et Cosmochimica Acta 1990, 54, 971-991. (3) Meeussen, J. C. L. Environmental Science & Technology 2003, 37, 1175-1182.

Sonke, J. E.; Salters, V. J.; Benedetti, M. F.

2003-12-01

8

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

Microsoft Academic Search

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

E. R. Sholkovitz; W. M. Landing; B. L. Lewis

1994-01-01

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

The capacity of hydrous fluids to transport and fractionate incompatible elements and metals within the Earth's mantle  

NASA Astrophysics Data System (ADS)

silicate melts and aqueous fluids are thought to play critical roles in the chemical differentiation of the Earth's crust and mantle. Yet their relative effects are poorly constrained. We have addressed this issue by measuring partition coefficients for 50 trace and minor elements in experimentally produced aqueous fluids, coexisting basanite melts, and peridotite minerals. The experiments were conducted at 1.0-4.0 GPa and 950-1200°C in single capsules containing (either 40 or 50 wt %) H2O and trace element-enriched basanite glass. This allowed run products to be easily identified and analyzed by a combination of electron microprobe and LAM-ICP-MS. Fluid and melt compositions were reconstructed from mass balances and published solubility data for H2O in silicate melts. Relative to the basanite melt, the solutes from H2O-fluids are enriched in SiO2, alkalis, Ba, and Pb, but depleted in FeO, MgO, CaO, and REE. With increasing pressure, the mutual solubility of fluids and melts increases rapidly with complete miscibility between H2O and basanitic melts occurring between 3.0 and 4.0 GPa at 1100°C. Although LREE are favored over HREE in the fluid phase, they are less soluble than the HFSE (Nb, Ta, Zr, Hf, and Ti). Thus, the relative depletions of HFSE that are characteristic of arc magmas must be due to a residual phase that concentrates HFSE (e.g., rutile). Otherwise, H2O-fluids have the capacity to impart many of the geochemical characteristics that distinguish some rocks and melts from the deep mantle lithosphere (e.g., MARID and lamproites).

Adam, John; Locmelis, Marek; Afonso, Juan Carlos; Rushmer, Tracy; Fiorentini, Marco L.

2014-06-01

11

Ecotoxicity of rare earth elements Rare earth elements (REEs) or rare earth metals is the  

E-print Network

Ecotoxicity of rare earth elements Info Sheet Rare earth elements (REEs) or rare earth metals isolated. Actually, most rare earth elements exist in the Earth's crust in higher concentrations than though most people have never heard of rare earth elements, sev- eral of them govern mankind's modern

Wehrli, Bernhard

12

Impact of plant species, substrate types and porosity on the fractionation of rare-earth elements in plants  

NASA Astrophysics Data System (ADS)

The distribution and content of rare-earth elements (REEs) were determined in two radish species (Raphanus sativus and Raphanus raphanistrum) that were grown under laboratory-controlled conditions, in three substrates consisting in illite for one and in smectite for the two others, the two latter being of the same type but with different porosities. The plants were split into two segments: the leaves and the stems+roots. The results indicate that both species pick up systematically higher amounts of REEs when grown in the illite substrate, considering that the smectite contains about 3 times more REEs. In R. sativus, the REE concentration of the leaves and of the stems+roots, whatever the substrate, ranges from 1.4 to 1.9 ?g/g. After normalization to the substrate in which they grew, the distribution patterns for the leaves of those from illite substrate are nearly flat, but irregular with a positive Eu anomaly. Those for the stems+roots are similar, but enriched in heavy REEs, also with a positive Eu anomaly. The REE concentrations of the leaves and the stems+roots of R. sativus grown in smectite are analytically similar at 1.6 and 1.4 ?g/g, respectively. The REE distribution patterns for the two organs, normalized again to those of the substrate, are very similar, flat with a distinct Eu anomaly. The heavy REE of the stems+roots of R. sativus grown on illite are enriched relative to those of the leaves, and a distinct positive Eu anomaly is observed in both the leaves and stems+roots from species grown on both illite and smectite. In the case of R. raphanistrum, the REE concentrations of the leaves and the stems+roots for those grown in the illite substrate were found to be significantly different at 11.0 and 6.6 ?g/g, respectively. The REE distribution patterns for the two different plant organs normalized to those of the substrates were found to be quite similar, all being quite flat, with a more or less pronounced Ce negative anomaly, and a prominent positive Gd anomaly. When grown on smectite, the REE concentrations of the leaves and the stems+roots were about 7.2 and 6.3 ?g/g, respectively. The REE distribution patterns for the leaves and the stems+roots normalized to the corresponding smectite substrate are very closely similar, each having a nearly flat pattern with a slight but not significant negative Ce anomaly and a similar positive Gd anomaly. When grown on the smectite substrate with a different porosity, the leaves and the stems+roots had significantly higher REE concentrations of 9.3 and 19.7 ?g/g, respectively. Relative to the substrate REE pattern, the two organs had nearly identical flat REE distribution patterns, with a slight negative Ce anomaly and positive Gd and Er anomalies, In summary, the REE take up is more plant species dependent than mineral composition dependent: R. raphanistrum takes up 3.5 to 6.7 times more REEs than R. sativus, depending on the substrate, its porosity and the considered plant segments. Increased substrate porosity favors the pick up of the REEs, but no particular uptake is observed in leaves relative to that in the combined stems and roots. The transfer of the REEs from minerals to plant organs does not appear to induce systematically identical patterns. The effect of the plant species in the elemental uptake suggests that the root exudates are different, with a varied control on the micro-organism activity in the rhizosphere and probably different microbial compounds. New questionings about the identification of the organic compounds that influence and control the process of elemental exchanges activated by the root exudates in the soils within the rhizosphere, are also raised.

Semhi, K.; Clauer, N.; Chaudhuri, S.

2009-04-01

13

[Fractionation and relevant influencing factors of rare-earth elements (REEs) in a soil-plant system].  

PubMed

A potted method was carried out in this paper to research fractionation and some influencing factors (including the concentrations of REEs, humic acids and pH of soil) of the REEs (La, Ce, Nd, Sm, Eu, Gd, Tb and Yb) in a soilplant- system. The results showed that the fractionation model of REEs in red soil used in this experiment was similar to the average fractionation model of soil in China. The fractionation model of REEs in wheat root was similar to the model of the soil, but the fractionation model of REEs in wheat tops was not similar to that one. When REEs were added, the fractionation model of REEs in wheat root was changed similarly to that of the soil, but the model of wheat tops was kept constant. The results suggest the adsorbing way of REEs by wheat root and wheat tops were different. Humic acid showed little influence on the fractionation of REEs in wheat. High pH value (pH = 6.7) promoted the adsorption of light REEs by wheat; whereas, low pH value (pH = 4.2) promoted the adsorption of heavy REEs by wheat. PMID:12619282

Gu, Xueyuan; Wang, Xiaorong; Gu, Zhimang

2002-11-01

14

Fractionation of Volatile Elements by Heating of Solid Allende: Implications for the Source Material of Earth, Moon, and the Eucrite Parent Body  

NASA Astrophysics Data System (ADS)

CI-chondrites have average solar-system abundances of moderately volatile (Na, K, Rb, Sn, etc.) and highly volatile (Cs, Pb, etc.) elements. In most other types of chondrites and in samples from differentiated planetary bodies, these elements are more or less depleted relative to CI chondrites. Volatile-element fractionation occurred either by evaporation or incomplete condensation [1]. Recent data on the isotopic composition of K indicate that depletion of volatiles did not occur by evaporation from a melt of CI-chondritic composition [2]. Evaporative loss from a solid, however, would not necessarily lead to isotopic fractionation of K in the residue [e.g., 3]. In order to study loss of volatile elements from solids, we performed a series of heating experiments under variable oxygen fugacities at temperatures of 1050 degrees C to 1300 degrees C. Residues were analyzed by INAA [4]. We report here additional analyses (K, Rb, Cs, Sn, Pb) of these residues by isotope dilution-SSMS. Results (including Na data from INAA) are shown in Fig. 1. Results at other oxygen fugacities are similar, i.e., there is no strong dependence on fO2, contrary to the results for Au, As, and Zn [4]. Elements are arranged in the order of decreasing condensation temperatures. Depletions increase with increasing temperature and, at least for the 1050 degrees C experiment, with decreasing condensation temperature. The CI- normalized Allende pattern has no strong depletions of Cs and Pb, unlike the experimental results, indicating that evaporation from a solid cannot produce patterns observed in volatile-element-depleted meteorites. Even heating at temperatures as low as 1050 degrees C, affecting alkali elements only slightly, leads to large losses of lead, which are an order of magnitude greater than required for producing CV chondrite patterns. Depletions of these elements apparently occurred in the solar nebula before accretion by incomplete condensation or removal of gas during condensation. Nearly-CI-chondritic Sn/Pb ratios are observed in Allende and other carbonaceous chondrites. Evaporation from a solid leads to a severe increase in this ratio. Similarly, Rb/Cs ratios (about 12) are approximately CI-like in all groups of carbonaceous chondrites, perhaps reflecting the inability of nebular processes to fractionate these ratios. In contrast, terrestrial, lunar, and eucritic rocks have much higher Rb/Cs ratios [5]. As volatile loss from molten magmas is excluded [2], their low Cs contents must be characteristic of the parent material. This may exclude carbonaceous chondrites as source materials of eucrites, the Earth, and the Moon. The low Cs in planetary precursor materials may have been produced by secondary heating of small fragments of solid matter at subsolidus temperatures before final accretion. Equilibrated chondrites also show high Rb/Cs ratios, perhaps indicating mobilization of Cs at metamorphic temperatures. References: [1] Palme H. et al. (1988) in Meteorites and the Early Solar System, 436-461, Univ. of Arizona. [2] Humayan M. and Clayton R. N. (1993) LPSC XXIV, 685-686. [3] Davis A. M. et al. (1990) Nature, 347, 655-658. [4] Wulf A. V. and Palme H. (1991) LPSC XXII, 1527-1528. [5] McDonough W. F. et al. (1992) GCA, 56, 1001-1012. Figure 1 appears here in the hard copy.

Jochum, K. P.; Palme, H.

1993-07-01

15

Controls on the distribution and fractionation of yttrium and rare earth elements in core sediments from the Mandovi estuary, western India  

NASA Astrophysics Data System (ADS)

Mineralogy, major elements (Fe, Mn and Al), rare earths and yttrium (REY) of bulk sediments were analyzed in four gravity cores recovered along the main channel of the Mandovi estuary, western India, to determine the sources and controls on REY distribution. The accelerator mass spectrometer (AMS) ages of total organic carbon indicated modern age for the sediments of the upper estuary and, maximum mean ages of 1588 years AD and 539 years AD for the bottom sediments of the cores in the lower estuary and bay, respectively. The sediments of the upper/middle estuary showed abundant hematite, magnetite and goethite and high Fe, Mn, total-REE (?REE) and Y, while those in the lower estuary/bay showed abundant silicate minerals and relatively low Fe, Mn, ?REE and Y. ?REE showed significant correlation with clay and silt fractions and Y, Al and organic carbon (OC) content of the sediments. The light to heavy REE ratios (LREE/HREE) of sediments were lower than in Post-Archean Australian Shale (PAAS). The PAAS-normalized rare earths and yttrium (REY; Y inserted between Dy and Ho) patterns of sediments showed middle REE (MREE)- and HREE-enrichment with positive Eu anomaly (Eu/Eu*) and variable Ce anomaly (Ce/Ce*). The REY of sediments is primarily controlled by its texture and REE of source sediment, which is ore material-dominated in the upper/middle estuary and silicate material-dominated in the lower estuary/bay. Low LREE/HREE ratios suggest that very fine-grained sediments were carried away from the estuary because of high-energy conditions. Fractionations of REY (Y/Ho, Sm/Nd, Ce/Ce* and Eu/Eu*) are controlled by different mechanisms. High Y/Ho ratios in clayey silts are due to redistribution of Y and Ho by adsorption onto organic-rich, clays. Variations in Sm/Nd ratios are similar to that of Eu/Eu* in cores from the lower estuary/bay and are controlled by mineral constituents of the sediments. Positive Ce and Eu anomalies are inherited from ore material, and ore material and source rocks, respectively. Negative Ce anomaly is related to source rock material and influenced by lanthanum enrichment at certain sediment intervals.

Prajith, A.; Rao, V. Purnachandra; Kessarkar, Pratima M.

2015-01-01

16

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

17

Rare earth element scavenging in seawater  

Microsoft Academic Search

Examinations of rare earth element (REE) adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements (LREEs) are preferentially adsorbed compared to the heavy rare earths (HREEs). Exceptions to this behavior were observed only for silica phases (glass surfaces, acid-cleaned diatomaceous earth, and synthetic SiO 2 ). The affinity of the rare earths

Robert H. Byrne; Ki-Hyun Kim

1990-01-01

18

Rare Earth Elements in the Whitestone Anorthosite.  

E-print Network

?? An analytical procedure is adopted to determine eight rare earth elements in the Whitestone anorthosite, its constituent minerals, and the surrounding metamorphic rocks. Chondrite-normalized… (more)

Barker, Franklin James

1972-01-01

19

Rare Earth Element Mines, Deposits, and Occurrences  

E-print Network

Rare Earth Element Mines, Deposits, and Occurrences by Greta J. Orris1 and Richard I. Grauch2 Open Table 1. Rare earth mineral codes and associated mineral names.......................................................................................6 Table 2. Non-rare earth mineral codes and associated mineral names

Torgersen, Christian

20

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

1957-01-01

21

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

22

Origin of middle rare earth element enrichments in acid waters of a Canadian High Arctic lake  

Microsoft Academic Search

–Middle rare earth element (MREE) enriched rock-normalized rare earth element (REE) patterns of a dilute acidic lake (Colour Lake) in the Canadian High Arctic, were investigated by quantifying whole-rock REE concentrations of rock samples collected from the catchment basin, as well as determining the acid leachable REE fraction of these rocks. An aliquot of each rock sample was leached with

Kevin H Johannesson; Xiaoping Zhou

1999-01-01

23

What about the rare-earth elements  

Technology Transfer Automated Retrieval System (TEKTRAN)

There is insufficient understanding of the nutritional physiology of pecan trees and orchards; thus, affecting nutmeat yield and quality, disease resistance and alternate bearing. An analysis of the rare-earth element composition of pecan and related hickory cousins found that they hyperaccumulate ...

24

Rare earth element scavenging in seawater  

SciTech Connect

Examinations of rare earth element (REE) adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements (LREEs) are preferentially adsorbed compared to the heavy rare earths (HREEs). Exceptions to this behavior were observed only for silica phases. The affinity of the rare earths for surfaces can be strongly affected by thin organic coatings. Glass surfaces which acquired an organic coating through immersion in Tampa Bay exhibited adsorptive behavior typical of organic-rich, rather than glass, surfaces. Models of rare earth distributions between seawater and carboxylate-rich surfaces indicate that scavenging processes which involve such surfaces should exhibit a strong dependence on pH and carbonate complexation. Scavenging models involving carboxylate surfaces produce relative REE abundance patterns in good general agreement with observed shale-normalized REE abundances in seawater. Scavenging by carboxylate-rich surfaces should produce HREE enrichments in seawater relative to the LREEs and may produce enrichments of lanthanum relative to its immediate trivalent neighbors. Due to the origin of distribution coefficients as a difference between REE solution complexation and surface complexation the relative solution abundance patterns of the REEs produced by scavenging reactions can be quite complex.

Byrne, R.H.; Kim, Kihyun (Univ. of South Florida, St. Petersburg (USA))

1990-10-01

25

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

26

Rare earth element systematics in hydrothermal fluids  

SciTech Connect

Rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in Italy, Dominica, Valles Caldera, Salton Sea and the Mid-Atlantic Ridge. The measured abundances show that hydrothermal activity is not expected to affect the REE balance of either continental or oceanic rocks. The REE enrichment of the solutions increases when the pH decreases. High-temperature solutions (> 230{degree}C) percolating through different rock types may show similar REE patterns.

Michard, A. (Centre de Recherches Petrographiques et Geochimiques, Vandoeuvre-les-Nancy (France))

1989-03-01

27

Nitrite complexes of the rare earth elements.  

PubMed

The coordination chemistry of the nitrite anion has been investigated with rare earth elements, and the resulting complexes were structurally characterized. Among them, the first homoleptic examples of nitrite complexes of samarium, ytterbium and yttrium are described. The coordination behavior of the nitrite ion is directly controlled by the ionic radius of the metal cation. While the nitrito ligand is stable in the coordination sphere of cerium(iii), it is readily reduced by SmI2. PMID:24285159

Pouessel, Jacky; Thuéry, Pierre; Berthet, Jean-Claude; Cantat, Thibault

2014-03-21

28

Rare earth elements and permanent magnets (invited)  

NASA Astrophysics Data System (ADS)

Rare earth (RE) magnets have become virtually indispensible in a wide variety of industries such as aerospace, automotive, electronics, medical, and military. RE elements are essential ingredients in these high performance magnets based on intermetallic compounds RECo5, RE2TM17 (TM: transition metal), and RE2TM14B. Rare earth magnets are known for their superior magnetic properties—high induction, and coercive force. These properties arise due to the extremely high magnetocrystalline anisotropy made possible by unique 3d-4f interactions between transition metals and rare earths. For more than 40 years, these magnets remain the number one choice in applications that require high magnetic fields in extreme operating conditions—high demagnetization forces and high temperature. EEC produces and specializes in RECo5 and RE2TM17 type sintered magnets. Samarium and gadolinium are key RE ingredients in the powder metallurgical magnet production processes which include melting, crushing, jet milling, pressing, sintering, and heat treating. The magnetic properties and applications of these magnets will be discussed. We will also briefly discuss the past, current, and future of the permanent magnet business. Currently, over 95% of all pure rare earth oxides are sourced from China, which currently controls the market. We will provide insights regarding current and potential new magnet technologies and designer choices, which may mitigate rare earth supply chain issues now and into the future.

Dent, Peter C.

2012-04-01

29

Note: Portable rare-earth element analyzer using pyroelectric crystal.  

PubMed

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. PMID:24387481

Imashuku, Susumu; Fuyuno, Naoto; Hanasaki, Kohei; Kawai, Jun

2013-12-01

30

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

31

Note: Portable rare-earth element analyzer using pyroelectric crystal  

NASA Astrophysics Data System (ADS)

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; Fuyuno, Naoto; Hanasaki, Kohei; Kawai, Jun

2013-12-01

32

Rare-Earth Element Geochemistry of the Samail Ophiolite near Ibra, Oman  

Microsoft Academic Search

Rare-earth element (REE) analyses of 68 rock and mineral separate samples from the Samail ophiolite clearly. differentiate the various units of the ophiolite suite and indicate that the crustal suite is cogenetic, produced by crystal fractionation of basaltic magma in a spreading ridge magma chamber. Mantle peridotires are residual in rare-earth character, but cannot be clearly related to the overlying

John S. Pallister; Roy J. Knight

1981-01-01

33

Rare-earth element geochemistry of the Samail ophiolite near Ibra, Oman  

Microsoft Academic Search

Rare-earth element (REE) analyses of 68 rocks and mineral separate samples from the Samail ophiolite clearly differentiate the various units of the ophiolite suite and indicate that the crustal suite is cogeneitc, produced by crystal fractionation of basaltic magma in a spreading ridge magma chamber. Mantle peridotities are residual in rare-earth character, but cannot be clearly related to the overlying

John S. Pallister; Roy J. Knight

1981-01-01

34

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

SciTech Connect

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 from different tectonic environments, as well as kimberlite, carbonatite, and high-grade metamorphic rocks, to assess the potential of using zircon REE characteristics to infer the rock types present in sediment source regions. Except for zircon with probable mantle affinities, zircon REE abundances and normalized patterns show little intersample and intrasample variation. To evaluate the actual variation in detrital zircon REE composition in a true sediment of known mixed provenance, zircons from a sandstone sample from the Statfjord Formation (North Sea) were analyzed. Despite a provenance including high-grade metasediment and granitoids and a range in zircon age of 2.82 b.y., the zircon REEs exhibit a narrow abundance range with no systematic differences in pattern shape. These evidences show zircon REE patterns and abundances are generally not useful as indicators of provenance.

Hanchar, J. M.; Finch, R. J.; Hoskin, W. O.; Watson, E. B.; Cherniak, D. J.; Mariano, A. N.; Chemical Engineering; George Washington Univ.; Univ. of Canterbury; Australian National Univ.; Rensselaer Polytechnic Inst.

2001-05-01

35

Rare earth element patterns in biotite, muscovite and tourmaline minerals  

SciTech Connect

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/ g/g to 10/sup -10g//sub g/. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization.

Laul, J.C.; Lepel, E.A.

1986-04-21

36

Activation analysis of rare-earth elements in opium and cannabis samples  

Microsoft Academic Search

Rare earth concentrations in 65 Opium, Cannabis and Cannabis resin samples seized from various parts of world were determined\\u000a by destructive NAA. Great variations in absolute element concentrations, but only small significant differences of rare earth\\u000a concentration ratios were found, indicating inconsiderable biogeochemical fractionation. The mean values of these ratios correspond\\u000a with the relative abundances of the rare earths in

G. Henke; Wilhelms-Universitdt Miinster

1977-01-01

37

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

38

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

39

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

40

Trace Element Fractionation in the Tonga Arc  

NASA Astrophysics Data System (ADS)

Incompatible trace element variations in subduction zone lavas are generally thought to result from variable addition of one or more 'slab components' enriched in fluid mobile elements, to a relatively uniform mantle wedge which contributes the high field strength elements Nb, Ta, Hf and Zr. Depletion in the highly incompatible HFSE Nb and Ta relative to the moderately incompatible Zr and Hf in some arc lavas is presumed to result from previous melt extraction in the back-arc. Together, these independent processes (backarc melting, slab fluid/melt addition) are thought to explain the high U/Nb, Ba/Nb and Zr/Nb ratios, and low absolute concentrations of Nb and Ta in arc lavas. We will present new ICP-MS trace element data for lavas from the Tonga Arc, which have some of the most extreme trace element compositions of all arc lavas. On a global scale, subduction zone lavas with the highest Zr/Nb tend to have the highest Ba/Nb and U/Nb, and the lowest Nb concentrations. Tonga lavas lie at the high Ba/Nb (up to 700), low Nb (down to 0.1 ppm), and high Zr/Nb (up to 180) end of the global arrays. Lavas from individual Tonga islands define correlations between trace element ratios thought to indicate the degree of source depletion or degree of melting (e.g. Zr/Nb) and trace element ratios indicating fluid input (e.g. Ba/Nb). If both Zr and Nb are fluid immobile, then the large range in Zr/Nb cannot result from variable degrees of melting of a homogenous source, and the highest Zr/Nb ratios of 180 require a previously-depleted mantle source. If this depletion had taken place in the back-arc, then the linear correlations between Zr/Nb and Ba/Nb might be explained by addition of a constant amount of Ba- and U-enriched fluid to a variably depleted mantle. However, this is unlikely to produce the excellent correlations observed on the scale of a single Tonga island. Alternatively, correlated Ba/Nb and Zr/Nb could result from a flux melting process, in which the degree of mantle melting is correlated with the degree of fluid input. In this case, however, significant amounts of Zr must be derived from the slab in order to explain the high Zr/Nb ratios. We suggest instead that the range in trace element compositions of lavas from single Tonga islands are best explained by variable mixing of melts derived from two very different mantle sources, which must have different locations within the wedge. Melts of fluid-fluxed, highly depleted mantle close to the trench mix with melts of less depleted mantle containing a smaller slab component, which are generated further from the trench. Recent thermodynamic models of subduction zones predict that melting will occur in several discrete locations within the mantle wedge. Similar correlations between source depletion and fluid input are found in lavas from arcs with no associated backarc. We argue that the depleted HFSE compositions of arc lavas (low Nb and high Zr/Nb) are created within the mantle wedge, and not during melt extraction in the back-arc. If trace element and isotope variations within arc lavas result largely from mixing of melts from discrete source regions in the wedge, the linear arrays defined by many arc lavas in the U-Th disequilibrium diagram may represent mixing arrays, rather than isochrons.

Regelous, M.; Beier, C.; Haase, K. M.

2012-12-01

41

Biogeochemistry of the rare-earth elements with particular reference to hickory trees  

USGS Publications Warehouse

Hickory trees concentrate the rare-earth elements in their leaves to a phenomenal degree and may contain as much as 2300 p.p.m. of total rare earths based on the dry weight of the leaves. The average proportions of the individual elements (atomic percent of the total rare-earth elements) in the leaves are: Y 36, La 16, Ce 14, Pr 2, Nd 20, Sm 1, Eu 0.7, Gd 3, Tb 0.6, Dy 3, Ho 0.7, Er 2, Tm 0.2, Yb 1, and Lu 0.2. The similarity in the proportions of the rare-earth elements in the leaves and in the exchange complex of the soil on which the hickory trees grow indicates that the trees do not fractionate the rare earths appreciably. The variation of the rare-earth elements in the leaves and soils can be explained generally in terms of the relative abundance of the cerium group and the yttrium group, except for the element cerium. The large fluctuations in the proportion of cerium [Ce/(La + Nd) atomic ratios of 0.16 to 0.86] correlate with oxidation-reduction conditions in the soil profile. The substitution of dilute H2SO3 for dilute HC1 in the determination of available rare-earth elements brings about a large increase in the proportion of cerium that is extracted from an oxygenated subsoil. These relationships strongly suggest that quadrivalent cerium is present in oxygenated subsoil and is less available to plants than the other rare-earth elements that do not undergo such a change in valence. A few parts per billion of rare-earth elements have been detected in two samples of ground water. ?? 1958.

Robinson, W.O.; Bastron, H.; Murata, K.J.

1958-01-01

42

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

43

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

44

Partitioning of rare earth, alkali and alkaline earth elements between phenocrysts and acidic igneous magma  

Microsoft Academic Search

Concentrations of rare earth, alkali and alkaline earth elements in phenocryst and groundmass components of pyroclastic dacites have been measured. Mafic mineral rare-earth partition coefficients are much larger in these dacites than in more basic rocks. This may be due to differences in host ion concentrations in basic and acidic magmas. Because of these high partition coefficients, especially for hornblende,

Hiroshi Nagasawa; Charles C. Schnetzler

1971-01-01

45

Rare earth elements in seawater near hydrothermal vents  

Microsoft Academic Search

Rare earth element (REE) patterns in the deep Pacific are strongly depleted in the lighter elements and have a large negative cerium anomaly. These REE patterns and associated concentration-depth profiles are maintained by regeneration in deep waters modified by preferential scavenging of the lighter elements. Scavenging by iron- and manganese-rich hydrothermal plumes might explain why vast areas of sediments far

G. Klinkhammer; H. Elderfield; A. Hudson

1983-01-01

46

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

47

RARE EARTH ELEMENTS IN FLY ASHES AS POTENTIAL INDICATORS OF ANTHROPOGENIC SOIL CONTAMINATION  

SciTech Connect

Studies of rare earth element (REE) content of disposed fly ashes and their potential mobility were neglected for decades because these elements were believed to be environmentally benign. A number of recent studies have now shown that REE may pose a long-term risk to the biosphere. Therefore, there is a critical need to study the REE concentrations in fly ash and their potential mobilization and dispersal upon disposal in the environment. We analyzed the REE content of bulk, size fractionated, and density separated fractions of three fly ash samples derived from combustion of sub bituminous coals from the western United States and found that the concentrations of these elements in bulk ashes were within the range typical of fly ashes derived from coals from the North American continent. The concentrations of light rare earth elements (LREE) such as La, Ce, and Nd, however, tended towards the higher end of the concentration range whereas, the concentrations of middle rare earth elements (MREE) (Sm and Eu) and heavy rare earth elements (HREE) (Lu) were closer to the lower end of the observed range for North American fly ashes. The concentrations of REE did not show any significant enrichment with decreasing particle size, this is typical of nonvolatile lithophilic element behavior during the combustion process. The lithophilic nature of REE was also confirmed by their concentrations in heavy density fractions of these fly ashes being on average about two times more enriched than the concentrations in the light density fractions. Shale normalized average of REE concentrations of fly ashes and coals revealed significant positive anomalies for Eu and Dy. Because of these distinctive positive anomalies of Eu and Dy, we believe that fly ash contamination of soils can be fingerprinted and distinguished from other sources of anthropogenic REE inputs in to the environment.

Mattigod, Shas V.

2003-08-01

48

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

49

Rare earth element association with foraminifera  

NASA Astrophysics Data System (ADS)

Neodymium isotopes are becoming widely used as a palaeoceanographic tool for reconstructing the source and flow direction of water masses. A new method using planktonic foraminifera which have not been chemically cleaned has proven to be a promising means of avoiding contamination of the deep ocean palaeoceanographic signal by detrital material. However, the exact mechanism by which the Nd isotope signal from bottom waters becomes associated with planktonic foraminifera, the spatial distribution of rare earth element (REE) concentrations within the shell, and the possible mobility of REE ions during changing redox conditions, have not been fully investigated. Here we present REE concentration and Nd isotope data from mixed species of planktonic foraminifera taken from plankton tows, sediment traps and a sediment core from the NW Atlantic. We used multiple geochemical techniques to evaluate how, where and when REEs become associated with planktonic foraminifera as they settle through the water column, reside at the surface and are buried in the sediment. Analyses of foraminifera shells from plankton tows and sediment traps between 200 and 2938 m water depth indicate that only ˜20% of their associated Nd is biogenically incorporated into the calcite structure. The remaining 80% is associated with authigenic metal oxides and organic matter, which form in the water column, and remain extraneous to the carbonate structure. Remineralisation of these organic and authigenic phases releases ions back into solution and creates new binding sites, allowing the Nd isotope ratio to undergo partial equilibration with the ambient seawater, as the foraminifera fall through the water column. Analyses of fossil foraminifera shells from sediment cores show that their REE concentrations increase by up to 10-fold at the sediment-water interface, and acquire an isotopic signature of bottom water. Adsorption and complexation of REE3+ ions between the inner layers of calcite contributes significantly to elevated REE concentrations in foraminifera. The most likely source of REE ions at this stage of enrichment is from bottom waters and from the remineralisation of oxide phases which are in chemical equilibrium with the bottom waters. As planktonic foraminifera are buried below the sediment-water interface redox-sensitive ion concentrations are adjusted within the shells depending on the pore-water oxygen concentration. The concentration of ions which are passively redox sensitive, such as REE3+ ions, is also controlled to some extent by this process. We infer that (a) the Nd isotope signature of bottom water is preserved in planktonic foraminifera and (b) that it relies on the limited mobility of particle reactive REE3+ ions, aided in some environments by micron-scale precipitation of MnCO3. This study indicates that there may be sedimentary environments under which the bottom water Nd isotope signature is not preserved by planktonic foraminifera. Tests to validate other core sites must be carried out before downcore records can be used to interpret palaeoceanographic changes.

Roberts, Natalie L.; Piotrowski, Alexander M.; Elderfield, Henry; Eglinton, Timothy I.; Lomas, Michael W.

2012-10-01

50

A rare earth element-rich carbonatite dyke at Bayan Obo, Inner Mongolia, North China  

Microsoft Academic Search

Summary  ¶A carbonatite dyke, extremely enriched in rare earth elements (REE), is reported from Bayan Obo, Inner Mongolia, North China.\\u000a The REE content in the dyke varies from 1?wt% to up to 20?wt%. The light REEs are enriched and highly fractionated relative\\u000a to the heavy REEs, and there is no Eu anomaly. Although carbon isotope ?13C (PDB) values of the carbonatites

X.-M. Yang; X.-Y. Yang; Y.-F. Zheng; M. J. Le Bas

2003-01-01

51

The geochemistry of the Dunedin Volcano, East Otago, New Zealand: Rare earth elements  

Microsoft Academic Search

A variety of alkaline lavas from the Dunedin Volcano have been analyzed for the rare earth elements (REE) La-Yb. The compositions analyzed were: basalt-hawaiite-mugearite-benmoreite; basanite, nepheline hawaiite, nepheline trachyandesite and nepheline benmoreite; trachyte; phonolite. The series from basalt to mugearite shows continuous enrichment in the REE, consistent with a crystal fractionation model involving removal of olivine and clinopyroxene. From mugearite

R. C. Price; S. R. Taylor

1973-01-01

52

Determination of thorium and of rare earth elements in cerium earth minerals and ores  

USGS Publications Warehouse

The conventional oxalate method for precipitating thorium and the rare earth elements in acid solution exhibits definite solubilities of these elements. The present work was undertaken to establish conditions overcoming these solubilities and to find optimum conditions for precipitating thorium and the rare earth elements as hydroxides and sebacates. The investigations resulted in a reliable procedure applicable to samples in which the cerium group elements predominate. The oxalate precipitations are made from homogeneous solution at pH 2 by adding a prepared solution of anhydrous oxalic acid in methanol instead of the more expensive crystalline methyl oxalate. Calcium is added as a carrier. Quantitative precipitation of thorium and the rare earth elements is ascertained by further small additions of calcium to the supernatant liquid, until the added calcium precipitates as oxalate within 2 minutes. Calcium is removed by precipitating the hydroxides of thorium and rare earths at room temperature by adding ammonium hydroxide to pH > 10. Thorium is separated as the sebacate at pH 2.5, and the rare earths are precipitated with ammonium sebacate at pH 9. Maximum errors for combined weights of thorium and rare earth oxides on synthetic mixtures are ??0.6 mg. Maximum error for separated thoria is ??0.5 mg.

Carron, M.K.; Skinner, D.L.; Stevens, R.E.

1955-01-01

53

Exponentially accurate spectral and spectral element methods for fractional ODEs  

NASA Astrophysics Data System (ADS)

Current discretizations of fractional differential equations lead to numerical solutions of low order of accuracy. Here, we present different methods for fractional ODEs that lead to exponentially fast decay of the error. First, we develop a Petrov-Galerkin (PG) spectral method for Fractional Initial-Value Problems (FIVPs) of the form Dt?0u(t)=f(t) and Fractional Final-Value Problems (FFVPs) DT?tu(t)=g(t), where ??(0,1), subject to Dirichlet initial/final conditions. These schemes are developed based on a new spectral theory for fractional Sturm-Liouville problems (FSLPs), which has been recently developed in [1]. Specifically, we obtain solutions to FIVPs and FFVPs in terms of the new fractional (non-polynomial) basis functions, called Jacobi polyfractonomials, which are the eigenfunctions of the FSLP of first kind (FSLP-I). Correspondingly, we employ another space of test functions as the span of polyfractonomial eigenfunctions of the FSLP of second kind (FSLP-II). Subsequently, we develop a Discontinuous Spectral Method (DSM) of Petrov-Galerkin sense for the aforementioned FIVPs and FFVPs, where the basis functions do not satisfy the initial/final conditions. Finally, we extend the DSM scheme to a Discontinuous Spectral Element Method (DSEM) for efficient longer time-integration and adaptive refinement. In these discontinuous schemes, we employ the asymptotic eigensolutions to FSLP-I & -II, which are of Jacobi polynomial forms, as basis and test functions. Our numerical tests confirm the exponential/algebraic convergence, respectively, in p- and h-refinements, for various test cases with integer- and fractional-order solutions.

Zayernouri, Mohsen; Karniadakis, George Em

2014-01-01

54

?-decay of neutron-rich Z?60 nuclei and the origin of rare earth elements  

SciTech Connect

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. [RIKEN Nishina Center, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan and School of Physics and State key Laboratory of Nuclear Physics and Technology, Peking University (China); Nishimura, S.; Lorusso, G.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P. A.; Sakurai, H. [RIKEN Nishina Center, 2-1 Hirosawa, Wako-shi, Saitama 351-0198 (Japan); Xu, Z. Y. [Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033 Tokyo (Japan); Browne, F. [School of Computing Engineering and Mathematics, University of Brighton (United Kingdom); Daido, R.; Fang, Y. F.; Yagi, A.; Nishibata, H.; Odahara, A.; Yamamoto, T. [Department of Physics, Osaka University, Machikaneyama-machi 1-1, Osaka 560-0043 Toyonaka (Japan); Ideguchi, E.; Aoi, N.; Tanaka, M. [Research Center for Nuclear Physics, Osaka University (Japan); Collaboration: EURICA Collaboration; and others

2014-05-02

55

A finite element solution for the fractional advection dispersion equation  

NASA Astrophysics Data System (ADS)

The fractional advection-dispersion equation (FADE) known as its non-local dispersion, has been proven to be a promising tool to simulate anomalous solute transport in groundwater. We present an unconditionally stable finite element (FEM) approach to solve the one-dimensional FADE based on the Caputo definition of the fractional derivative with considering its singularity at the boundaries. The stability and accuracy of the FEM solution is verified against the analytical solution, and the sensitivity of the FEM solution to the fractional order ? and the skewness parameter ? is analyzed. We find that the proposed numerical approach converge to the numerical solution of the advection-dispersion equation (ADE) as the fractional order ? equals 2. The problem caused by using the first- or third-kind boundary with an integral-order derivative at the inlet is remedied by using the third-kind boundary with a fractional-order derivative there. The problems for concentration estimation at boundaries caused by the singularity of the fractional derivative can be solved by using the concept of transition probability conservation. The FEM solution of this study has smaller numerical dispersion than that of the FD solution by Meerschaert and Tadjeran (J Comput Appl Math 2004). For a given ?, the spatial distribution of concentration exhibits a symmetric non-Fickian behavior when ? = 0. The spatial distribution of concentration shows a Fickian behavior on the left-hand side of the spatial domain and a notable non-Fickian behavior on the right-hand side of the spatial domain when ? = 1, whereas when ? = -1 the spatial distribution of concentration is the opposite of that of ? = 1. Finally, the numerical approach is applied to simulate the atrazine transport in a saturated soil column and the results indicat that the FEM solution of the FADE could better simulate the atrazine transport process than that of the ADE, especially at the tail of the breakthrough curves.

Huang, Quanzhong; Huang, Guanhua; Zhan, Hongbin

2008-12-01

56

Heterogeneous accretion and the moderately volatile element budget of Earth.  

PubMed

Several models exist to describe the growth and evolution of Earth; however, variables such as the type of precursor materials, extent of mixing, and material loss during accretion are poorly constrained. High-precision palladium-silver isotope data show that Earth's mantle is similar in 107Ag/109Ag to primitive, volatile-rich chondrites, suggesting that Earth accreted a considerable amount of material with high contents of moderately volatile elements. Contradictory evidence from terrestrial chromium and strontium isotope data are reconciled by heterogeneous accretion, which includes a transition from dominantly volatile-depleted to volatile-rich materials with possibly high water contents. The Moon-forming giant impact probably involved the collision with a Mars-like protoplanet that had an oxidized mantle, enriched in moderately volatile elements. PMID:20466929

Schönbächler, M; Carlson, R W; Horan, M F; Mock, T D; Hauri, E H

2010-05-14

57

Artificial Radioactivity of Dysprosium and other Rare Earth Elements  

Microsoft Academic Search

IN their pioneer work on artificial radioactivity through neutron bombardment, Fermi and his collaborators announced the discovery of the activity of some of the rare earth elements, namely, of lanthanum, praseodymium, neodymium, samarium and gadolinium. Recently, Sugden1 found that terbium shows an appreciable, and europium a very strong, radioactivity after bombardment with neutrons. We find that dysprosium shows an unusually

G. Hevesy; Hilde Levi

1935-01-01

58

Inter-element fractionation and correction in laser ablation inductively coupled plasma mass spectrometry  

E-print Network

Inter-element fractionation and correction in laser ablation inductively coupled plasma mass-element fractionation in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis is one-2 and SY-4) using a UV 266 nm laser. The study showed that the inter-element fractionation depends

Chen, Zhongxing

59

Thermal Conductivity and Element Fractionation in EV Lac  

NASA Astrophysics Data System (ADS)

We present a 100 ks Suzaku observation of the dMe flare star EV Lac, in which the star was captured undergoing a moderate 1500 s flare. During the flare, the count rate increased by about a factor of 50 and the spectrum showed overall enhanced element abundances relative to quiescence. While the quiescent element abundances confirm the inverse first ionization potential (FIP) effect previously documented for EV Lac, with relatively higher depletions for low FIP elements, abundances during the flare spectra show a composition closer to that of the stellar photosphere. We discuss these results in the context of models that explain abundance fractionation in the stellar chromosphere as a result of the ponderomotive force due to Alfvén waves. Stars with FIP or inverse FIP effects arising from differently directed ponderomotive forces may have quite different abundance signatures in their evaporated chromospheric plasma during flares, if the same ponderomotive force also affects thermal conduction downward from the corona. The regulation of the thermal conductivity by the ponderomotive force requires a level of turbulence that is somewhat higher than is normally assumed, but plausible in filamentary conduction models.

Laming, J. Martin; Hwang, Una

2009-12-01

60

The anthropogenic atmospheric elements fraction: A new interpretation of elemental deposits on tree barks  

NASA Astrophysics Data System (ADS)

The superficial deposit on the bark surface of several trees (mainly Fraxinus excelsior L.) was sampled in the experimental station of the university campus in Grenoble (France). Its composition was studied by scanning electron microscopy-energy dispersive X-ray emission (SEM-EDX) and, after digestion, by inductively coupled plasma-mass spectrometry (ICP-MS). The deposit was composed of 81.3% ± 7.4 organic matter, 9.4% ± 4.9 of geogenic minerals issued from the atmosphere (atmospheric geogenic fraction: AGF) and 9.3% ± 2.7 of a mixture of elements which was called anthropogenic atmospheric elements fraction (AAEF). The SEM-EDX analysis showed the presence of particles of geogenic compounds such as different types of silicates, phosphates, carbonates, sulphates, oxides and also particles of metals such as iron or of alloys of Fe-Zn, Fe-Ni, Ni-Cr and Ca sulphates or phosphates. Typical spheres of "fly ashes" composed of pure iron or Al-silicates were detected. Using the SEM-EDX analysis of the deposit and the average local soil composition, an empiric formula for the AGF (without polluting elements) was chosen, which presented a clear analogy with the global formula of the upper continental crust. In the same way, a formula for the pure organic matter fraction was chosen. Withdrawing the elements corresponding to these two fractions allows a tentative estimation of the content of the AAEF which was supposed to better represent the elemental anthropogenic contamination issued from the atmosphere. In the station, most of Sb, Cd, Sn, Pb, Cu, V and Zn were found in the AAEF. This AAEF composition was compared to that of the deposit in a highway tunnel where Pb and Cu were at a very high level. The meaning and the limits of the AAEF concept were critically discussed.

Catinon, Mickaël; Ayrault, Sophie; Clocchiatti, Roberto; Boudouma, Omar; Asta, Juliette; Tissut, Michel; Ravanel, Patrick

61

Rare earth elements activate endocytosis in plant cells Lihong Wanga,b,1  

E-print Network

Rare earth elements activate endocytosis in plant cells Lihong Wanga,b,1 , Jigang Lic,d,1 , Qing (sent for review May 15, 2014) It has long been observed that rare earth elements (REEs) regulate, such as rare earth elements (REEs), have been observed for a long time to be beneficial to plant growth (1, 2

Deng, Xing-Wang

62

Hydrogeochemistry and rare earth element behavior in a volcanically acidified watershed in Patagonia, Argentina  

E-print Network

and analyzed for major ions, trace metals, and rare earth elements (REE). The concentrations of REE in the RioHydrogeochemistry and rare earth element behavior in a volcanically acidified watershed to oxidation of sulfide minerals. D 2005 Elsevier B.V. All rights reserved. Keywords: Rare earth elements

Royer, Dana

63

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. PMID:22355662

Du, Xiaoyue; Graedel, T. E.

2011-01-01

64

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

65

Least squares finite-element solution of a fractional order two-point boundary value problem  

Microsoft Academic Search

In this paper, a theoretical framework for the least squares finite-element approximation of a fractional order differential equation is presented. Mapping properties for fractional dimensional operators on suitable fractional dimensional spaces are established. Using these properties existence and uniqueness of the least squares approximation is proven. Optimal error estimates are proven for piecewise linear trial elements. Numerical results are included

G. J. Fix; J. P. Roof

2004-01-01

66

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

67

Compositional and phase relations among rare earth element minerals  

NASA Technical Reports Server (NTRS)

A review is presented that mainly treats minerals in which the rare-earth elements are essential constituents, e.g., bastnaesite, monazite, xenotime, aeschynite, allanite. The chemical mechanisms and limits of REE substitution in some rock-forming minerals (zircon, apatite, titanite, garnet) are also derived. Vector representation of complex coupled substitutions in selected REE-bearing minerals is examined and some comments on REE-partitioning between minerals as related to acid-based tendencies and mineral stabilities are presented. As the same or analogous coupled substitutions involving the REE occur in a wide variety of mineral structures, they are discussed together.

Burt, D. M.

1989-01-01

68

Solar Wind Fractionation — Isotopic and Elemental — and Implications for Solar Compositions and Future Genesis Analyses  

NASA Astrophysics Data System (ADS)

Fractionation between solar wind and the solar photosphere is substantial, both for elements and isotopes. GENESIS measurements are key to understanding these fractionations, which will in turn provide more accurate solar compositions.

Wiens, R. C.; Reisenfeld, D. B.; Heber, V. S.; Burnett, D. S.

2010-03-01

69

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

70

Trace Elemental Imaging of Rare Earth Elements Discriminates Tissues at Microscale in Flat Fossils  

PubMed Central

The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809

Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B.; Cohen, Serge X.; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

2014-01-01

71

Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.  

PubMed

The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809

Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B; Cohen, Serge X; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

2014-01-01

72

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

73

NREL Highlights SCIENCE These polycrystalline cells use Earth-abundant elements.  

E-print Network

NREL Highlights SCIENCE These polycrystalline cells use Earth-abundant elements. NREL scientists (CZTSe) solar cells, which are based on non-toxic, Earth-abundant elements. Recently, NREL demonstrated. Potential Impact CZTSe cells use Earth-abundant materials that provide environmental benefits (non

74

The elements of the Earth's magnetism and their secular changes between 1550 and 1915  

NASA Technical Reports Server (NTRS)

The results of an investigation about the magnetic agents outside the Earth's surface as well as the Earth's magnetic elements for the epochs 1550, 1900, 1915 are presented. The secular changes of the Earth's magnetic elements during the time interval 1550 - 1900 are also included.

Fritsche, H.

1983-01-01

75

Partitioning of light lithophile elements during basalt eruptions on Earth and application to Martian shergottites  

NASA Astrophysics Data System (ADS)

An enigmatic record of light lithophile element (LLE) zoning in pyroxenes in basaltic shergottite meteorites, whereby LLE concentrations decrease dramatically from the cores to the rims, has been interpreted as being due to partitioning of LLE into a hydrous vapor during magma ascent to the surface on Mars. These trends are used as evidence that Martian basaltic melts are water-rich (McSween et al., 2001). Lithium and boron are light lithophile elements (LLE) that partition into volcanic minerals and into vapor from silicate melts, making them potential tracers of degassing processes during magma ascent to the surface of Earth and of other planets. While LLE degassing behavior is relatively well understood for silica-rich melts, where water and LLE concentrations are relatively high, very little data exists for LLE abundance, heterogeneity and degassing in basaltic melts. The lack of data hampers interpretation of the trends in the shergottite meteorites. Through a geochemical study of LLE, volatile and trace elements in olivine-hosted melt inclusions from Kilauea Volcano, Hawaii, it can be demonstrated that lithium behaves similarly to the light to middle rare Earth elements during melting, magma mixing and fractionation. Considerable heterogeneity in lithium and boron is inherited from mantle-derived primary melts, which is dominant over the fractionation and degassing signal. Lithium and boron are only very weakly volatile in basaltic melt erupted from Kilauea Volcano, with vapor-melt partition coefficients <0.1. Degassing of LLE is further inhibited at high temperatures. Pyroxene and associated melt inclusion LLE concentrations from a range of volcanoes are used to quantify lithium pyroxene-melt partition coefficients, which correlate negatively with melt H2O content, ranging from 0.13 at low water contents to <0.08 at H2O contents >4 wt%. The observed terrestrial LLE partitioning behavior is extrapolated to Martian primitive melts through modeling. The zoning observed in the shergottite pyroxenes is only consistent with degassing of LLE from a Martian melt near its liquidus temperature if the vapor-melt partition coefficient was an order of magnitude larger than observed on Earth. The range in LLE and trace elements observed in shergottite pyroxenes are instead consistent with concurrent mixing and fractionation of heterogeneous melts from the mantle.

Edmonds, Marie

2015-02-01

76

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

77

Insights into early Earth from Barberton komatiites: Evidence from lithophile isotope and trace element systematics  

NASA Astrophysics Data System (ADS)

Major, minor, and lithophile trace element abundances and Nd and Hf isotope systematics are reported for two sets of remarkably fresh, by Archean standards, samples of komatiitic lavas from the 3.48 Ga Komati and the 3.27 Ga Weltevreden Formations of the Barberton Greenstone Belt (BGB) in South Africa. These data are used to place new constraints on the thermal history of the early Archean mantle, on the timing of its differentiation, and on the origin and chemical nature of early mantle reservoirs and their evolution through time. Projected moderate to strong depletions of highly incompatible lithophile trace elements and water in the mantle sources of both komatiite systems, combined with the partitioning behavior of V during lava differentiation, are consistent with anhydrous conditions during generation of the komatiite magmas. Komati and Weltevreden lavas are inferred to have erupted with temperatures of ?1600 °C, and, thus, represent the hottest known lavas on Earth. The calculated mantle potential temperatures of ?1800 °C for both komatiite systems are 150-200 °C higher than those of contemporary ambient mantle. Combined, these observations are consistent with the origin of these BGB komatiite magmas in mantle plumes in the lower mantle. New Sm-Nd and Lu-Hf isotopic data allow precise determination of initial ?143Nd = +0.46 ± 0.10 and +0.50 ± 0.11 and initial ?176Hf = +1.9 ± 0.3 and +4.7 ± 0.8 for the Komati and the Weltevreden system komatiites, respectively. These positive initial values reflect prior fractionation of Sm/Nd and Lu/Hf in the mantle early in Earth history. Conversely, ?142Nd values are 0.0 ± 2.4 and +2.2 ± 4.1 for the Komati and the Weltevreden systems, respectively. These values overlap, within uncertainties, those of modern terrestrial rocks, thus, limiting the magnitudes of possible Sm/Nd fractionations generated by early Earth processes in the sources of these rocks. Combined 142,143Nd and Hf isotope and lithophile trace element systematics are consistent with formation and long-term isolation of deep-seated mantle domains with fractionated Sm/Nd and Lu/Hf at ca. 4400 Ma. These domains were likely generated as a result of crystallization of a primordial magma ocean, with Mg-perovskite and minor Ca-perovskite acting as fractionating phases. The inferred mantle domains were evidently mixed away by 2.7 Ga on the scale of mantle reservoirs sampled by late Archean komatiite lavas emplaced worldwide.

Puchtel, I. S.; Blichert-Toft, J.; Touboul, M.; Walker, R. J.; Byerly, G. R.; Nisbet, E. G.; Anhaeusser, C. R.

2013-05-01

78

Rare earth element partitioning between titanite and silicate melts: Henry's law revisited  

E-print Network

Rare earth element partitioning between titanite and silicate melts: Henry's law revisited Stefan earth elements (REE) between titanite and a range of different silicate melts. Our results show that Henry's law of trace element partitioning depends on bulk composition, the available partners

79

Online preconcentration ICP-MS analysis of rare earth elements in seawater  

NASA Astrophysics Data System (ADS)

The rare earth elements (REEs) with their systematically varying properties are powerful tracers of continental inputs, particle scavenging intensity and the oxidation state of seawater. However, their generally low (˜pmol/kg) concentrations in seawater and fractionation potential during chemical treatment makes them difficult to measure. Here we report a technique using an automated preconcentration system, which efficiently separates seawater matrix elements and elutes the preconcentrated sample directly into the spray chamber of an ICP-MS instrument. The commercially available "seaFAST" system (Elemental Scientific Inc.) makes use of a resin with ethylenediaminetriacetic acid and iminodiacetic acid functional groups to preconcentrate REEs and other metals while anions and alkali and alkaline earth cations are washed out. Repeated measurements of seawater from 2000 m water depth in the Southern Ocean allows the external precision (2?) of the technique to be estimated at <23% for all REEs and <15% for most. Comparison of Nd concentrations with isotope dilution measurements for 69 samples demonstrates that the two techniques generally agree within 15%. Accuracy was found to be good for all REEs by using a five point standard addition analysis of one sample and comparing measurements of mine water reference materials diluted with a NaCl matrix with recommended values in the literature. This makes the online preconcentration ICP-MS technique advantageous for the minimal sample preparation required and the relatively small sample volume consumed (7 mL) thus enabling large data sets for the REEs in seawater to be rapidly acquired.

Hathorne, Ed C.; Haley, Brian; Stichel, Torben; Grasse, Patricia; Zieringer, Moritz; Frank, Martin

2012-01-01

80

Rare earth elements activate endocytosis in plant cells.  

PubMed

It has long been observed that rare earth elements (REEs) regulate multiple facets of plant growth and development. However, the underlying mechanisms remain largely unclear. Here, using electron microscopic autoradiography, we show the life cycle of a light REE (lanthanum) and a heavy REE (terbium) in horseradish leaf cells. Our data indicate that REEs were first anchored on the plasma membrane in the form of nanoscale particles, and then entered the cells by endocytosis. Consistently, REEs activated endocytosis in plant cells, which may be the cellular basis of REE actions in plants. Moreover, we discovered that a portion of REEs was successively released into the cytoplasm, self-assembled to form nanoscale clusters, and finally deposited in horseradish leaf cells. Taken together, our data reveal the life cycle of REEs and their cellular behaviors in plant cells, which shed light on the cellular mechanisms of REE actions in living organisms. PMID:25114214

Wang, Lihong; Li, Jigang; Zhou, Qing; Yang, Guangmei; Ding, Xiao Lan; Li, Xiaodong; Cai, Chen Xin; Zhang, Zhao; Wei, Hai Yan; Lu, Tian Hong; Deng, Xing Wang; Huang, Xiao Hua

2014-09-01

81

Rare earth elements in sinters from the geothermal waters (hot springs) on the Tibetan Plateau, China  

NASA Astrophysics Data System (ADS)

The mineralogical and geochemical composition of sinters from the geothermal areas on the Tibetan Plateau was determined. They occur as siliceous, salty and calcareous sinters but biogenic siliceous sinters were also found. The analyses indicate that there are no distinct inter -element relationships between individual rare earth elements (REEs) and other elements. Formed from the same geothermal water, the mineralogical and chemical composition of the sinters is influenced by their genesis and formation conditions. The REE distributions depend on the origin of the sinters. Fe-Mn phases in sinters tend to scavenge more REEs from geothermal water. Neither the REE fractionation nor the Ce anomaly seems to be associated with Fe-Mn phases in the sinters. The fourth tetrads of some sinters display weak W-type (concave) effects. In contrast, the third tetrads present large effects in some sinters due to positive Gd anomalies. The origin of the positive Eu anomalies in some sinters seems to be caused by preferential dissolution of feldspars during water-rock interaction. The complexing ligands in geothermal water may contribute significantly to the fractionation of REEs in sinters. The dominant CO32- and HCO3- complexing in geothermal water favors enrichment of heavy REEs in calcareous sinters.

Feng, Jin-Liang; Zhao, Zhen-Hong; Chen, Feng; Hu, Hai-Ping

2014-10-01

82

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

83

Elemental processes of transport and energy conversion in Earth's magnetosphere  

NASA Astrophysics Data System (ADS)

In the last 5 years observations from several missions and ground based observatories have honed in on the most elemental aspects of flux transport and energy conversion. Dipolarization fronts and their counterpart in the distant magnetotail "anti-dipolarization" fronts, which together are refered to herein as "reconnection fronts", usher the recently reconnected flux tubes from the near-Earth X-points and in the process convert magnetic energy to particle energy and wave radiation. On the tailward side they are responsible for plasmoid formation and acceleration. On the earthward side they result in elemental substorm current wedges or wedglets, which were initially postulated from ground observations alone. Recent observations have revealed how the interaction of wedgelets and the inner magnetosphere takes place. Questions remain with regards to the physics of the energy transfer process from global magnetic energy to local heating and waves, and with regards to the initiation of the X-point activations in space. Observations indicate that the latter may be induced by polar cap or dayside activity, suggesting a direct link between dayside reconnection and nightside phenomena. The likely causal sequence of events and open questions in light of these recent observations, and the field's outlook in anticipation of upcoming coordinated observations from the international Heliophysics System Observatory will be discussed.

Angelopoulos, Vassilis

84

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

85

ANALYSIS OF A FRACTIONAL SYSTEM COMPOSED OF AN I-ELEMENT AND A FRACTANCE  

E-print Network

ANALYSIS OF A FRACTIONAL SYSTEM COMPOSED OF AN I-ELEMENT AND A FRACTANCE Xavier MOREAU, Pascal composed of a storage I-element and a fractance. The fractance is approximate by a network of 4 identical with both systems is illustrated versus variations of the I-element. Copyright © 2008 IFAC Keywords

Paris-Sud XI, Université de

86

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

87

Effects of the accumulation of the rare earth elements on soil macrofauna community  

Microsoft Academic Search

The accumulation of rare earth elements (REEs) in soil has occurred due to the pollution caused by the exploitation of rare earth resources and the wide rare earth fertilizers in agriculture. The accumulation of REEs has a toxic effect on the soil macrofauna community. 12 study samples were collected near a mine tailings dam with a large amount of REEs

Jinxia LI; Mei HONG; Xiuqin YIN; Jiliang LIU

2010-01-01

88

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

89

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

90

Geochemical prospecting for rare earth elements using termite mound materials  

NASA Astrophysics Data System (ADS)

The Blockspruit fluorite prospect, located in North West State of the Republic of South Africa, occurs within an actinolite rock zone that was emplaced into the Kenkelbos-type granite of Proterozoic age. There are a large number of termite mounds in the prospect. For geochemical prospecting for rare earth elements (REEs), in total, 200 samples of termite mound material were collected from actinolite rock and granite zones in the prospect. Geochemical analyses of these termite mound materials were conducted by two methods: portable X-ray fluorescence (XRF) spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS). Comparison of the two methods broadly indicates positive correlations of REEs (La, Ce, Pr, Nd, and Y), in particular Y and La having a strong correlation. As the result of modal abundance analyses, the actinolite rock at surface mainly consists of ferro-actinolite (89.89 wt%) and includes xenotime (0.26 wt%) and monazite (0.21 wt%) grains as REE minerals. Termite mound materials from actinolite rock also contain xenotime (0.27 wt%) and monazite (0.41 wt%) grains. In addition, termite mound materials from the actinolite rock zone have high hematite and Fe silicate contents compared to those from granite zone. These relationships suggest that REE minerals in termite mound materials originate form actinolite rock. Geochemical anomaly maps of Y, La, and Fe concentrations drawn based on the result of the portable XRF analyses show that high concentrations of these elements trend from SW to NE which broadly correspond to occurrences of actinolite body. These results indicate that termite mounds are an effective tool for REE geochemical prospection in the study area for both light REEs and Y, but a more detailed survey is required to establish the distribution of the actinolite rock body.

Horiuchi, Yu; Ohno, Tetsuji; Hoshino, Mihoko; Shin, Ki-Cheol; Murakami, Hiroyasu; Tsunematsu, Maiko; Watanabe, Yasushi

2014-12-01

91

Effects of spraying rare earths on contents of rare Earth elements and effective components in tea.  

PubMed

Rare earth (RE) fertilizer is widely applied in China to increase the yield and the quality of crops including tea. However, the effects of spraying RE fertilizer on the contents of rare earth elements (REE) and effective components in tea are unknown. The results from basin and field experiments show that the values of the REE concentrations in new shoots of tea plants and the concentration of REE in the soil (REE/REEs) either from control basins or from treatment basins were smaller than those in other parts of tea plant and similar between control and treatment. The longer the interval between spraying RE fertilizer and picking the shoots of tea plants, the less the effects from spraying. About 80% summation operator REE (the sum of the concentrations of 15 REE) in tea, whether it came from spraying or not, was insoluble in the infusion. About 10% the soluble REE of summation operator REE in tea infusion was bound to polysaccharide, and the amount of REE bound polysaccharide decreased over time. At least a 25 day safety interval is needed between spraying and picking if the microelement fertilizer is used, in order to enhance tea output and to ensure tea safety. PMID:14582968

Wang, Dongfeng; Wang, Changhong; Ye, Sheng; Qi, Hongtao; Zhao, Guiwen

2003-11-01

92

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

93

Recovery of rare earth elements from the sulfothermophilic red alga Galdieria sulphuraria using aqueous acid.  

PubMed

The demand for rare earth elements has increased dramatically in recent years because of their numerous industrial applications, and considerable research efforts have consequently been directed toward recycling these materials. The accumulation of metals in microorganisms is a low-cost and environmentally friendly method for the recovery of metals present in the environment at low levels. Numerous metals, including rare earth elements, can be readily dissolved in aqueous acid, but the efficiency of metal biosorption is usually decreased under the acidic conditions. In this report, we have investigated the use of the sulfothermophilic red alga Galdieria sulphuraria for the recovery of metals, with particular emphasis on the recovery of rare earth metals. Of the five different growth conditions investigated where G. sulphuraria could undergo an adaptation process, Nd(III), Dy(III), and Cu(II) were efficiently recovered from a solution containing a mixture of different metals under semi-anaerobic heterotrophic condition at a pH of 2.5. G. sulphuraria also recovered Nd(III), Dy(III), La(III), and Cu(II) with greater than 90 % efficiency at a concentration of 0.5 ppm. The efficiency remained unchanged at pH values in the range of 1.5-2.5. Furthermore, at pH values in the range of 1.0-1.5, the lanthanoid ions were collected much more efficiently into the cell fractions than Cu(II) and therefore successfully separated from the Cu(II) dissolved in the aqueous acid. Microscope observation of the cells using alizarin red suggested that the metals were accumulating inside of the cells. Experiments using dead cells suggested that this phenomenon was a biological process involving specific activities within the cells. PMID:25283836

Minoda, Ayumi; Sawada, Hitomi; Suzuki, Sonoe; Miyashita, Shin-Ichi; Inagaki, Kazumi; Yamamoto, Takaiku; Tsuzuki, Mikio

2015-02-01

94

Distribution of rare earth elements in an alluvial aquifer affected by acid mine drainage: the Guadiamar aquifer (SW Spain).  

PubMed

This work analyses the spatial distribution, the origin, and the shale-normalised fractionation patterns of the rare earth elements (REE) in the alluvial aquifer of the Guadiamar River (south-western Spain). This river received notoriety in April 1998 for a spill that spread a great amount of slurry (mainly pyrites) and acid waters in a narrow strip along the river course. Groundwaters and surface waters were sampled to analyse, among other elements, the REEs. Their spatial distribution shows a peak close to the mining region, in an area with low values of pH and high concentrations of sulphates and other metals such as Zn, Cu, Co, Ni, Pb, and Cd. The patterns of shale-normalised fractionation at the most-contaminated points show an enrichment in the middle rare earth elements (MREE) with respect to the light (LREE) and heavy (HREE) ones, typical of acid waters. The Ce-anomaly becomes more negative as pH increases, due to the preferential fractionation of Ce in oxyhydroxides of Fe. PMID:15701392

Olías, M; Cerón, J C; Fernández, I; De la Rosa, J

2005-05-01

95

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

NASA Technical Reports Server (NTRS)

There are currently several hypotheses on the origin of volatile siderophile elements in the Earth. One hypothesis is that they were added during Earth s accretion and core formation and mobilized into the metallic core [1], others claim multiple stage origin [2], while some hypothesize that volatiles were added after the core already formed [3]. Several volatile siderophile elements are depleted in Earth s mantle relative to the chondrites, something which continues to puzzle many scientists. This depletion is likely due to a combination of volatility and core formation. The Earth s core is composed of Fe and some lighter constituents, although the abundances of these lighter elements are unknown [4]. Si is one of these potential light elements [5] although few studies have analyzed the effect of Si on metal-silicate partitioning, in particular the volatile elements. As, In, Ge, and Sb are trace volatile siderophile elements which are depleted in the mantle but have yet to be extensively studied. The metal-silicate partition coefficients of these elements will be measured to determine the effect of Si. Partition coefficients depend on temperature, pressure, oxygen fugacity, and metal and silicate composition and can constrain the concentrations of volatile, siderophile elements found in the mantle. Reported here are the results from 13 experiments examining the partitioning of As, In, Ge, and Sb between metallic and silicate liquid. These experiments will examine the effect of temperature, and metal-composition (i.e., Si content) on these elements in or-der to gain a greater understanding of the core-mantle separation which occurred during the Earth s early stages. The data can then be applied to the origin of volatile elements in the Earth.

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

2012-01-01

96

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

E-print Network

by chemical diffusion between a natural basalt and rhyolite. The thermal isotopic fractionations for isotopes of the same element. The iron isotopic mea- surements of the basalt­rhyolite diffusion couple by chemical diffusion between molten basalt and rhyolite (Richter et al., 2003) and large fractionations

Watkins, Jim

97

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

98

Recovery and Separation of Rare Earth Elements Using Salmon Milt  

PubMed Central

Recycling rare earth elements (REEs) used in advanced materials such as Nd magnets is important for the efficient use of REE resources when the supply of several REEs is limited. In this work, the feasibility of using salmon milt for REE recovery and separation was examined, along with the identification of the binding site of REEs in salmon milt. Results showed that (i) salmon milt has a sufficiently high affinity to adsorb REEs and (ii) the adsorption capacity of the milt is 1.04 mEq/g, which is comparable with that of commercial cation exchange resin. Heavier REEs have higher affinity for milt. A comparison of stability constants and adsorption patterns of REEs discussed in the literature suggests that the phosphate is responsible for the adsorption of REE in milt. The results were supported by dysprosium (Dy) and lutetium (Lu) LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. The REE-P shell was identified for the second neighboring atom, which shows the importance of the phosphate site as REE binding sites. The comparison of REE adsorption pattern and EXAFS results between the milt system and other adsorbent systems (cellulose phosphate, Ln-resin, bacteria, and DNA-filter hybrid) revealed that the coordination number of phosphate is correlated with the slope of the REE pattern. The separation column loaded with milt was tested to separate REE for the practical use of salmon milt for the recovery and separation of REE. However, water did not flow through the column possibly because of the hydrophobicity of the milt. Thus, sequential adsorption–desorption approach using a batch-type method was applied for the separation of REE. As an example of the practical applications of REE separation, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste by a batch-type method using salmon milt. PMID:25490035

Takahashi, Yoshio; Kondo, Kazuhiro; Miyaji, Asami; Watanabe, Yusuke; Fan, Qiaohui; Honma, Tetsuo; Tanaka, Kazuya

2014-01-01

99

Nanomaterials made of earth-abundant elements for photovoltaics  

NASA Astrophysics Data System (ADS)

Of the many types of solar cells currently under exploration, multijunction photovoltaics (MJPVs) are of the most interest due to their record-breaking solar energy conversion efficiencies (over 40%). However, MJPV device fabrication is expensive because they require a costly synthesis technique that utilizes rare elements such as gallium, arsenic, and indium. To resolve this issue, our efforts have been focused on the replacement of the thin-film materials currently employed in MJPVs with a more earth-abundant alternative, Zn-alloyed iron pyrite (ZnxFe(1-x)S2). The synthesis of ZnxFe(1-x)S2 nanoparticles is of particular interest because a nanoparticle 'ink' can be inserted into a roll-to-roll processor, which is an inexpensive technique of creating defect-free thin-films for electronics. The first part of this work explores the synthesis of Zn-alloyed iron pyrite nanoparticles via the modification of a solvothermal method from the literature. The nanoparticles generated using this method at first indicated zinc-alloying was successful; yet, further studies into the electronic structure of the particles necessitated the addition of a spin-purification step to ensure only highly soluble particles remained for spin-coating deposition. Compositional and structural analysis of the particles that remained after the additional spin-purification step showed evidence of both the ZnS and FeS2 phases. The second part of this work focuses on the development of an alternative method of generating iron pyrite nanoparticles, which would also eventually be used for zinc-alloying. The two approaches focused on are a hydrothermal method in an acid-digestion bomb and a non-injection solvothermal method in an inert environment. The synthesized particles using these methods were phase-pure and did not contain any detectable quantity of other iron sulfides.

Molk, Doreen

100

ABUNDANCE OF TRACE AND MINOR ELEMENTS IN ORGANIC AND MINERAL FRACTIONS OF COAL  

EPA Science Inventory

The report gives results of subjecting 27 U.S. coals to float/sink, acid, and ion-exchange treatments. From these treatments, coal fractions were obtained and analyzed to determine the organic and mineral associations of 45 elements. Of the elements studied, B, Be, Br, Ge, and Sb...

101

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...

102

Quantifying Surface Kinetic Fractionations for Isotopes and Trace Elements in Calcite Precipitated from Aqueous Solution  

NASA Astrophysics Data System (ADS)

The isotopic ratios and trace element concentrations in calcite and other carbonate minerals form the basis for several paleoenvironmental indicators that are relied upon to reconstruct past Earth climates and ocean processes. Most of these carbonate minerals form at low temperatures (0 to 30C) and consequently are unlikely to have precipitated from aqueous solutions at equilibrium. The non-equilibrium nature of the precipitation process is well illustrated by the experimentally demonstrated precipitation rate-dependence of parameters such as the Ca and O isotopic composition, and the Sr, Mg, and Mn concentrations of calcite. We have been focused on understanding how to predict the magnitude and controls on these kinetic effects using a general transition-state theory approach, as well as models of ion-by-ion growth, molecular dynamics simulations of the desolvation step required for addition of cations to a mineral surface, and further experiments that involve carefully controlled solution compositions and crystal growth rates. Although models have been proposed that invoke diffusion as the primary control on the non-equilibrium aspects of calcite precipitation, it is relatively easy to show that diffusion is not likely to be the primary controlling process. We have focused on understanding the kinetic effects operating at and near the mineral surface, which are undeniably present and important, and appear to be of the correct magnitude and direction to account for observations in both laboratory and natural calcites. The approach we are using is also applicable to higher temperature aqueous precipitation. There are indications from Ca isotopes that similar surface kinetic effects occur at temperatures of 300 to 400C. Kinetic isotope and trace element effects are critically dependent on molecular exchange rates between the mineral surface and the aqueous solution, and the ratio of these rates to the net crystal growth rate. The challenge is to predict and/or measure these rates, which are dependent in a complex fashion on solution saturation state, cation/anion ratios, ionic strength, and other aspects of solution composition. In effect, trace elements and isotopes can provide a measure of these rates, and the derived rates from available experimental data are broadly compatible with measured calcite dissolution and precipitation rates and their dependence on solution composition. Overall, it appears possible to develop a comprehensive framework for understanding kinetic trace element and isotopic fractionation effects during precipitation of minerals from aqueous solution, and to constrain the important controlling parameters using a combination of experiments and simulations.

DePaolo, D. J.; Nielsen, L. C.; Hofmann, A. E.; DeYoreo, J.; Gagnon, A. C.; Watkins, J. M.; Ryerson, F. J.; Brown, S. T.

2011-12-01

103

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

104

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

105

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

106

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., II; McCafferty, Anne E.

2014-01-01

107

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

108

Modelling of Rare Earth Elements Complexation With Humic Acid  

NASA Astrophysics Data System (ADS)

The binding of rare earth elements (REE) to humic acid (HA) was studied by combining Ultrafiltration and ICP- MS techniques. REE-HA complexation experiments were performed at various pH conditions (ranging from 2 to 10.5) using a standard batch equilibration method. Results show that the amount of REE bound to HA strongly increase with increasing pH. Moreover, a Middle REE (MREE) downward concavity is evidenced by REE distribution patterns at acidic pH. Modelling of the experimental data using Humic Ion Binding Model VI provided a set of log KMA values (i.e. the REE-HA complexation constants specific to Model VI) for the entire REE series. The log KMA pattern obtained displays a MREE downward concavity. Log KMA values range from 2.42 to 2.79. These binding constants are in good agreement with the few existing datasets quantifying the binding of REE with humic substances except a recently published study which evidence a lanthanide contraction effect (i.e. continuous increase of the constant from La to Lu). The MREE downward concavity displayed by REE-HA complexation pattern determined in this study compares well with results from REE-fulvic acid (FA) and REE-acetic acid complexation studies. This similarity in the REE complexation pattern shapes suggests that carboxylic groups are the main binding sites of REE in HA. This conclusion is further supported by a detailed review of published studies for natural, organic-rich, river- and ground-waters which show no evidence of a lanthanide contraction effect in REE pattern shape. Finally, application of Model VI using the new, experimentally determined log KMA values to World Average River Water confirms earlier suggestions that REE occur predominantly as organic complexes (> 60 %) in the pH range between 5-5.5 and 7-8.5 (i.e. in circumneutral pH waters). The only significant difference as compared to earlier model predictions made using estimated log KMA values is that the experimentally determined log KMA values predict a significantly higher amount of Light REE bound to organic matter under alkaline pH conditions. Taken as a whole, the new experimental results shed additional light on the processes that govern REE pattern shapes in natural, organic-rich waters.

Pourret, O.; Davranche, M.; Gruau, G.; Dia, A.

2006-12-01

109

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

110

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

111

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

112

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. PMID:24737957

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

2014-01-01

113

EXTREME FRACTIONATION IN RARE.ELEMENT GRANITIC PEGMATITES: SELECTED EXAMPLES OF DATA AND MECHANISMS  

Microsoft Academic Search

Granitic pegmatites of the rare_element (and miarolitic) class display extreme fractionation and accumulation.of rare lithophile elements, beyond the limits observed in other igneous and postmagmatic assemblages. Enrichment in Li and -Cs leads to precipitation of rock-forming spodumene, petalite, Li-phosphates or lepidolite, and pollucite. These gqeoes-can be interpreted as crystallochemically conditioned Li- and-Csbased feldspathoids, crystallizing along with (and after) the last

ROBERT E. MEINTZER; ALAN J. ANDERSON

114

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

115

Distribution of titanium and the rare earth elements between peridotitic minerals  

Microsoft Academic Search

The concentrations of titanium and rare earth elements (REE) in olivines, orthopyroxenes, clinopyroxenes and spinels from four anhydrous, spinel-bearing peridotite xenoliths have been determined. The distribution of titanium (used as an analogue for the high field strength elements: HFSE) relative to the REE between clinopyroxenes and orthopyroxenes varies as a function of the whole rock composition and modal mineralogy. The

W. F. McDonough; H.-G. Stosch; N. G. Ware

1992-01-01

116

Volatility Fractionation of REE and Other Trace Elements During Vacuum Evaporation  

NASA Astrophysics Data System (ADS)

Volatility-fractionated REE patterns were first recognized in calcium-, aluminum-rich inclusions (CAIs) in meteorites over 20 years ago [1]. Such REE patterns can be modeled quite well by equilibrium thermodynamic calculations [2,3,4], but kinetic effects on fractionation of trace elements between gas and solids or liquids have remained less well-known. We have previously reported on experiments in which melts of initial REE-doped chondritic composition [5] and perovskite composition [6] were evaporated in vacuo. In both series of experiments, residues were formed that had large negative Ce anomalies and small negative Pr and Eu anomalies, but no other significant REE fractionations were observed. In an effort to produce more extensive fractionation of REE and other refractory elements, we made a new, more refractory, starting material (stoichiometric CaTiO3 doped with a number of refractory trace elements in chondritic proportions to a total "trace" element level of 5 wt%) and evaporated it under vacuum at a higher temperature (2150 degrees C) than the earlier experiments (1800-2000 degrees C). The results are shown in Fig. 1. Despite the high temperature, the two most extreme evaporation residues reached the solidus during evaporation; the other residues with lower degrees of evaporation remained liquid until cooled at the end of the experiment. The most extreme residue consists largely of mixed Sc, Y and Zr oxides; most of the Ti and nearly all of the Ca have evaporated. In this residue, there are large depletions in Sr, Nb, Ba, Ce and Eu and smaller depletions of La, Pr, Nd, Sm and Yb compared to Sc, Zr and most heavy REE. There is, however, little fractionation of the heavy REE from one another. The chemical composition and even the physical state of the residues change with degree of evaporation, undoubtedly affecting evaporation rates of trace elements. For example, even though the experiments are all carried out at a single temperature and both Ce and Eu are quite depleted in the most extreme residue, Ce evaporates early and Eu evaporates late (Fig. 1). Ultrarefractory inclusions show substantial fractionations among the heavy REE that have been attributed to volatility fractionation [7]. Kinetically controlled evaporation produces large isotopic mass fractionation effects in Ca and Ti [6], whereas there is minimal isotopic fractionation between gas and condensed phases at high temperatures. The lack of large isotopic fractionation effects in ultrarefractory inclusions [7] suggests that these objects did not form by kinetically controlled evaporation. The residues we have produced have bulk chemical compositions consistent with ultrarefractory inclusions, as they are composed of mixed Sc, Zr and Y oxides, but they do not have as much heavy to light REE fractionation nor do they show the substantial fractionation among the heavy REE that is characteristic of ultrarefractory inclusions. This difference supports the idea that the volatility fractionations of trace elements observed CAIs are thermodynamically rather than kinetically controlled. References: [1] Tanaka T. and Masuda A. (1973) Icarus, 19, 523-530. [2] Boynton W. V. (1975) GCA, 39, 569-584. [3] Davis A. M. and Grossman L. (1979) GCA, 43, 1611-1632. [4] MacPherson G. J. and Davis A. M. (1994) GCA, 58, 5599-5625. [5] Wang J. et al. (1993) Meteoritics, 28, 454-455. [6] Davis A. M. et al. (1995) LPS XXVI, 317-318. [7] Davis A. M. (1991) Meteoritics, 26, 330. Fig. 1. Elemental enrichment factors in residues of initial stoichiometric CaTiO3 composition doped with 5% refractory trace elements in chondritic relative proportions, plotted in order of atomic number.

Davis, A. M.; Hashimoto, A.

1995-09-01

117

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

118

Siderophile element fractionation in meteor crater impact glasses and metallic spherules  

Microsoft Academic Search

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

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

1993-01-01

119

Rare earth element partitioning between hydrous ferric oxides and acid mine water during iron oxidation  

USGS Publications Warehouse

Ferrous iron rapidly oxidizes to Fe (III) and precipitates as hydrous Fe (III) oxides in acid mine waters. This study examines the effect of Fe precipitation on the rare earth element (REE) geochemistry of acid mine waters to determine the pH range over which REEs behave conservatively and the range over which attenuation and fractionation occur. Two field studies were designed to investigate REE attenuation during Fe oxidation in acidic, alpine surface waters. To complement these field studies, a suite of six acid mine waters with a pH range from 1.6 to 6.1 were collected and allowed to oxidize in the laboratory at ambient conditions to determine the partitioning of REEs during Fe oxidation and precipitation. Results from field experiments document that even with substantial Fe oxidation, the REEs remain dissolved in acid, sulfate waters with pH below 5.1. Between pH 5.1 and 6.6 the REEs partitioned to the solid phases in the water column, and heavy REEs were preferentially removed compared to light REEs. Laboratory experiments corroborated field data with the most solid-phase partitioning occurring in the waters with the highest pH. ?? 2004 Elsevier Ltd. All rights reserved.

Verplanck, P.L.; Nordstrom, D.K.; Taylor, H.E.; Kimball, B.A.

2004-01-01

120

Effects of Rare Earth Element Additions on the Impression Creep Behavior of AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

The effects of 1, 2, and 3 wt pct rare earth (RE) element additions on the microstructure and creep behavior of cast AZ91 Mg alloy were investigated by impression tests. The tests were carried out under constant punching stress in the range 200 to 650 MPa at temperatures in the range 425 to 525 K. Analysis of the data showed that for all loads and temperatures, the AZ91-2RE alloy had the lowest creep rates and, thus, the highest creep resistance among all materials tested. This is attributed to the formation of Al11RE3 with a branched morphology, reduction in the volume fraction of the eutectic ?-Mg17Al12 phase, and solid solution hardening effects of Al in the Mg matrix. The stress exponents and activation energies were the same for all alloy systems studied, 5.3 to 6.5 and 90 to 120 kJ mol-1, respectively, with the exception that the activation energy for the AZ91-3RE system was 102 to 126 kJ mol-1. An observed decreasing trend of creep-activation energy with stress suggests that two parallel mechanisms of lattice and pipe diffusion-controlled dislocation climb are competing. Dislocation climb controlled by dislocation pipe diffusion is controlling at high stresses, whereas climb of edge dislocations is the controlling mechanism at low stresses.

Kabirian, F.; Mahmudi, R.

2009-09-01

121

The leaching behaviour and geochemical fractionation of trace elements in hydraulically disposed weathered coal fly ash.  

PubMed

A five-step sequential extraction (SE) procedure was used to investigate the leaching behaviour and geochemical partitioning of the trace elements As, Zn, Pb, Ni, Mo, Cr and Cu in a 20-year-old fly ash (FA) dump. The weathered FA, which was hydraulically co-disposed with salt laden brine in slurry form (FA: brine ratio of 1:5), was analyzed and compared with fresh FA. The weathered FA samples were collected from three cores, drilled at a coal-fired power station in the Republic of South Africa while the fresh FA sample was collected from the hoppers in the ash collection system at the power station. The FA samples were sequentially leached using: ultrapure water; ammonium acetate buffer solution (pH 7); ammonium acetate buffer solution (pH 5); hydroxylamine hydrochloride in nitric acid (pH 2) and finally the residues were digested using a combination of HClO4: HF: HNO3 acids. Digestion of as received (unleached) FA samples was also done using a combination of HClO4: HF: HNO3 acids in order to determine the total metal content. The trace element analysis was done using ICP-OES (Varian 710-ES). The SE procedure revealed that the trace elements present in the fresh FA and the weathered FA samples obtained from the three cores could leach upon exposure to different environmental conditions. The trace elements showed continuous partitioning between five geochemical phases i.e., water soluble fraction, exchangeable fraction, carbonate fraction, Fe and Mn fraction and residual fraction. Although the highest concentration of the trace elements (ranging 65.51%-86.34%) was contained in the residual fraction, a considerable amount of each trace element (ranging 4.42%-27.43%) was released from the labile phases (water soluble, exchangeable and carbonate fractions), indicating that the trace species readily leach from the dumped FA under environmental conditions thus pose a danger to the receiving environment and to groundwater. PMID:24171424

Nyale, Sammy M; Eze, Chuks P; Akinyeye, Richard O; Gitari, Wilson M; Akinyemi, Segun A; Fatoba, Olanrewaju O; Petrik, Leslie F

2014-01-01

122

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 (mg kg(-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 (mg kg(-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

123

Rare earth element mobility in the Roffna Gneiss, Switzerland  

Microsoft Academic Search

The Roffna Gneiss, a deformed Hercynian granite porphyry within the Penninic nappes of eastern Switzerland, underwent extreme cataclasis with the progressive development of phengite towards the margins of the nappe under conditions of the glaucophane schist to greenschist facies. This resulted in the selective mobilization of major and trace elements over distances of 10's to 100's of meters and the

Robert D. Vocke; Gilbert N. Hanson; Marc Griinenfelder

1987-01-01

124

Fraction  

NSDL National Science Digital Library

These games are mostly for you to review. Start by practicing your fractions...in this game you will need to match the fraction to a picture Equivalent Fraction Click here in order to test your skills. You will get 4 different answers, it will be your job to save the bugs. Equivalent Fraction Click here to practice adding and subtraction using different denominators. Race ...

Castro, Ms.

2007-10-03

125

The variation of REE (rare earth elements) patterns in soil-grown plants: a new proxy for the source of rare earth elements and silicon in plants  

Microsoft Academic Search

Rare earth elements (REEs) in five species of soil-grown plants (Taxodium japonicum, Populus sieboldii, Sasa nipponica, Thea sinensis and Vicia villosa) and in the soil on which each plant grew were determined with an inductively coupled plasma mass spectrometer (ICP-MS) in order to observe the variation in the distribution of REEs and to elucidate their source in soil-grown plants. The

FengFu Fu; Tasuku Akagi; Sadayo Yabuki; Masaya Iwaki

2001-01-01

126

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

127

Empirical evidence for the fractionation of carbon isotopes between diamond and iron carbide from the Earth's mantle  

NASA Astrophysics Data System (ADS)

have studied two samples of mantle diamond containing iron carbide inclusions from Jagersfontein kimberlite, South Africa. Syngenetic crystal growth is inferred using morphological characteristics. These samples provide an opportunity to investigate the isotopic partitioning of 13C in a terrestrial natural high-pressure and high-temperature (HPHT) system. The difference for the ?13C values between the diamond and coexisting iron carbide averaged 7.2 ± 1.3‰. These data are consistent with available data from the literature showing iron carbide to be 13C-depleted relative to elemental carbon (i.e., diamond). We infer that the minerals formed by crystallization of diamond and iron carbide at HPHT in the mantle beneath the Kaapvaal Craton. It is unclear whether crystallization occurred in subcratonic or sublithospheric mantle; in addition, the source of the iron is also enigmatic. Nonetheless, textural coherence between diamond and iron carbide resulted in isotopic partitioning of 13C between these two phases. These data suggest that significant isotopic fractionation of 13C/12C (?13C up to >7‰) can occur at HPHT in the terrestrial diamond stability field. We note that under reducing conditions at or below the iron-iron wustite redox buffer in a cratonic or deep mantle environment in Earth, the cogenesis of carbide and diamond may produce reservoirs of 13C-depleted carbon that have conventionally been interpreted as crustal in origin. Finally, the large ?13C for diamond-iron carbide shown here demonstrates ?13C for silicate-metallic melts is a parameter that needs to be constrained to better determine the abundance of carbon within the Earth's metallic core.

Mikhail, S.; Guillermier, C.; Franchi, I. A.; Beard, A. D.; Crispin, K.; Verchovsky, A. B.; Jones, A. P.; Milledge, H. J.

2014-04-01

128

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry  

NASA Astrophysics Data System (ADS)

Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.

2014-09-01

129

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry  

NASA Astrophysics Data System (ADS)

Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.

2014-11-01

130

The Galerkin finite element method for a multi-term time-fractional diffusion equation  

NASA Astrophysics Data System (ADS)

We consider the initial/boundary value problem for a diffusion equation involving multiple time-fractional derivatives on a bounded convex polyhedral domain. We analyze a space semidiscrete scheme based on the standard Galerkin finite element method using continuous piecewise linear functions. Nearly optimal error estimates for both cases of initial data and inhomogeneous term are derived, which cover both smooth and nonsmooth data. Further we develop a fully discrete scheme based on a finite difference discretization of the time-fractional derivatives, and discuss its stability and error estimate. Extensive numerical experiments for one- and two-dimensional problems confirm the theoretical convergence rates.

Jin, Bangti; Lazarov, Raytcho; Liu, Yikan; Zhou, Zhi

2015-01-01

131

Development of Electronic Tongue for Detection of Rare Earth Elements in Natural Surroundings  

NASA Astrophysics Data System (ADS)

The rare earth elements (like lanthanum) and other metals like zirconium, arsenic, potassium, copper etc. are some of the elements, which are found in the natural surrounding. Since these metals have immense utility in the field of medical science, energy efficient electronic devices, nuclear energy domain, early and easy detection of such metals is very important. In the present work, voltammetric electronic tongue for detection and quantitative determination of these elements has been explored. A sensor array comprising of noble metals (like gold, iridium, rhodium etc) has been developed and it exhibits remarkable sensitivity and promising results for detection and analysis of these elements.

Sarkar, Subrata; Purkait, Monirul; Roy, Jayanta Kumar; Datta, C.; Bhattacharyya, Nabarun; Sarkar, D.; Datta, Jagannath; Chowdhury, D. P.

2011-09-01

132

Laser mass spectrometry of anomalous fractionation of isotopes of heavy elements  

SciTech Connect

The isotopic composition of the heavy elements Ti, Fe, Br, Sr, Ba, Nd, Gd, Dy, and Pb, contained in rock samples, on the sea bottom, and in sea shells, was measured by the method of laser mass spectrometry. The experimental data obtained are compared with the main characteristics of nuclear isotopes - spin, magnetic moment, electric quadrupole moment, and neutron binding energy. A correlation was observed between the combination of signs of the magnetic moment and electric quadrupole moment and the anomalous fractionation of isotopes of heavy elements. The behavior of protoisotopes and magic nuclei is studied.

Bykovskii, Yu.A.; Timoshin, V.T.; Laptev, N.D.; Manykin, E.A.

1988-07-01

133

Chemical fractionation of siderophile elements in impactites from Australian meteorite craters  

NASA Technical Reports Server (NTRS)

The abundance pattern of siderophile elements in terrestrial and lunar impact melt rocks was used extensively to infer the nature of the impacting projectiles. An implicit assumption made is that the siderophile abundance ratios of the projectiles are approximately preserved during mixing of the projectile constituents with the impact melts. As this mixture occurs during flow of strongly shocked materials at high temperatures, however there are grounds for suspecting that the underlying assumption is not always valid. In particular, fractionation of the melted and partly vaporized material of the projectile might be expected because of differences in volatility, solubility in silicate melts, and other characteristics of the constituent elements. Impactites from craters with associated meteorites offer special opportunities to test the assumptions on which projectile identifications are based and to study chemical fractionation that occurred during the impact process.

Attrep, A., Jr.; Orth, C. J.; Quintana, L. R.; Shoemaker, C. S.; Shoemaker, E. M.; Taylor, S. R.

1991-01-01

134

Authigenic phase formation and microbial activity control Zr, Hf, and rare earth element distributions in deep-sea brine sediments  

NASA Astrophysics Data System (ADS)

Sediments collected from hypersaline and anoxic deep-sea basins in the eastern Mediterranean (Thetis, Kryos, Medee, and Tyro) were characterised in terms of their mineralogical composition, the distributions of rare earth elements (REE), Zr, and Hf and their content of microbial DNA. We identified two major mineralogical fractions: one fraction of detritic origin was composed of quartz, gypsum, and low-Mg calcite bioclasts (with 0 < Mg < 0.07%) and another fraction of authigenic origin constituted of halite, dolomite, high-Mg calcite (with a Mg content of up to 22%) and rare bischofite and showed a textural evidence of microbial assemblages. We found that in the Medee and Tyro sediments, the shale-normalised REE pattern of these sediments is strongly enriched in middle REE (MREE), whereas in the Thetis and Tyro basins, a positive Gd anomaly in the residue was obtained after the removal of the water-soluble fraction. In all investigated basins, Y / Ho ratio clustered around chondritic values, whereas Zr / Hf ratio ranged from slightly subchondritic to superchondritic values. Subchondritic Y / Ho and Zr / Hf values were mainly found in the high-Mg carbonate having a microbial origin. The observed preferential removal of Zr with respect to Hf without significant partitioning of Y with respect to Ho indicates that the Zr / Hf ratio and Y-Ho fractionations are influenced by the microbial activity in the sediments. We propose that the concurrent Y-Ho and Zr-Hf fractionations are a suitable tracer of microbial activity in marine sediments.

Censi, P.; Saiano, F.; Zuddas, P.; Nicosia, A.; Mazzola, S.; Raso, M.

2014-02-01

135

Fractions.  

ERIC Educational Resources Information Center

An extensive investigation of pupil understanding of fractions at the secondary education level showed the majority tended to avoid using fractions, could not generalize about them, and probably did not see them as an extension of the set of whole numbers. (MP)

Hart, K.

1981-01-01

136

Imaging Earth's Interior based on Spectral-Element and Adjoint Methods (Invited)  

NASA Astrophysics Data System (ADS)

We use spectral-element and adjoint methods to iteratively improve 3D tomographic images of Earth's interior, ranging from global to continental to exploration scales. The spectral-element method, a high-order finite-element method with the advantage of a diagonal mass matrix, is used to accurately calculate three-component synthetic seismograms in a complex 3D Earth model. An adjoint method is used to numerically compute Frechét derivatives of a misfit function based on the interaction between the wavefield for a reference Earth model and a wavefield obtained by using time-reversed differences between data and synthetics at all receivers as simultaneous sources. In combination with gradient-based optimization methods, such as a preconditioned conjugate gradient or L-BSGF method, we are able to iteratively improve 3D images of Earth's interior and gradually minimize discrepancies between observed and simulated seismograms. Various misfit functions may be chosen to quantify these discrepancies, such as cross-correlation traveltime differences, frequency-dependent phase and amplitude anomalies as well as full-waveform differences. Various physical properties of the Earth are constrained based on this method, such as elastic wavespeeds, radial anisotropy, shear attenuation and impedance contrasts. We apply this method to study seismic inverse problems at various scales, from global- and continental-scale seismic tomography to exploration-scale full-waveform inversion.

Tromp, J.; Zhu, H.; Bozdag, E.

2013-12-01

137

Radioluminescence and thermoluminescence of rare earth element and phosphorus-doped zircon  

SciTech Connect

The radioluminescence and thermoluminescence spectra of synthetic zircon crystals doped with individual trivalent rare earth element (REE) ions (Pr, Sm, Eu, Gd, Dy, Ho, Er, and Yb) and P are reported in the temperature range 25 to 673 K. Although there is some intrinsic UV/blue emission from the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the REE{sup 3+} states. The shapes of the glow curves are different for each dopant, and there are distinct differences between glow peak temperatures for different rare-earth lines of the same element. Within the overall set of signals there are indications of linear trends in which some glow peak temperatures vary as a function of the ionic size of the rare earth ions. The temperature shifts of the peaks are considerable, up to 200{degree}, and much larger than those cited in other rare-earth-doped crystals of LaF{sub 3} and Bi{sub 4}Ge{sub 3}O{sub 12}. The data clearly suggest that the rare-earth ions are active both in the trapping and luminescence steps, and hence the TL occurs within localized defect complexes that include REE{sup 3+} ions.

Karali, T.; Can, N.; Townsend, P.D.; Rowlands, A.P.; Hanchar, J.M.

2000-06-01

138

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

139

Bulk and surface electronic structure of actinide, rare earth, and transition metal elements and compounds  

SciTech Connect

This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project sought to study of unusual magnetic and structural properties of rare earth, actinide, and transition metals through high-precision electronic structure calculations. Magnetic moment anisotropies in bulk and surface systems were studied, with emphasis on novel surfaces with unusual magnetic properties with possible applicability in magnetic recording. The structural stability, bonding properties, and elastic response of the actinides, as well as transition and rare earth elements and compounds, were also studied. The project sought to understand the unusual crystallographic and cohesive properties of the actinides and the importance of correlation to structural stability and the nature of the delocalization transition in these elements. Theoretical photoemission spectra, including surface effects, were calculated for rare earths and actinides.

Wills, J.W.; Eriksson, O.

1996-07-01

140

Rare earth element variations resulting from inversion of pigeonite and subsolidus reequilibration in lunar ferroan anorthosites  

Microsoft Academic Search

We present results of a secondary ion mass spectrometry study of the rare earth elements (REEs) in the minerals of two samples of lunar ferroan anorthosite, and the results are applicable to studies of REEs in all igneous rocks, no matter what their planet of origin. Our pyroxene analyses are used to determine solid-solid REE distribution coefficients (D = CREE

Odette B. James; Christine Floss; James J. McGee

2002-01-01

141

A LOW-COST RARE EARTH ELEMENTS RECOVERY TECHNOLOGY - PHASE I  

EPA Science Inventory

Physical Sciences, Inc., and the University of Kentucky Center for Applied Energy Research propose to develop a unique enabling technology to significantly reduce U.S. dependency for Rare Earth Elements (REE) on foreign suppliers and our global competitors. Our innovation...

142

Preprint of the paper "A Boundary Element Numerical Approach for Earthing Grid Computation"  

E-print Network

~na, SPAIN Abstract Analysis and design of substation earthing involves computing the equivalent re- sistance in the margin of error [4]. A Boundary Element approach for the numerical computation of substation grounding formulation has been implemented in a speci#12;c Computer Aided Design system for grounding analysis developed

Colominas, Ignasi

143

Interactions between exogenous rare earth elements and phosphorus leaching in packed soil columns  

Technology Transfer Automated Retrieval System (TEKTRAN)

Rare earth elements (REEs) increasingly used in agriculture as an amendment for crop growth may help to lessen environmental losses of phosphorus (P) from heavily fertilized soils. The vertical transport characteristics of P and REEs, lanthanum (La), neodymium (Nd), samarium (Sm), and cerium (Ce), w...

144

Studying the volatility of pyrazolone complexes of rare-earth elements by means of Knudsen effusion  

NASA Astrophysics Data System (ADS)

The temperature dependences of the pressure of saturated vapor of pyrazolone complexes of rare-earth elements Ln(PMIP)3 (where Ln = Y, Ho, Er, Tm, Lu; PMIP = 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone) are studied via Knudsen effusion, and the enthalpy of their sublimation is determined. Mass spectra and differential scanning calorimetry data are obtained.

Lazarev, N. M.; Petrov, B. I.; Bochkarev, L. N.; Safronova, A. V.; Abakumov, G. A.; Arapova, A. V.; Bessonova, Yu. A.

2014-08-01

145

Revisiting the rare earth elements in foraminiferal tests Brian A. Haley a,*, Gary P. Klinkhammer b  

E-print Network

Revisiting the rare earth elements in foraminiferal tests Brian A. Haley a,*, Gary P. Klinkhammer b of REEs in planktonic and benthic foraminifera. Several different cleaning protocols were tested. Although, it seems to remobilize metal oxides that are otherwise unaffected in flow-through dissolution

Kurapov, Alexander

146

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. PMID:22904278

Ochi, Kozo

2012-01-01

147

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-...

148

Tracing sediment movement on semi-arid watershed using Rare Earth Elements 1988  

Technology Transfer Automated Retrieval System (TEKTRAN)

A multi-tracer method employing rare earth elements (REE) was used to determine sediment yield and to track sediment movement in a small semiarid watershed. A 0.33 ha watershed near Tombstone, AZ was divided into five morphological units, each tagged with one of five REE oxides. Relative contributi...

149

Rare earth elements in garnets and clinopyroxenes from garnet lherzolite nodules in kimberlites  

Microsoft Academic Search

Six pairs of coexisting garnets and clinopyroxenes were separated from the sheared and granular garnet lherzolite nodules in kimberlites and analyzed for rare earth elements (REE). The sheared and granular nodules can be distinguished in terms of REE pattern of both clinopyroxene and garnet. However, there are no significant differences in REE partitioning between clinopyroxene and garnet, indicating that the

N. Shimizu

1975-01-01

150

Total photon attenuation coefficients in some rare earth elements using selective excitation method  

NASA Astrophysics Data System (ADS)

The total mass attenuation coefficients were measured in the elements La, Nd, Sm, Gd and Dy belonging to rare earth region in the energy range 30-55 keV by employing the selective excitation method. This method facilitates selection of excitation energies near the K edge. The present experimental results were compared with the theoretical values due to Chantler and XCOM.

SitaMahalakshmi, N. V.; Kareem, M. A.; Premachand, K.

2015-01-01

151

A semi-discrete finite element method for a class of time-fractional diffusion equations.  

PubMed

As fractional diffusion equations can describe the early breakthrough and the heavy-tail decay features observed in anomalous transport of contaminants in groundwater and porous soil, they have been commonly used in the related mathematical descriptions. These models usually involve long-time-range computation, which is a critical obstacle for their application; improvement of computational efficiency is of great significance. In this paper, a semi-discrete method is presented for solving a class of time-fractional diffusion equations that overcome the critical long-time-range computation problem. In the procedure, the spatial domain is discretized by the finite element method, which reduces the fractional diffusion equations to approximate fractional relaxation equations. As analytical solutions exist for the latter equations, the burden arising from long-time-range computation can effectively be minimized. To illustrate its efficiency and simplicity, four examples are presented. In addition, the method is used to solve the time-fractional advection-diffusion equation characterizing the bromide transport process in a fractured granite aquifer. The prediction closely agrees with the experimental data, and the heavy-tail decay of the anomalous transport process is well represented. PMID:23547234

Sun, HongGuang; Chen, Wen; Sze, K Y

2013-05-13

152

Chemical fractionation of radionuclides and stable elements in aquatic plants of the Yenisei River.  

PubMed

The Yenisei River is contaminated with artificial radionuclides released by one of the Russian nuclear plants. The aquatic plants growing in the radioactively contaminated parts of the river contain artificial radionuclides. The aim of the study was to investigate accumulation of artificial radionuclides and stable elements by submerged plants of the Yenisei River and estimate the strength of their binding to plant biomass by using a new sequential extraction scheme. The aquatic plants sampled were: Potamogeton lucens, Fontinalis antipyretica, and Batrachium kauffmanii. Gamma-spectrometric analysis of the samples of aquatic plants has revealed more than 20 radionuclides. We also investigated the chemical fractionation of radionuclides and stable elements in the biomass and rated radionuclides and stable elements based on their distribution in biomass. The greatest number of radionuclides strongly bound to biomass cell structures was found for Potamogeton lucens and the smallest for Batrachium kauffmanii. For Fontinalis antipyretica, the number of distribution patterns that were similar for both radioactive isotopes and their stable counterparts was greater than for the other studied species. The transuranic elements (239)Np and (241)Am were found in the intracellular fraction of the biomass, and this suggested their active accumulation by the plants. PMID:21815683

Bolsunovsky, Alexander

2011-09-01

153

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

154

Rare earth element evidence for the petrogenesis of the banded series of the Stillwater Complex, Montana, and its anorthosites  

USGS Publications Warehouse

A rare earth element (REE) study was made by isotope-dilution mass spectrometry of plagioclase separates from a variety of cumulates stratigraphically spanning the Banded series of the Stillwater Complex, Montana. Evaluation of parent liquid REE patterns, calculated on the basis of published plagioclase-liquid partition coefficients, shows that the range of REE ratios is too large to be attributable to fractionation of a single magma type. At least two different parental melts were present throughout the Banded series. This finding supports hypotheses of previous workers that the Stillwater Complex formed from two different parent magma types, designated the anorthosite- or A-type liquid and the ultramafic- or U-type liquid. -from Authors

Loferski, P.J.; Arculus, R.J.; Czamanske, G.K.

1994-01-01

155

Rare-earth elements in hot brines (165 to 190 degree C) from the Salton Sea geothermal field  

SciTech Connect

Rare-earth element (REE) concentrations are important indicators for revealing various chemical fractionation processes (water/rock interactions) and source region geochemistry. Since the REE patterns are characteristic of geologic materials (basalt, granite, shale, sediments, etc.) and minerals (K-feldspar, calcite, illite, epidote, etc.), their study in geothermal fluids may serve as a geothermometer. The REE study may also enable us to address the issue of groundwater mixing. In addition, the behavior of the REE can serve as analogs of the actinides in radioactive waste (e.g., neodymium is an analog of americium and curium). In this paper, the authors port the REE data for a Salton Sea Geothermal Field (SSGF) brine (two aliquots: port 4 at 165{degree}C and port 5 at 190{degree}C) and six associated core samples.

Lepel, E.A.; Laul, J.C.; Smith, M.R.

1988-01-01

156

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

157

Heavy metals and rare earth elements in phosphate fertilizer components using instrumental neutron activation analysis.  

PubMed

The technique of instrumental neutron activation analysis was applied as a sensitive nondestructive analytical tool for the determination of heavy metals and rare earth elements in phosphate fertilizer ingredients. The contents of heavy metals Fe, Zn, Co, Cr and Sc as well as rare earth elements La, Ce, Hf, Eu, Yb and Sm were determined in four samples representing the phosphate fertilizer components (e.g. rock phosphate, limestone and sulfur). These samples were collected from the Abu-Zabal phosphate factory in El-Qalubia governarate, Egypt. The aim of this study was to determine the elemental pattern in phosphate ingredients as well as in the produced phosphate fertilizer. Fair agreement was found between the results obtained for the standard reference material Soil-7 and the certified values reported by the International Atomic Energy Agency. The results for the input raw materials (rock phosphate, limestone and sulfur) and the output product as final fertilizer are presented and discussed. PMID:11545513

Abdel-Haleem, A S; Sroor, A; El-Bahi, S M; Zohny, E

2001-10-01

158

[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

159

Behaviour of zirconium, niobium, yttrium and the rare earth elements in the Thor Lake rare-metal  

E-print Network

Behaviour of zirconium, niobium, yttrium and the rare earth elements in the Thor Lake rare-metal © Emma Rebecca Sheard, 2010 #12;i ABSTRACT The Thor Lake rare-metal (Zr, Nb, Y, REE, Ta, Be, Ga) deposit and the heavy rare earth elements in the world. Much of the potentially economic mineralization was concentrated

160

Rare Earth Element sorption by basaltic rock: experimental data and modeling results using the "Generalised Composite approach".  

E-print Network

Rare Earth Element sorption by basaltic rock: experimental data and modeling results using Email address : emmanuel.tertre@univ-poitiers.fr Keywords: sorption, lanthanides, basalt, surface.1016/j.gca.2007.12.015 #12;Abstract Sorption of the 14 Rare Earth Elements (REE) by basaltic rock

Paris-Sud XI, Université de

161

Sulfur isotope fractionation during the reduction of elemental sulfur and thiosulfate by Dethiosulfovibrio spp.  

NASA Astrophysics Data System (ADS)

Thiosulfate and elemental sulfur are typical by-products of the oxidation of dissolved sulfide and important sulfur intermediates in the biogeochemical sulfur cycle of natural sediments where they can be further transformed by microbial or chemical oxidation, reduction, or disproportionation. Due to the often superimposing reaction pathways of the sulfur intermediates in natural environments specific tracers are needed to better resolve the complex microbial and biogeochemical reactions. An important fingerprint for sulfur cycling is provided by the microbial fractionation of the stable sulfur isotopes S-34 and S-32. Proper interpretation of isotope signals in nature, however, is only possible by the calibration with results obtained with pure cultures under defined experimental conditions. In addition, sulfur isotope discrimination may provide informations about specific encymatic biochemical pathways within the bacterial cells. In this study, we report the results for the discrimination of stable sulfur isotopes S-32 and S-34 during reduction of thiosulfate and elemental sulfur by non-sulfate, but sulfur- and thiosulfate-reducing bacteria which are phylogenetically not related to sulfate-reducing bacteria. Experiments with were conducted at known cell-specific thiosulfate reduction rates. Stable sulfur isotope fractionation was investigated during reduction of thiosulfate and elemental sulfur at 28°C by growing batch cultures of Dethiosulfovibrio marinus WS100 (type strain DSM 12537) and Dethiosulfovibrio russensis (type strain DSM 12538) using citrate as carbon and energy source. The cell-specific reduction rates were 0.3 to 2.4 fmol cell-1 d-1 (thiosulfate) and 31 to 38 fmol cell-1 d-1 (elemental sulphur), respectively. The sulfide produced was depleted in S-34 by 12 per mil compared to total thiosulfate sulfur, close to previous results observed for sulfate-reducing bacteria, indicating that the thiosulfate-reducing mechanism of sulfate reducers is similar to that of the investigated thiosulfate-reducing strains. Elemental sulfur reduction yields sulfide depleted in S-34 and isotope fractionation effects between 1.3 and 5.2 per mil for Dethiosulfovibrio russensis and 1.7 and 5.1 per mil Dethiosulfovibrio marinus, with the smaller fractionation effects observed in the exponential growth phase and enhanced discrimination under conditions of citrate depletion and cell lysis.

Surkov, A. V.; Böttcher, M. E.; Kuever, J.

2009-04-01

162

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

163

High contents of rare earth elements (REEs) in stream waters of a Cu–Pb–Zn mining area  

Microsoft Academic Search

Stream waters draining an old mining area present very high rare earth element (REE) contents, reaching 928 ?g\\/l as the maximum total value (?REE). The middle rare earth elements (MREEs) are usually enriched with respect to both the light (LREEs) and heavy (HREEs) elements of this group, producing a characteristic “roof-shaped” pattern of the shale Post-Archean Australian Shales-normalized concentrations. At

G Protano; F Riccobono

2002-01-01

164

Major and Trace Element Modeling of LREE-depleted Shergottites Via Fractional Crystallization from a Y980459-like Parent  

Microsoft Academic Search

Fractional crystallization models reproduce the major and trace element abundances of the LREE-depleted shergottites assuming a parent liquid similar to Y980459. These models suggest that assimilation of evolved crustal material is not required.

S. J. Symes; L. E. Borg; C. K. Shearer

2006-01-01

165

Behaviour of rare-earth elements during high-pressure metamorphism  

NASA Astrophysics Data System (ADS)

The behaviour of rare-earth elements (REE) during high-pressure metamorphism has been studied to estimate their possible use in determining the geodynamic settings of eclogite procoliths. Eclogites exhibiting various degrees of amphibolitization have been studied in a number lf metamorphic complexes in the Urals-Mongolian fold belt (the Kokchetav massif in northern Kazakhstan and the Atbashi range in the Central Tien-Shan, all in the U.S.S.R.). In addition, an eclogitized metagabbro from the Koralpe, Austrian Alps and gabbroids transformed into garnet amphibolites from the Kokhchetav massif have been investigated. The analytical data suggest that about 30-60% of the light rare-earth elements (LREE) in eclogites is present in the intergranular space. The results of the investigation demonstrate that the REE were virtually immobile during eclogite formation. Their low mobility can be explained either by absence of complex formers in the fluid phase or by low fluid/rock ratio.

Shatsky, V. S.; Kozmenko, O. A.; Sobolev, N. V.

1990-11-01

166

Symmetric charge-transfer cross sections of IIIa rare-earth-metal elements  

SciTech Connect

Symmetric charge-transfer cross sections of IIIa rare-earth-metal elements (Sc, Y, and Gd) in the impact energy range of 30 to 1000 eV were measured for the first time. The experiments were performed with a crossed-beam apparatus that featured primary ion production by photoionization with a tunable dye laser. Comparing the cross sections of IIIa rare-earth-metal elements ({sigma}{sub Sc}, {sigma}{sub Y}, and {sigma}{sub Gd}) with those of alkali metals or helium {sigma}{sub 0}, we found that {sigma}{sub 0{approx_equal}{sigma}Sc}<{sigma}{sub Y}<{sigma}{sub Gd{approx_equal}}2{sigma}{sub 0}at an impact energy of 1000 eV.

Hashida, Masaki; Sakabe, Shuji; Izawa, Yasukazu [ARCBS, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan) and Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502 (Japan); Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan) and Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2011-03-15

167

Surface Ionization of Some Rare Earth Elements on Hot Polycrystalline Tungsten Surface  

Microsoft Academic Search

The surface ionization of the rare earth elements Gd, Ho, Dy, Pr and Er has been studied for very low electric field (<3 KV\\/cm) at the surface and the ionization potentials (I.P.) of these elements have been measured. The values of ionization potentials are: Gd- 6.73± 0.09 eV, Ho- 6.08± 0.09 eV, Dy- 5.72± 0.10 eV, Pr- 5.61± 0.11 eV

S. D. Dey; S. B. Karmohapatro

1967-01-01

168

Rare earth elements in waters from the albitite-bearing granodiorites of Central Sardinia, Italy  

Microsoft Academic Search

With the aim of contributing to the knowledge of the geochemical behaviour and mobility of the rare earth element (REE) in the natural water systems, the ground and surface waters of the Ottana–Orani area (Central Sardinia, Italy) were sampled. The study area consists of albititic bodies included in Hercynian granodiorites. The waters have pH in the range of 6.0–8.6, total

Riccardo Biddau; Rosa Cidu; Franco Frau

2002-01-01

169

Fracture toughness improvement of austempered high silicon steel by titanium, vanadium and rare earth elements modification  

Microsoft Academic Search

The microstructure of austempered high silicon (AHS) steel before and after treating with a modifier containing titanium, vanadium and rare earth elements (so-called Ti–V–RE modifier) and austempered at different temperatures has been investigated. The plane strain fracture toughness of the steel in room temperature and ambient atmosphere has been examined. The microstructure was characterized using X-ray diffraction, scanning electron microscopy,

Xiang Chen; Yanxiang Li

2007-01-01

170

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

171

Heavy metals and rare earth elements (REEs) in soil from the Nam Co Basin, Tibetan Plateau  

Microsoft Academic Search

Twenty-eight soil samples collected from the Nam Co Basin, Tibetan Plateau, have been analyzed for heavy metals (Cd, Cr, Ni,\\u000a Cu, Zn, Pb and Mn), arsenic (As) and rare earth elements (REEs). In addition, for establishing the basic physio-chemical characteristics\\u000a of the soil, pH, total organic concentration, electrical conductivity, and effective cation exchange capacity were measured.\\u000a The results indicate that

Chaoliu Li; Shichang Kang; Xiaoping Wang; F. Ajmone-Marsan; Qianggong Zhang

2008-01-01

172

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

173

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

174

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

175

Highly siderophile elements in Earth's mantle as a clock for the Moon-forming impact.  

PubMed

According to the generally accepted scenario, the last giant impact on Earth formed the Moon and initiated the final phase of core formation by melting Earth's mantle. A key goal of geochemistry is to date this event, but different ages have been proposed. Some argue for an early Moon-forming event, approximately 30 million years (Myr) after the condensation of the first solids in the Solar System, whereas others claim a date later than 50?Myr (and possibly as late as around 100?Myr) after condensation. Here we show that a Moon-forming event at 40?Myr after condensation, or earlier, is ruled out at a 99.9 per cent confidence level. We use a large number of N-body simulations to demonstrate a relationship between the time of the last giant impact on an Earth-like planet and the amount of mass subsequently added during the era known as Late Accretion. As the last giant impact is delayed, the late-accreted mass decreases in a predictable fashion. This relationship exists within both the classical scenario and the Grand Tack scenario of terrestrial planet formation, and holds across a wide range of disk conditions. The concentration of highly siderophile elements (HSEs) in Earth's mantle constrains the mass of chondritic material added to Earth during Late Accretion. Using HSE abundance measurements, we determine a Moon-formation age of 95?±?32?Myr after condensation. The possibility exists that some late projectiles were differentiated and left an incomplete HSE record in Earth's mantle. Even in this case, various isotopic constraints strongly suggest that the late-accreted mass did not exceed 1 per cent of Earth's mass, and so the HSE clock still robustly limits the timing of the Moon-forming event to significantly later than 40?Myr after condensation. PMID:24695310

Jacobson, Seth A; Morbidelli, Alessandro; Raymond, Sean N; O'Brien, David P; Walsh, Kevin J; Rubie, David C

2014-04-01

176

Sorption of Yttrium and the Rare Earth Elements on Non-Living Macroalgal Tissue  

NASA Astrophysics Data System (ADS)

We have investigated sorption of yttrium and the rare earth elements (YREEs) on tissue of the green macroalga Ulva lactuca, commonly known as sea lettuce. Due to its nearly worldwide distribution in coastal waters, very simple morphology, and prodigious capacity for trace metal uptake from seawater, members of the Ulva genus serve as a basic but representative model of marine organic substrates in this type of study. In order to exclude active biological uptake effects, allowing us to focus on passive chemical mechanisms, we performed our initial experiments with sea lettuce Certified Reference Material consisting of a dehydrated, powdered tissue homogenate. A small quantity of this powder was suspended in NaCl solutions containing all YREEs, except Pm, at pH 3 and T = 25°C. The extent of YREE sorption was determined as a function of pH at constant temperature by titrating the solution with dilute NaOH and measuring the YREE concentrations of 0.2-?m filtered aliquots with an ICP-MS at regular time intervals after each pH adjustment. In NaCl solutions with an ionic strength approaching that of seawater, distribution coefficients, which quantify the proportion of sorbed and dissolved metal concentrations, are a highly linear function of pH in the range 3-8. The slope of the line suggests a sorption mechanism that involves ion exchange with both H+ and Na+ on surface functional groups. The shape of solution YREE patterns indicates that these functional groups are probably carboxylates at low and intermediate pH, but that other groups may contribute at high pH. The identification of carboxylate functional groups appears to be confirmed by preliminary results from EXAFS spectroscopic analyses of individual REE sorbed on the surface of Ulva lactuca tissue under similar conditions, conducted at the ANL Advanced Photon Source. In dilute NaCl solutions the distribution coefficient is largely independent of pH. We believe that prolonged exposure of the tissue to a low ionic strength solution may modify the chemical structure of the cell wall and make it permeable to organic ligands that otherwise sequester the YREEs in the cell interior. Chemical extraction of filtered solutions from the low ionic strength experiment with silica-bonded C18, showing that a substantial fraction of dissolved YREEs is distinctly hydrophobic, seems to support this hypothesis. Additional experiments to clarify these observations, including acid-base titrations of the Ulva lactuca tissue to assess the number of different functional groups and their surface densities, are currently ongoing.

Schijf, J.; Straka, A. M.

2007-12-01

177

Fractionation of Platinum Group Elements is not controlled by sulfide/silicate partition coefficients  

NASA Astrophysics Data System (ADS)

The distribution of PGEs between mantle and basaltic melt is well known but poorly understood. The fertile mantle has PGE concentrations of about 0.7 percent of the chondritic values, and the PGE ratios are chondritic (McDonough and Sun, 1995, Chem. Geol. 120, 223--253). In primitive basalts the PGEs are strongly fractionated from each other such that the refractory elements (Os, Ir, Ru) are depleted relative to the less refractory PGEs (Rh, Pt, Pd). We report piston cylinder experiments to understand the physical behaviour of sulfide during partial melting. Fertile mantle material was prepared from finely ground natural mineral separates, doped with different amounts of Fe-Ni-Cu sulfide, and melted in a piston cylinder apparatus at 1350^oC and 0.5 GPa. Nearly all sulfide collects as droplets immersed in interstitial silicate melt pockets at grain boundaries. Droplet sizes are small enough to be washed out of the matrix as "accidental sulfide fraction" when the silicate melt segregates from the matrix. It is the PGE budget of this accidental sulfide fraction that later dominates the absolute PGE content of a basalt at the surface. Our experimental results also indicate that the solidus of monosulfide lies above the solidus of dry, fertile mantle. This implies that crystalline monosulfide solid solution is a stable phase in partially molten upper mantle. The observed PGE ratios in primitive basalts therefore reflect the partitioning of PGEs between monosulfide solid solution and sulfide liquid (Ballhaus et al., 2001, J. Petrol. 42, 1911--1926). During melt segregation, Os, Ir, and Ru remain in the mantle source with the solid residual sulfide, whereas Pt and Pd are washed out along with the accidental sulfide fraction. Neither the absolute nor the relative PGE abundances in basalts are governed by sulfide/silicate partition coefficients.

Bockrath, C.; Holzheid, A.; Ballhaus, C.

2003-04-01

178

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. PMID:19001263

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

2008-01-01

179

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

NASA Astrophysics Data System (ADS)

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 ( Rp) to the gross forward precipitation rate ( Rf), for conditions where ionic transport to the growing crystal surface is not rate-limiting. The value of Rp has been experimentally measured under varying conditions, but the magnitude of Rf 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, Rf can be estimated from the bulk far-from-equilibrium dissolution rate of calcite ( Rb or kb), since at equilibrium Rf = Rb, and Rp = 0. Hence it can be inferred that Rf ? Rp + Rb. 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 Rp (= Rf - Rb) ? Rb. For precipitation rates high enough that Rp ? Rb, 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 Rp ? Rb for Ca isotopic fractionation. According to this model, Ca isotopic data can be used to estimate Rf 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 Rp. Allowing Rb to vary as Rp1/2, consistent with available precipitation rate studies, produces a better fit to some trace element and isotopic data than a model where Rb is constant. This model can account for most of the experimental data in the literature on the dependence of 44Ca/ 40Ca and metal/Ca fractionation in calcite as a function of precipitation rate and temperature, and also accounts for 18O/ 16O variations with some assumptions. The apparent temperature dependence of Ca isotope fractionation in calcite may stem from the dependence of Rb 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 require hyper-fast diffusivity in near-surface layers of the solid.

DePaolo, Donald J.

2011-02-01

180

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

181

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

NASA Astrophysics Data System (ADS)

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.

1983-07-01

182

Preliminary phytochemical and elemental analysis of aqueous and fractionated pod extracts of Acacia nilotica (Thorn mimosa)  

PubMed Central

Acacia nilotica (Thorn mimosa) is used locally for various medicinal purposes by traditionalists and herbalists in northeastern Nigeria. Plants products have been used since ancient times in the management of various conditions. The bark of A. nilotica has been reported to be used traditionally to manage diabetes, dysentery, leprosy, ulcers, cancers, tumor of the eye, ear and testicles, induration of liver and spleen and also in treatment of various condylomas. The objective of this study is to determine the phytochemical and elemental constituents of the extracts of A. nilotica pods. Flame emission and atomic absorption spectrometry were also used to determine the presence or absence of micro- and macro-elements in the extracts. Phytochemical analysis of the aqueous, ethyl acetate and N-butanol fractionated portions of the pod extracts of A. nilotica revealed the presence of tannins, saponins, flavonoids, carbohydrate, whereas carbohydrates and tannins were the only constituent in the residue portion. Anthraquinones, alkaloids, terpene and steroids were not present in the extracts. The elemental screening revealed the presence of iron, potassium, manganese, zinc, calcium, phosphorous, magnesium, sodium, cadmium and copper. Lead, arsenic and molybdenum were not detected in the pod. PMID:25568701

Auwal, Mohammed Shaibu; Saka, Sanni; Mairiga, Ismail Alhaji; Sanda, Kyari Abba; Shuaibu, Abdullahi; Ibrahim, Amina

2014-01-01

183

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

184

Complementary rare earth element patterns in unique achondrites, such as ALHA 77005 and shergottites, and in the earth  

NASA Technical Reports Server (NTRS)

Abundances of major, minor, and trace elements are determined in the Antarctic achondrite Allan Hills (ALHA) 77005 via sequential instrumental and radiochemical neutron activation analysis. The rare earth element (REE) abundances of ALHA 77005 reveal a unique chondritic normalized pattern; that is, the REEs are nearly unfractionated from La to Pr at approximately 1.0X chondrites, monotonically increased from Pr to Gd at approximately 3.4X with no Eu anomaly, nearly unfractionated from Gd and Ho and monotonically decreased from Ho to Lu at approximately 2.2X. It is noted that this unique REE pattern of ALHA 77005 can be modeled by a melting process involving a continuous melting and progressive partial removal of melt from a light REE enriched source material. In a model of this type, ALHA 77005 could represent either a crystallized cumulate from such a melt or the residual source material. Calculations show that the parent liquids for the shergottites could also be derived from a light REE enriched source material similar to that for ALHA 77005.

Ma, M.-S.; Schmitt, R. A.; Laul, J. C.

1982-01-01

185

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

186

Effects of rare earth elements substitution for Ti on the structure and electrochemical properties of a Fe-doped Ti–V-based hydrogen storage alloy  

Microsoft Academic Search

Effects of a partial substitution of rare-earth elements of Y, La, Ce, Pr, Nd in an atom fraction of 1\\/8 for Ti on the structure and electrochemical property of a Fe-doped Ti–V-based hydrogen storage alloy, Ti0.8Zr0.2V2.7Mn0.5Cr0.6Ni1.25Fe0.2, have been investigated systematically using X-ray diffraction, scanning electron microscope, energy dispersive spectroscope and electrochemical tests including charge\\/discharge, high rate dischargeability, polarization, etc. The

Mingxia Gao; He Miao; Yu Zhao; Yongfeng Liu; Hongge Pan

2009-01-01

187

Alkylation of isobutane with butenes in the presence of HNaY zeolite modified by cations of nickel, calcium and rare-earth elements  

SciTech Connect

A study was made of alkylation of isobutane with n-butenes in the presence of ion-exchange forms of zeolites, containing ions of Ni/sup 2 +/ and rare-earth elements. It was established that the addition to HCaY zeolite of Ni/sup 2 +/ ions reduces alkylate yield and increases the content of intermediate products. The use in the reaction studied of HCaY zeolite containing La/sup 3 +/ or Gd/sup 3 +/ ions increases the content of iso-octane hydrocarbons in the alkylate and reduces the content of fractions C/sub 9/ and higher.

Kuznetsov, O.I.; Panchenkov, G.M.; Plakhotnik, V.A.; Razali, B.; Tolkacheva, Y.I.

1981-01-01

188

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

189

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

190

NEW RARE EARTH ELEMENT ABUNDANCE DISTRIBUTIONS FOR THE SUN AND FIVE r-PROCESS-RICH VERY METAL-POOR STARS  

SciTech Connect

We have derived new abundances of the rare earth elements Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five elements are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other elements in individual stars, to produce internally consistent Ba, rare earth, and Hf (56 {<=} Z {<=} 72) element distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.

Sneden, Christopher [Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712 (United States); Lawler, James E.; Den Hartog, Elizabeth A. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Cowan, John J. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Ivans, Inese I. [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States)], E-mail: chris@verdi.as.utexas.edu, E-mail: jelawler@wisc.edu, E-mail: eadenhar@wisc.edu, E-mail: cowan@nhn.ou.edu, E-mail: iii@ociw.edu

2009-05-15

191

New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars  

E-print Network

We have derived new abundances of the rare-earth elements Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five elements are in good agreement with meteoritic abundances. For the low metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other elements in individual stars, to produce internally-consistent Ba, rare-earth, and Hf (56<= Z <= 72) element distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.

Sneden, Christopher; Cowan, John J; Ivans, Inese I; Hartog, Elizabeth A Den

2009-01-01

192

Trace-Element Analysis of Metal Nodules, Magnetic and Nonmagnetic Fractions, and Chondrules of the Qingzhen EH3 Chondrite  

NASA Astrophysics Data System (ADS)

The contents of Na, Sc, Cr, Mn, Fe, Co, Ni, Zn, Ga, As, Se, Br, Sb, W, Ir, and Au in metallic nodules, magnetic and nonmagnetic fractions, and chondrules of the Qingzhen EH3 chondrite have been determined by instrumental neutron activation analysis (INAA). Five of the largest separated chondrules (0.07- 5.77 mg) were selected for INAA. After extraction of the chondrules, the residual sample was gently ground to reduce the grain size and sieved into the following fractions: >500 micrometers, 200-500 micrometers, 100-200 micrometers, 50-100 micrometers, 15-50 micrometers, and <15 micrometers. All fractions were separated by a hand magnet into a nonmagnetic fraction, consisting mainly of silicates and sulfides (mainly troilite), and a magnetic fraction consisting of metal, sulfide, and minor silicates. The separated magnetic nodules from the >500-micrometer fraction weighed between 0.49 mg and 3.99 mg. From all the powders, aliquots of 10 mg were irradiated at the German Cancer Research Institute at Heidelberg (TRIGA-HD II) and counted by using a large-volume, high-resolution Ge(Li) detector. In every irradiation step two samples of the Allende chondrite acted as primary standards. Results: Element concentrations vary with the grain size of the metal due to kamacite in the coarse and schreibersite +- perryite in the intermediate and fine fractions. The element contents (normalized to Fe) of Na, Sc, Cr, Mn, Ni, Se, W, Ir, and Au increase in the metal with decreasing grain size. Cobalt and As display a trend opposite to that of Ni and Au, decreasing with decreasing grain size of the metal in Qingzhen. Whereas the abundance ratios (relative to CI chondrites) of As, Au, and Co are very similar, the refractory siderophile elements Ir and W are depleted in the metal. Under high reducing conditions Ir and W belong to the most refractory siderophiles. The depletion of the refractory elements in Qingzhen with respect to carbonaceous chondrites has been attributed to a partial loss of an early condensate and of a minor metallic phase rich in Ir and W. The W/Ir ratio of the host materials was greater than the ratio in carbonaceous chondrites. This difference in element/Ni ratios observed in Qingzhen metal can be attributed to a loss of refractory-rich material at high temperatures, before Ni and Au had completely condensed. The constancy of the ratios of Ni/Au and As/Co suggests that these elements were not fractionated during the metal-silicate fractionation process and their ratios were already established prior to the loss of metal. This implies that the above elements were already condensed when the fractionation process took place. Because of its lithophile character at low temperature, W was already partly oxidized at the time of the separation of metal from silicates and fractionated. A fractionation of the elements took place before the formation of Qingzhen metal and W was separated as an oxide in an oxidizing environment. The chemical composition of Qingzhen shows that the chondritic material was fractionated in two processes before accretion of the parent body: (1) fractionation of refractory elements under relatively high oxidation conditions and (2) a metal-silicate fractionation. The first process was earlier and has been attributed to the depletion of the high-temperature condensates and a metallic component enriched in the refractory siderophile elements Ir and W. The second fractionation process took place below the condensation temperature of Fe-Ni metal.

Schmidt, G.; Pernicka, E.

1993-07-01

193

The geochemistry of rare earth elements in the seasonally anoxic water column and porewaters of Chesapeake Bay  

NASA Astrophysics Data System (ADS)

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 is on the coupling between REDOX (Reduction-Oxidation) variations and REE cycling, fractionation of trivalent REEs and development of cerium anomalies. The time-series results demonstrate that REEs have large seasonal cycles in both the water column and porewaters in response to the development of anoxia in the spring and reoxygenation in the fall. The transition from oxic to suboxic to anoxic conditions results in the release of REEs into the upper porewaters and bottom waters. The release of REEs and Fe are coincident in the bottom waters, while the release of REEs lags Fe by approximately 50 days in the upper porewaters. This decoupling is explained in terms of a REDOX front which moves upward from the sediments to bottom waters during the development of seasonal anoxia. The release of REEs to the upper porewaters and bottom water are accompanied by (1) fractionation across the trivalent REE series and by (2) the preferential input of Ce relative to its trivalent-only REE neighbors. REE (III) fractionation is such that the relative rate of release increases from Lu to La (light REE > middleREE > heavyREE). During reoxygenation, removal of dissolved REEs occurs from both the water column and upper porewaters and follows the same relative rates, LREE > MREE > HREE. Cerium removal occurs faster than its neighbor REE(III), indicating a rapid oxidation of Ce(III) to Ce(IV).

Sholkovitz, E. R.; Shaw, T. J.; Schneider, D. L.

1992-09-01

194

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

195

Determination of Trace Rare Earth Elements in Plant and Soil Samples by Inductively Coupled Plasma-Mass Spectrometry  

Microsoft Academic Search

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of rare earth elements (REEs) in plants and soils. Sample preparation and analytical conditions were investigated to set up a simple routine procedure for measuring rare earth elements. For prompt sample decomposition, a microwave digestion technique was successfully used with an acid mixture of HCl+HNO3+HF. Detection limits, reproducibility, accuracy

Xinde Cao; Ying Chen; Zhimang Gu; Xiaorong Wang

2000-01-01

196

Numerical analysis of an H1-Galerkin mixed finite element method for time fractional telegraph equation.  

PubMed

We discuss and analyze an H(1)-Galerkin mixed finite element (H(1)-GMFE) method to look for the numerical solution of time fractional telegraph equation. We introduce an auxiliary variable to reduce the original equation into lower-order coupled equations and then formulate an H(1)-GMFE scheme with two important variables. We discretize the Caputo time fractional derivatives using the finite difference methods and approximate the spatial direction by applying the H(1)-GMFE method. Based on the discussion on the theoretical error analysis in L(2)-norm for the scalar unknown and its gradient in one dimensional case, we obtain the optimal order of convergence in space-time direction. Further, we also derive the optimal error results for the scalar unknown in H(1)-norm. Moreover, we derive and analyze the stability of H(1)-GMFE scheme and give the results of a priori error estimates in two- or three-dimensional cases. In order to verify our theoretical analysis, we give some results of numerical calculation by using the Matlab procedure. PMID:25184148

Wang, Jinfeng; Zhao, Meng; Zhang, Min; Liu, Yang; Li, Hong

2014-01-01

197

Numerical Analysis of an H1-Galerkin Mixed Finite Element Method for Time Fractional Telegraph Equation  

PubMed Central

We discuss and analyze an H1-Galerkin mixed finite element (H1-GMFE) method to look for the numerical solution of time fractional telegraph equation. We introduce an auxiliary variable to reduce the original equation into lower-order coupled equations and then formulate an H1-GMFE scheme with two important variables. We discretize the Caputo time fractional derivatives using the finite difference methods and approximate the spatial direction by applying the H1-GMFE method. Based on the discussion on the theoretical error analysis in L2-norm for the scalar unknown and its gradient in one dimensional case, we obtain the optimal order of convergence in space-time direction. Further, we also derive the optimal error results for the scalar unknown in H1-norm. Moreover, we derive and analyze the stability of H1-GMFE scheme and give the results of a priori error estimates in two- or three-dimensional cases. In order to verify our theoretical analysis, we give some results of numerical calculation by using the Matlab procedure. PMID:25184148

Wang, Jinfeng; Zhao, Meng; Zhang, Min; Liu, Yang; Li, Hong

2014-01-01

198

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

199

Partitioning of rare earth elements, yttrium, and some major elements among source rocks, liquid and vapor of Larderello-Travale geothermal field, Tuscany (Central Italy)  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE), yttrium and some major element concentrations have been measured in the high-enthalpy fluids (HEF) of several geothermal wells and the fluid's source rocks in the Larderello-Travale area (Tuscany/Central Italy). The REE and Y abundances in the HEF range from 0.1 to about 10 pmol/kg and are slightly higher in the HEF originating from evaporite/carbonate sequences (Calcare Cavernoso) than in those from phyllites. The resulting REY distribution factors between HEF and source rocks, appKdsource-rockHEF defined as the ratios of REY/Ca in both phases, range from <0.01 to 0.03 and 0.03 to 0.1 for phyllites and evaporite-limestone sequences (Calcare Cavernoso), respectively. REE+Y are more retained by the source rocks than Ca. HEF show no inherited and, with exception of a small Y anomaly, no acquired anomalies. This indicates a static equilibrium between HEF and the source rocks. The absence of any Eu anomalies points to temperatures less than 250°C in the source region. The small negative Y anomalies are the result of Y depletion in the rock fractions taking part in the water-rock interaction. Due to depressurization of the HEF to about 120°C and 2 bars, a liquid and a vapor phase is produced, which were sampled for the determination of the REE+Y partitioning between the two phases. The apparent partition factors between vapor and liquid appDliquidvapor of REE+Y range between 0.05 to 0.2 and about 3 for HEF originating from the phyllites and evaporites/carbonates, respectively. Among all ionic species determined, only NH 4+ has an apparent partition factor appDliquidvapor above one. In general, REY partition more easily into the vapor phase than the earth alkaline and alkaline elements. No significant correlation of REE+Y in the vapor phase with any of the determined ionic species could be detected. This probably points to the dominant presence of ion pairing such as REY(OH) 3o or REYO(OH) o.

Möller, P.; Dulski, P.; Morteani, G.

2003-01-01

200

The chemistry of the light rare-earth elements as determined by electron energy loss spectroscopy  

SciTech Connect

The energy loss spectra of the rare earths are characterized by sharp {ital M}{sub 4,5} edges, the relative intensities of which are characteristic of the 4{ital f}-shell occupancy of the excited ion. For the light rare earths, the dependence of these relative peak heights on 4{ital f}-shell occupancy is quite pronounced. Thus they may be used to determine the oxidation state of the multivalent elements Ce and Pr. The second derivative of the spectrum is shown to be extremely sensitive to the chemical environment. Modern instrumentation and detection techniques allow the oxidation state of Ce and Pr to be determined even when they are present as only minor constituents. {copyright} {ital 1996 American Institute of Physics.}

Fortner, J.A.; Buck, E.C. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)] [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

1996-06-01

201

Rare earth element partitioning between minerals from anhydrous spinel peridotite xenoliths  

NASA Astrophysics Data System (ADS)

REE abundances in minerals from spinel peridotite xenoliths from West Germany, the south-western U.S. and Mongolia decrease in the order clinopyroxene > orthopyroxene > olivine > spinel. While clinopyroxenes are similar in absolute chondrite-normalized concentrations to those known from other studies, orthopyroxenes and olivines are significantly lower in LREE although comparable in HREE. Spinels are much lower in all REE than any previously reported values and are completely negligible for the REE budget of peridotites. Partition coefficients for most orthopyroxene/clinopyroxene pairs increase systematically from La to Lu. Olivine/clinopyroxene and spinel/clinopyroxene partition coefficients increase from the intermediate rare earth elements to Lu and normally are higher for La compared to Sm. The application of Nagasawa's (1966) elastic lattice model suggests that all heavy but only minor amounts of the light REE substitute into structural positions of orthopyroxene and olivine. Significant differences between orthopyroxene/clinopyroxene partition coefficients for various xenoliths may be assigned to dependences upon equilibration temperature and bulk chemistry. Apart from grain surface contaminations, fluid inclusions which are practically always present in mantle minerals, can highly concentrate light rare earth elements and thus may be responsible for unexpectedly high concentrations of incompatible elements frequently reported for mantle olivines or orthopyroxenes.

Stosch, Heinz-Günter

1982-05-01

202

On the origin of falling-tone chorus elements in Earth's inner magnetosphere  

NASA Astrophysics Data System (ADS)

Generation of extremely/very low frequency (ELF/VLF) chorus waves in Earth's inner magnetosphere has received increased attention recently because of their significance for radiation belt dynamics. Though past theoretical and numerical models have demonstrated how rising-tone chorus elements are produced, falling-tone chorus element generation has yet to be explained. Our new model proposes that weak-amplitude falling-tone chorus elements can be generated by magnetospheric reflection of rising-tone elements. Using ray tracing in a realistic plasma model of the inner magnetosphere, we demonstrate that rising-tone elements originating at the magnetic equator propagate to higher latitudes. Upon reflection there, they propagate to lower L-shells and turn into oblique falling tones of reduced power, frequency, and bandwidth relative to their progenitor rising tones. Our results are in good agreement with comprehensive statistical studies of such waves, notably using magnetic field measurements from THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. Thus, we conclude that the proposed mechanism can be responsible for the generation of weak-amplitude falling-tone chorus emissions.

Breuillard, H.; Agapitov, O.; Artemyev, A.; Krasnoselskikh, V.; Le Contel, O.; Cully, C. M.; Angelopoulos, V.; Zaliznyak, Y.; Rolland, G.

2014-12-01

203

Luminescence and structural properties of RbGdS2 compounds doped by rare earth elements  

NASA Astrophysics Data System (ADS)

Rare earth elements (Pr, Ce) doped ternary sulfides of formula RbGd1-xRExS2 were synthesized in the form of crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. The X-ray powder diffraction detected only a single crystalline phase of rhombohedral lattice system. Optical properties of studied systems are investigated by methods of time-resolved luminescence spectroscopy. Thermal stability of the Pr3+ emission is demonstrated. Application potential in the white light-emitting diode solid state lighting or X-ray phosphors is discussed.

Jarý, V.; Havlák, L.; Bárta, J.; Mihóková, E.; Nikl, M.

2013-04-01

204

Extractive separation of alkaline-earth elements in the determination of lithium in brines  

SciTech Connect

The aim of this work was to investigate the possibility of using D2EHDTPA and D2EHPA to separate lithium from alkaline-earth elements, with subsequent determination of the lithium in the aqueous phase by the flame-photometric method. Extractive purification makes it possible to lower by an order of magnitude, in comparison to the direct method, the limit of detection of lithium in calcium chloride brines, and also to determine lithium in strontium compounds. The relative standard deviations in the determination of lithium by the method which has been developed do not exceed 0.05.

Shatskaya, S.S.; Samoilov, Yu.M.

1987-07-20

205

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

206

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

207

Effects of rare earth elements and REE-binding proteins on physiological responses in plants.  

PubMed

Rare earth elements (REEs), which include 17 elements in the periodic table, share chemical properties related to a similar external electronic configuration. REEs enriched fertilizers have been used in China since the 1980s. REEs could enter the cell and cell organelles, influence plant growth, and mainly be bound with the biological macromolecules. REE-binding proteins have been found in some plants. In addition, the chlorophyll activities and photosynthetic rate can be regulated by REEs. REEs could promote the protective function of cell membrane and enhance the plant resistance capability to stress produced by environmental factors, and affect the plant physiological mechanism by regulating the Ca²? level in the plant cells. The focus of present review is to describe how REEs and REE-binding proteins participate in the physiological responses in plants. PMID:21838699

Liu, Dongwu; Wang, Xue; Chen, Zhiwei

2012-02-01

208

Geochemistry of rare earth elements in Permian coals from the Huaibei Coalfield, China  

USGS Publications Warehouse

The rare earth elements (REEs) in coals are important because of: (a) REE patterns can be an indicator of the nature of source rocks of the mineral matter as well as sedimentary environments; (b) REEs abundance in coal may have industrial-significance. In this study, a total of thirty-four samples of Permian coal, partings, roof, and floor were collected from the Huaibei Coalfield, Anhui Province, China. Abundances of rare earth elements (REEs) and other elements in the samples were determined by inductively coupled-plasma mass spectrometry (ICP-MS) and inductively coupled-plasma atomic emission spectrometry (ICP-AES). The results show that the REEs are enriched in coals in the Huaibei Coalfield as compared with Chinese and U.S. coals and the world coal average. Coals in the Lower Shihezi Formation (No. 7, 5, and 4 Coals) and Upper Shihezi Formation (No. 3) have higher REE abundances than the coals in Shanxi Formation (No. 10). Magmatic intrusion resulted in high enrichment of REEs concentrations in No. 5 and 7 Coals. The REE abundances are positively correlated with the ash content. The mineral matter in these coals is mainly made up of clay minerals and carbonates. The REEs are positively correlated with lithophile elements including Si, Al, Ti, Fe, and Na, which are mainly distributed in clay minerals, indicating that REEs are contained mainly in clay minerals. The REE abundances in coals normalized by the ash are higher than that in partings. REEs abundances of coals cannot be accounted for by the REE content in the mineral matter, and some REEs associated with organic matter in coals. ?? 2007 Elsevier Ltd. All rights reserved.

Zheng, L.; Liu, G.; Chou, C.-L.; Qi, C.; Zhang, Y.

2007-01-01

209

Sample Preparation for Determination of Rare Earth Elements in Geological Samples by ICP-MS: A Critical Review  

Microsoft Academic Search

The presence of rare earth elements (REE) in geological materials provides important information about the formation and the geochemical processes suffered by the rocks. Therefore, there is a constant necessity for accurate data and reliable and fast analytical methods. However, the low concentrations of these elements typically found in rocks require quantification by sufficiently sensitive techniques, such as Inductively Coupled

Frederico Garcia Pinto; Rainério Escalfoni Junior; Tatiana Dillenburg SaintPierre

2012-01-01

210

Earth  

NASA Technical Reports Server (NTRS)

The following aspects of the planet Earth are discussed: plate tectonics, the interior of the planet, the formation of the Earth, and the evolution of the atmosphere and hydrosphere. The Earth's crust, mantle, and core are examined along with the bulk composition of the planet.

Carr, M. H.

1984-01-01

211

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

212

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

USGS Publications Warehouse

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 are depleted in light REEs (LREEs) and which show negative anomalies for YSN, and positive anomalies for LaSN, EuSN, GdSN, and in most cases, CeSN. They show considerably smaller Y/ Ho ratios than seawater or common igneous and clastic rocks, indicating that Y and Ho are fractionated in the marine environment. Compared to P-poor crusts, REYSN patterns of phosphatized Fe-Mn crusts are similar, but yield pronounced positive YSN anomalies, stronger positive LaSN anomalies, and enrichment of the HREEs relative to the MREEs. The data suggest modification of REY during phosphatization and indicate that studies requiring primary REY distributions or isotopic ratios should be restricted to nonphosphatized (layers of) Fe-Mn crusts. Apparent bulk coefficients, KMD, describing trace metal partitioning between nonphosphatized hydrogenetic Fe-Mn crusts and seawater, are similar for Pr to Eu and decrease for Eu to Yb. Exceptionally high values of KCeD, which are similar to those of Ti, result from oxidative scavenging of Ce and support previous suggestions that Ce(IV) is a hydroxide-dominated element in seawater. Yttrium and Gd show lower KD values than their respective neighbours in the REY series. Results of modelling the exchange equilibrium between REY dissolved in seawater and REY sorbed on hydrous Fe-Mn oxides corroborate previous studies that suggested the surface complexation of REY can be approximated by their first hydroxide binding constant. Negative "anomalies" occur for stabilities of bulk surface complexes of Gd, La, and particularly Y. The differences in inorganic surface complex stability between Y and Ho and between Gd and its REE neighbours are similar to those shown by the stabilities of complexes with aminocarboxylic acids and are significantly larger than those shown by stabilities of complexes with carboxylic acids. Hence, sorption of Y and REEs onto hydrous Fe-Mn oxides may contribute significantly to the positive YSN and GdSN anomalies in seawater.

Bau, M.; Koschinsky, A.; Dulski, P.; Hein, J.R.

1996-01-01

213

Rare earth element variations resulting from inversion of pigeonite and subsolidus reequilibration in lunar ferroan anorthosites  

USGS Publications Warehouse

We present results of a secondary ion mass spectrometry study of the rare earth elements (REEs) in the minerals of two samples of lunar ferroan anorthosite, and the results are applicable to studies of REEs in all igneous rocks, no matter what their planet of origin. Our pyroxene analyses are used to determine solid-solid REE distribution coefficients (D = CREE in low-Ca pyroxene/CREE in augite) in orthopyroxene-augite pairs derived by inversion of pigeonite. Our data and predictions from crystal-chemical considerations indicate that as primary pigeonite inverts to orthopyroxene plus augite and subsolidus reequilibration proceeds, the solid-solid Ds for orthopyroxene-augite pairs progressively decrease for all REEs; the decrease is greatest for the LREEs. The REE pattern of solid-solid Ds for inversion-derived pyroxene pairs is close to a straight line for Sm-Lu and turns upward for REEs lighter than Sm; the shape of this pattern is predicted by the shapes of the REE patterns for the individual minerals. Equilibrium liquids calculated for one sample from the compositions of primary phases, using measured or experimentally determined solid-liquid Ds, have chondrite-normalized REE patterns that are very slightly enriched in LREEs. The plagioclase equilibrium liquid is overall less rich in REEs than pyroxene equilibrium liquids, and the discrepancy probably arises because the calculated plagioclase equilibrium liquid represents a liquid earlier in the fractionation sequence than the pyroxene equilibrium liquids. "Equilibrium" liquids calculated from the compositions of inversion-derived pyroxenes or orthopyroxene derived by reaction of olivine are LREE depleted (in some cases substantially) in comparison with equilibrium liquids calculated from the compositions of primary phases. These discrepancies arise because the inversion-derived and reaction-derived pyroxenes did not crystallize directly from liquid, and the use of solid-liquid Ds is inappropriate. The LREE depletion of the calculated liquids is a relic of formation of these phases from primary LREE-depleted minerals. Thus, if one attempts to calculate the compositions of equilibrium liquids from pyroxene compositions, it is important to establish that the pyroxenes are primary. In addition, our data suggest that experimental studies have underestimated solid-liquid Ds for REEs in pigeonite and that REE contents of liquids calculated using these Ds are overestimates. Our results have implications for Sm-Nd age studies. Our work shows that if pigeonite inversion and/or subsolidus reequilibration between augite and orthopyroxene occured significantly after crystallization, and if pyroxene separates isolated for Sm-Nd studies do not have the bulk composition of the primary pyroxenes, then the Sm-Nd isochron age and ??Nd will be in error. Copyright ?? 2002 Elsevier Science Ltd.

James, O.B.; Floss, C.; McGee, J.J.

2002-01-01

214

While China's dominance in rare earths dips, concerns remain about these and other elements  

NASA Astrophysics Data System (ADS)

China's dominance in the production of rare earth elements (REEs) peaked with that nation producing 97% of them in 2010; this number already has dipped to 90% in 2012 as mines in other nations are coming online, according to REE expert Karl Gschneidner Jr., a professor at Iowa State University's Ames Laboratory. Chinese production could drop to 60% by 2014, with production increasing at mines in the United States and other countries, he said. However, this reduction in China's share of REE production does not signal an end to the production crisis in REEs and other critical minerals, Gschneidner and others noted during a 1 May panel discussion on critical materials shortages at the AGU Science Policy Conference in Washington, D. C. REEs are a group of 17 chemically similar metallic elements used in a variety of electronic, optical, magnetic, and catalytic applications, and despite their name, they are relatively plentiful in the Earth's crust. China's control of known REE reserves has dropped from 75% in 1975 to 30.9% in 2012, with other regions also having large reserves, including the Commonwealth of Independent States (some former Soviet Republic states), the United States, and Australia, according to Gschneidner. Critical minerals are mineral commodities that are particularly important for a nation's economy or national defense that could potentially face supply disruptions.

Showstack, Randy

2012-05-01

215

The History and Use of Our Earth's Chemical Elements: A Reference Guide (by Robert E. Krebs)  

NASA Astrophysics Data System (ADS)

Greenwood Press: Westport, CT, 1998. 282 pp + 25 pp glossary + 37 pp index. 15.9 x 24.1 cm. ISBN 0-313-30123-9. $39.95. This book is an excellent resource for chemical educators at the high school and college levels. The format of the text is consistent and the writing style is clear and concise, making it ideally suited for student use also. The first three chapters serve to introduce the reader to a brief history of chemistry, early models of the atom, and the development of the periodic table. Names of the contributing scientists are mentioned whenever necessary, but the overall purpose of these introductory chapters is simply to lay a foundation for the subsequent seven chapters. A complete glossary of important scientific terms mentioned in the text should allow beginning students to use this book without feeling overwhelmed. Each entry for the 112 elements contains the following information: elemental symbol, atomic number, period, common valence, atomic weight, natural state, common isotopes, properties, characteristics, abundance, natural sources, history, common uses and compounds, and safety hazards. This information is well organized, with clear headings and separate sections making the book extremely user-friendly. Readers can easily obtain the information they desire without having to skim the full entry for a chosen element. One very nice feature of this book is that the elements entries are arranged by their locations in the periodic table. For example, chapter 4 contains the alkali metals and alkaline earth metals. This organizational scheme allows one to quickly see the patterns and trends within groups of elements. This format is significantly better than arranging the elements in alphabetical order, which places the entry for sodium far removed from the entries for lithium and potassium. I would highly recommend this book to high school teachers and college chemistry professors. It is well written and is an excellent source of information for both students and educators.

Bracken, Reviewed By Jeffrey D.

1999-04-01

216

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

217

8 Sequential P Fractionation of Relict Anthropogenic Dark Earths of Amazonia  

E-print Network

-called terra preta do ´indio soils were intentionally created for agricultural purposes or whether they formed fertility of terra preta soils from the viewpoint of current soil use as well as the ori- gins of P fractionation modified by Tiessen and Moir (1993) for terra preta soils of Amazonia. Different ratios of soil

Lehmann, Johannes

218

Enrichment of rare earth elements as environmental tracers of contamination by acid mine drainage in salt marshes: a new perspective.  

PubMed

Rare earth elements (REE) were analyzed in surface sediments from the Guadiana Estuary (SW Iberian Pyrite Belt). NASC (North American Shale Composite) normalized REE patterns show clearly convex curvatures in middle-REE (MREE) with respect to light- and heavy-REE, indicating acid-mixing processes between fluvial waters affected by acid mine drainage (AMD) and seawater. However, REE distributions in the mouth (closer to the coastal area) show slightly LREE-enriched and flat patterns, indicating saline-mixing processes typical of the coastal zone. NASC-normalized ratios (La/Gd and La/Yb) do not discriminate between both mixing processes in the estuary. Instead, a new parameter (E(MREE)) has been applied to measure the curvature in the MREE segment. The values of E(MREE)>0 are indicative of acid signatures and their spatial distribution reveal the existence of two decantation zones from flocculation processes related to drought periods and flood events. Studying REE fractionation through the E(MREE) may serve as a good proxy for AMD-pollution in estuarine environments in relation to the traditional methods. PMID:22748838

Delgado, Joaquín; Pérez-López, Rafael; Galván, Laura; Nieto, José Miguel; Boski, Tomasz

2012-09-01

219

Decrease of concentration and colloidal fraction of organic carbon and trace elements in response to the anomalously hot summer 2010 in a humic boreal lake.  

PubMed

The colloidal distribution and size fractionation of organic carbon (OC), major elements and trace elements (TE) were studied in a seasonally stratified, organic-rich boreal lake, Lake Svyatoe, located in the European subarctic zone (NW Russia, Arkhangelsk region). This study took place over the course of 4 years in both winter and summer periods using an in situ dialysis technique (1 kDa, 10 kDa and 50 kDa) and traditional frontal filtration and ultrafiltration (5, 0.22 and 0.025 ?m). We observed a systematic difference in dissolved elements and colloidal fractions between summer and winter periods with the highest proportion of organic and organo-ferric colloids (1 kDa-0.22 ?m) observed during winter periods. The anomalously hot summer of 2010 in European Russia produced surface water temperatures of approximately 30°C, which were 10° above the usual summer temperatures and brought about crucial changes in element speciation and size fractionation. In August 2010, the concentration of dissolved organic carbon (DOC) decreased by more than 30% compared to normal period, while the relative proportion of organic colloids decreased from 70-80% to only 20-30% over the full depth of the water column. Similarly, the proportion of colloidal Fe decreased from 90-98% in most summers and winters to approximately 60-70% in August 2010. During this hot summer, measurable and significant (>30% compared to other periods) decreases in the colloidal fractions of Ca, Mg, Sr, Ba, Al, Ti, Ni, As, V, Co, Y, all rare earth elements (REEs), Zr, Hf, Th and U were also observed. In addition, dissolved (<0.22 ?m) TE concentrations decreased by a factor of 2 to 6 compared to previously investigated periods. The three processes most likely responsible for such a crucial change in element biogeochemistry with elevated water temperature are 1) massive phytoplankton bloom, 2) enhanced mineralization (respiration) of allochthonous dissolved organic matter by heterotrophic aerobic bacterioplankton and 3) photo-degradation of DOM and photo-chemical liberation of organic-bound TE. While the first process may have caused significant decreases in the total dissolved concentration of micronutrients (a factor of 2 to 5 for Cr, Mn, Fe, Ni, Cu, Zn and Cd and a factor of >100 for Co), the second and third factors could have brought about the decrease of allochthonous DOC concentration as well as the concentration and proportion of organic and organo-mineral colloidal forms of non-essential low-soluble trace elements present in the form of organic colloids (Al, Y, Ti, Zr, Hf, Th, Pb, all REEs). It can be hypothesized that climate warming in high latitudes capable of significantly raising surface water temperatures will produce a decrease in the colloidal fraction of most trace elements and, as a result, an increase in the most labile low molecular weight LMW(<1 kDa) fraction. PMID:23792250

Shirokova, L S; Pokrovsky, O S; Moreva, O Yu; Chupakov, A V; Zabelina, S A; Klimov, S I; Shorina, N V; Vorobieva, T Ya

2013-10-01

220

Distribution characteristics of rare earth elements in children's scalp hair from a rare earths mining area in southern China.  

PubMed

In order to demonstrate the validity of using scalp hair rare earth elements (REEs) content as a biomarker of human REEs exposure, data were collected on REEs exposure levels from children aged 11-15 years old and living in an ion-adsorptive type light REEs (LREEs) mining and surrounding areas in southern China. Sixty scalp hair samples were analyzed by ICP-MS for 16 REEs (La Lu, Y and Sc). Sixteen REEs contents in the samples from the mining area (e.g., range: La: 0.14-6.93 microg/g; Nd: 0.09-5.27 microg/g; Gd: 12.2-645.6ng/g; Lu: 0.2-13.3 ng/g; Y: 0.03-1.27 microg/g; Sc: 0.05-0.30 microg/g) were significantly higher than those from the reference area (range: La: 0.04-0.40 microg/g; Nd: 0.04-0.32 microg/g; Gd: 8.3-64.6 ng/g; Lu: 0.4-3.3ng/g; Y: 0.03-0.29 microg/g; Sc: 0.11-0.36 microg/g) and even much higher than those published in the literature. The distribution pattern of REEs in scalp hair from the mining area was very similar to that of REEs in the mine and the atmosphere shrouding that area. In conclusion, the scalp hair REEs contents may indicate not only quantitatively but also qualitatively (distribution pattern) the absorption of REEs from environmental exposure into human body. The children living in this mining area should be regarded as a high-risk group with REEs (especially LREEs) exposure, and their health status should be examined from a REEs health risk assessment perspective. PMID:15478941

Tong, Shi-Lu; Zhu, Wang-Zhao; Gao, Zhao-Hua; Meng, Yu-Xiu; Peng, Rui-Ling; Lu, Guo-Cheng

2004-01-01

221

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

222

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

223

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. This research builds on collaborations between astronomers and statisticians forged during a three week workshop on "Modern Statistical and Computational Methods for Analysis of Kepler Data" at SAMSI in June 2013.

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

2014-01-01

224

The Fractionation of Highly Siderophile Elements (HSE) in Impact Melts and the Determination of the Meteoritic Components  

NASA Astrophysics Data System (ADS)

Lunar highland rocks contain an excess of siderophile elements, which has been attributed to meteoritic influx after the formation of the lunar crust [1-4]. Siderophile element enrichment has subsequently become a standard method for the identification of terrestrial impact craters. Janssens et al. [5], Grieve [6] and Palme et al. [7] have shown the dominant role of impact melt as the main carrier of meteoritic material at large terrestrial impact craters. This has been demonstrated at Clearwater East [8], Lappajarvi [9-11], Saaksjarvi [12], Brent [6] and Rochechouart [5]. The amount of projectile material incorporated in impact melt sheets is generally low (<1%). The highest recorded is 8% at East Clearwater, where the siderophiles are carried in a sulphide phase. In other cases, searches for siderophile anomalies at some impact structure have been largely unsuccessful. Melt bearing mixed breccias (suevitic melt) and fall-back sediments have been found to be free of meteoritic components in Brent, Lappajarvi and Ries samples [6,9,12-14]. However, from approximately 130 craters which are currently known on Earth only four clearly identified chondrites have been found as projectiles of large craters [15,16]. In this study we analyzed twenty-two impact melt samples (10 g) from Saaksjarvi (Finland), Mien and Dellen (Sweden) impact craters for Os, Re, Ir, Ru, Rh, Pd and Au by a slightly modified version of the fire assay neutron activation method using nickel sulphide as the collector [13,14]. All samples were obtained from the collection of the University of Munster. Only fresh, nearly fragment-free, fine grained samples without any sign of alteration were selected for chemical studies. All samples have been described previously [17]. The INAA procedure involved two irradiations: a short irradiation for Rh and a long irradiation for the other elements. Impact melts from Saaksjarvi are highly enriched in PGEs. The flat siderophile pattern suggests that the meteoritic component (PGE/CI = 3x10^-3 to 9x10^-3 relative to CI) in the Saaksjarvi impact melt is relatively unfractionated. Stony-iron meteorites (pallasites) as proposed earlier [7] can therefore be excluded as possible contaminants because Pd and Ir are highly fractionated in pallasites [18]. Impact melts from Mien and Dellen are moderately enriched in PGE. The concentrations are similar (PGE/CI = 3x10^-4 to 1x10^-3 relative to CI). The flat siderophile pattern of the Mien and Dellen impact samples are compatible with carbonaceous chondrite type of material, but a clear geochemical association of any of the known meteorite types is not possible because of the low signal-to-background ratio for Rh, Ru, Pd, and Au. Samples from all impact craters have low Os/PGE ratios (Os/Ir(sub)melt =0.24) compared to chondritic ratios (Os/Ir(sub)CI=1.06). It seems that the oxygen fugacity at the time of impact melting, vaporization and crystallization of the melt body may play the dominant role in the fractionation of Os and PGEs. If Os have been partially lost by volatilization of OsO4 under oxidizing conditions, then Ir is the only element to confirm meteoritic enrichments down to a level of 2x10^-4 CI chondrite. None of the other elements determined are sufficiently sensitive indicators to confirm small meteoritic enrichments, equivalent to <10^-3 CI chondrite, because of low CI/Earth crust-ratios. Acknowledgements. This work was supported by DFG. References: [1] Wasson J. T. et al. (1975) Moon, 13, 121-141. [2] Gros J. et al. (1976) Proc. LSC 7th, 2403-2425. [3] Hertogen J. et al. (1977) Proc. LSC 8th, 17-45. [4] Palme H. (1980) Proc. LPSC 11th, 481-506. [5] Janssens M.-J. et al. (1977) JGR, 82, 750-758. [6] Grieve R. A. F. (1978) Proc. LPSC 9th, 2579-2608. [7] Palme H. et al. (1980) LPSC XI, 848-850. [8] Palme H. et al. (1978) GCA, 42, 313-323. [9] Reimold W. U. and Stoffler D. (1980) Meteoritics, 14, 526-528. [10] Reimold W. U. (1980) Ph. D. thesis, Univ. of Munster, 172 pp. [11] Gobel E. et al. (1980) Z. Naturforsch., 35a, 197-203. [12] Morgan J. W. et al. (1979) GCA, 4

Schmidt, G.; Palme, H.; Kratz, K. L.

1995-09-01

225

Isotopic distributions, element ratios, and element mass fractions from enrichment-meter-type gamma-ray measurements of MOX  

Microsoft Academic Search

The gamma-ray spectra from infinitely'' thick mixed oxide samples have been measured. The plutonium isotopics, the U\\/Pu ratio, the high-Z mass fractions (assuming only plutonium, uranium, and americium), and the low-Z mass fraction (assuming the matrix is only oxygen) can be determined by carefully analyzing the data. The results agree well with the chemical determination of these parameters. 8 refs.,

D. A. Close; J. L. Parker; D. L. Haycock; T. Dragnev

1991-01-01

226

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

227

Rare-earth element geochemistry and the origin of andesites and basalts of the Taupo Volcanic Zone, New Zealand  

USGS Publications Warehouse

Two types of basalt (a high-Al basalt associated with the rhyolitic centres north of Taupo and a "low-Al" basalt erupted from Red Crater, Tongariro Volcanic Centre) and five types of andesite (labradorite andesite, labradorite-pyroxene andesite, hornblende andesite, pyroxene low-Si andesite and olivine andesite/low-Si andesite) occur in the Taupo Volcanic Zone (TVZ), North Island, New Zealand. Rare-earth abundances for both basalts and andesites are particularly enriched in light rare-earth elements. High-Al basalts are more enriched than the "low-Al" basalt and have values comparable to the andesites. Labradorite and labradorite-pyroxene andesites all have negative Eu anomalies and hornblende andesites all have negative Ce anomalies. The former is probably due to changing plagioclase composition during fractionation and the latter to late-stage hydration of the magma. Least-squares mixing models indicate that neither high-Al nor "low-Al" basalts are likely sources for labradorite/labradorite-pyroxene andesites. High-Al basalts are considered to result from fractionation of olivine and clinopyroxene from a garnet-free peridotite at the top of the mantle wedge. Labradorite/labradorite-pyroxene andesites are mainly associated with an older NW-trending arc. The source is likely to be garnet-free but it is not certain whether the andesites result from partial melting of the top of the subducting plate or a hydrated lower portion of the mantle wedge. Pyroxene low-Si andesites probably result from cumulation of pyroxene and calcic plagioclase within labradorite-pyroxene andesites, and hornblende andesites by late-stage hydration of labradorite-pyroxene andesite magma. Olivine andesites, low-Si andesites and "low-Al" basalts are related to the NNE-trending Taupo-Hikurangi arc structure. Although the initial source material is different for these lavas they have probably undergone a similar history to the labradorite/labradorite-pyroxene andesites. All lavas show evidence of crustal contamination. ?? 1983.

Cole, J.W.; Cashman, K.V.; Rankin, P.C.

1983-01-01

228

'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

229

[Speciation and distribution characters of rare earth elements in the Baotou Section of the Yellow River].  

PubMed

As a whole of water column, suspended matter and surface sediment in the mainstream and the branch taking up industry wastewater, speciation and distribution characters of rare earth elements (REEs) were investigated systemically in the Baotou section of the Yellow River. This study shows that rare earth elements in the mainstream of the Baotou section of the Yellow River mainly exist in suspended particles, and the dissolved contents are in extremely minute quantities. REEs mainly exist in dissolved particles in the branch taking up industry wastewater, and suspended sigma REE and dissolved sigma REE are obviously higher than those in the mainstream. The change of sigma REE of dissolved particles in water phase along the Baotou section of the Yellow River is very similar to that of sigma REE of suspended particles, and consistent along the main river, it is that sigma REE increase appreciably from the control profile to the keystone discharged section, come to a head in the D site and reduce in the E site. This distribution pattern indicates pile industry wastewater of Baotou to rare earth elements in the mainstream of the Yellow River, particularly LREE. The REE distribution in the mainstream of the Baotou section of the Yellow River is the same, with LREE enrichment and Eu depletion. But LREE origin of D site is different from the other sites by excursion of LREE distribution curve and other geochemical parameters, they are origin of industry wastewater piled, otherwise the other four sites are origin of loess altiplano. And HREE are origin of loess altiplano in all the sites. The speciation characteristics of REE in the sediments and suspended matter are quite similar with the amount in as follows: residual > bound to carbonates, bound to Fe-Mn oxides > bound to organic matter > exchangeable. REEs exchangeable in surface sediment and suspended matter in the branch taking up industry wastewater are higher than those in the mainstream, it confirms that REEs in the mainstream mainly exist in suspended particles, and mainly exist in dissolved particles in the branch. PMID:15202236

He, Jiang; Mi, Na; Kuang, Yun-chen; Fan, Qing-yun; Wang, Xia; Guan, Wei; Li, Gui-hai; Li, Chao-sheng; Wang, Xi-wei

2004-03-01

230

Post-depositional redistribution processes and their effects on middle rare earth element precipitation and the cerium anomaly in sediments in the South Korea Plateau, East Sea  

NASA Astrophysics Data System (ADS)

We sampled two box-core sediments from the slope of the eastern South Korea Plateau (SKP) in the East Sea (Sea of Japan) at water depths of 1400 and 1700 m. Two chemical fractions of extractable (hydroxylamine/acetic acid) and residual rare earth elements (REEs) together with Al, Ca, Fe, Mg, Mn, P, S, As, Mo, and U were analyzed to assess the post-depositional redistribution of REEs. Extractable Fe and Mn are noticeably abundant in the oxic topmost sediment layer (<3 cm). However, some trace elements (e.g., S, As, Mo, U) are more abundant at depth, where redox conditions are different. Analysis of upper continental crust (UCC)-normalized (La/Gd)UCC, (La/Yb)UCC, and (Ce/Ce*)UCC revealed that the extractable REE is characterized by middle REE (MREE) enrichment and a positive cerium (Ce) anomaly, different from the case of the residual fraction which shows slight enrichment in light REEs (LREEs) with no Ce anomaly. The extractable MREEs seem to have been incorporated into high-Mg calcite during reductive dissolution of Fe oxyhydroxides. In the top sediment layer, the positive Ce anomaly is attributed to Ce oxide, which can be mobilized in deeper oxygen-poor environments and redistributed in the sediment column. In addition, differential concentrations of Ce and other LREEs in pore water appear to result in variable (Ce/Ce*)UCC ratios in the extractable fraction at depth.

Kang, Jeongwon; Jeong, Kap-Sik; Cho, Jin Hyung; Lee, Jun Ho; Jang, Seok; Kim, Seong Ryul

2014-03-01

231

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

232

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

233

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

234

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

235

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

236

Examination of rare earth element concentration patterns in freshwater fish tissues.  

PubMed

Rare earth elements (REEs or lanthanides) were measured in ten freshwater fish species from a reservoir in Washington State (United States). The REE distribution patterns were examined within fillet and whole body tissues for three size classes. Total concentrations (?REE) ranged from 0.014 to 3.0mgkg(-1) (dry weight) and averaged 0.243mgkg(-1) (dry weight). Tissue concentration patterns indicated that REEs accumulated to a greater extent in organs, viscera, and bone compared to muscle (fillet) tissues. Benthic feeding species (exposed to sediments) exhibited greater concentrations of REEs than pelagic omnivorous or piscivorous fish species. Decreasing REE concentrations were found with increasing age, total length or weight for largescale and longnose suckers, smallmouth bass, and walleye. Concentration patterns in this system were consistent with natural conditions without anthropogenic sources of REEs. These data provide additional reference information with regard to the fate and transport of REEs in freshwater fish tissues in a large aquatic system. PMID:25000508

Mayfield, David B; Fairbrother, Anne

2015-02-01

237

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

238

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

239

Spinel-silicate Mg and Fe stable isotope fractionation: a model system to explore isotope partitioning in the deep Earth  

NASA Astrophysics Data System (ADS)

We find that insights into the partitioning of heavy and light non-traditional stable isotopes between minerals are gained by treating the force constants representing bonds in spinels and some silicates as purely electrostatic in origin. As a result, magnesium and iron isotope fractionations between spinel oxide minerals and silicates offer an unparalleled opportunity to explore the causes of stable isotope fractionation. The purely ionic model has severe limitations, but it is nonetheless useful for explaining isotope fractionation between spinels and silicates, and may be similarly valuable as a tool for predicting fractionation between some other phases in planetary interiors. The electrostatic calculation is based on Pauling's bond strength si where si = zi/?i. Here zi is the absolute value of the valence of ion i and ?i is the coordination number for the ion. Bond strengths can substitute for valence in an equation for the electrostatic force constant kf for the bond between cations i and anions j such that kf =si sj e2 (n-1)/(4? ?o r3ij) where ?o is the electric constant, e is the charge of an electron, and n is the Born-Mayer ion repulsion term (empirically derived). This simple formulation of bonding, together with known inter-atomic bond distances rij, reproduces the 26Mg/24Mg fractionation factors between MgAl2O4 spinel (Spl) and Mg-rich olivine (Ol) in two mantle xenoliths [1], 57Fe/54Fe fractionation between Spl and Ol in the xenoliths [2], and the 57Fe/54Fe fractionation between magnetite (Mgt) and fayalite (Fa) in the laboratory [3] within a factor of 2 or better. For example, the experimentally-determined ?57FeMgt-Fa at 1000 K is 0.30 ‰. The calculated value is 0.56 ‰, with half of the effect attributable to the differences in Fe coordination and the other half due to valence. We measured a ?57FeSpl-Ol of 0.17 ‰ in a xenolith. The electrostatic prediction is also 0.17 ‰ at the rock equilibration T of 1080 K. This is in contrast to predictions based on Mössbauer data that give the opposite sign for the fractionation [4]. For Mg in the xenoliths, the measured ?26MgSpl-Ol value is 0.8 ‰ and the electrostatic prediction is 0.6 ‰. We use this simple tool to explore Mg isotope fractionation in Earth's deep mantle. Garnet (e.g., Mg3Al2Si3O12, Grt) and ringwoodite (Mg2SiO4, Rng) are the two dominant phases of the transition zone. Consideration of the different coordination environments of Mg (MgVIII vs. MgVI, respectively) suggests a ?26MgGrt-Rng of -0.1 ‰ at ~ 18 GPa and 1800 K. This fractionation may be large enough to be evident in the products of partial melting in this region of the mantle. [1] Young et al. (2009, submitted); [2] Macris et al. (2008, AGU abstr.); [3] Shahar, Young, and Manning (2007, EPSL); [4] Polyakov et al. (2007, GCA).

Young, E. D.; Schauble, E. A.; Macris, C.

2009-12-01

240

Geology and market-dependent significance of rare earth element resources  

NASA Astrophysics Data System (ADS)

China started to produce rare earth elements (REEs) in the 1980s, and since the mid-1990s, it has become the dominant producer. Rare earth element export quotas first introduced by the Chinese government in the early 2000s were severely reduced in 2010 and 2011. This led to strong government-created disparity between prices within China and the rest of the world. Industrialized countries identified several REEs as strategic metals. Because of rapid price increases of REE outside of China, we have witnessed a world-scale REE exploration rush. The REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, monazite ± apatite veins, ion adsorption clays, placers, and some deep ocean sediments. REE could also be derived as a by-product of phosphate fertilizer production, U processing, mining of Ti-Zr-bearing placers, and exploitation of Olympic Dam subtype iron oxide copper gold (IOCG) deposits. Currently, REEs are produced mostly from carbonatite-related deposits, but ion adsorption clay deposits are an important source of heavy REE (HREE). Small quantities of REE are derived from placer deposits and one peralkaline intrusion-related deposit. The ideal REE development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia. REE grade, HREE/light REE (LREE) ratio of the mineralization, tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen potential development projects. As REEs are considered strategic metals from economic, national security, and environmental points of view, technical and economic parameters alone are unlikely to be used in REE project development decision-making. Recycling of REE is in its infancy and unless legislated, in the short term, it is not expected to contribute significantly to the supply of REE.

Simandl, G. J.

2014-09-01

241

Geology and market-dependent significance of rare earth element resources  

NASA Astrophysics Data System (ADS)

China started to produce rare earth elements (REEs) in the 1980s, and since the mid-1990s, it has become the dominant producer. Rare earth element export quotas first introduced by the Chinese government in the early 2000s were severely reduced in 2010 and 2011. This led to strong government-created disparity between prices within China and the rest of the world. Industrialized countries identified several REEs as strategic metals. Because of rapid price increases of REE outside of China, we have witnessed a world-scale REE exploration rush. The REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, monazite ± apatite veins, ion adsorption clays, placers, and some deep ocean sediments. REE could also be derived as a by-product of phosphate fertilizer production, U processing, mining of Ti-Zr-bearing placers, and exploitation of Olympic Dam subtype iron oxide copper gold (IOCG) deposits. Currently, REEs are produced mostly from carbonatite-related deposits, but ion adsorption clay deposits are an important source of heavy REE (HREE). Small quantities of REE are derived from placer deposits and one peralkaline intrusion-related deposit. The ideal REE development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia. REE grade, HREE/light REE (LREE) ratio of the mineralization, tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen potential development projects. As REEs are considered strategic metals from economic, national security, and environmental points of view, technical and economic parameters alone are unlikely to be used in REE project development decision-making. Recycling of REE is in its infancy and unless legislated, in the short term, it is not expected to contribute significantly to the supply of REE.

Simandl, G. J.

2014-12-01

242

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

243

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

244

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

245

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

246

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

247

The geochemistry of the volatile trace elements As, Cd, Ga, In and Sn in the Earth’s mantle: New evidence from in situ analyses of mantle xenoliths  

NASA Astrophysics Data System (ADS)

The abundances of 30 trace elements, including the volatile chalcophile/siderophile elements As, Cd, Ga, In and Sn were determined by laser ablation ICP-MS in minerals of 19 anhydrous and 5 hydrous spinel peridotite xenoliths from three continents. The majority of samples were fertile lherzolites with more than 5% clinopyroxene; several samples have major element compositions close to estimates of the primitive mantle. All samples have been previously analysed for bulk-rock major, minor and lithophile trace elements. They cover a wide range of equilibration temperatures from about 850 to 1250 °C and a pressure range from 0.8 to 3.0 GPa. A comparison of results from bulk-rock analyses with concentrations obtained from combining silicate and oxide mineral data with modal mineralogy, gave excellent agreement, with the exception of As. Arsenic is the only element analysed that has high concentrations in sulphides. For all other elements sulphides can be neglected as host phases in these mantle rocks. The major host phase for Cd, In and Sn is clinopyroxene and if present, amphibole. Cadmium and In appear to behave moderately incompatibly during mantle melting similar to Yb. The data yield new and more reliable mantle abundances for Cd (35 ± 7 ppb), In (18 ± 3 ppb) and Sn (91 ± 28 ppb). The In value is similar to the Mg and CI-normalized Zn abundance of the mantle, although In is cosmochemically more volatile than Zn. The high In content suggests a high content of volatile elements in general in proto-Earth material. The lower relative abundances of volatile chalcophile elements such as Cd, S, Se and Te might be explained by sulphide segregation during core formation. The very low relative abundances of volatile and highly incompatible lithophile elements such as Br, Cl and I, and also C, N and rare gases, imply loss during Earth accretion, arguably by collisional erosion from differentiated planetesimals and protoplanets.

Witt-Eickschen, G.; Palme, H.; O'Neill, H. St. C.; Allen, C. M.

2009-03-01

248

Effects of exogenous rare earth elements on phosphorus adsorption and desorption in different types of soils.  

PubMed

Phosphorus (P) is an important biogeochemical element and the environmental fate of P receives increasing attention. Through batch equilibration experiments, the adsorption and desorption of P in the absence and presence of exogeneous rare earth elements (REEs) were investigated in five types of agricultural soil samples collected from China. The results showed that the addition of different doses of REEs had influences on P adsorption processes in the soils, and there were differences in different soil types and different P concentrations of the P solutions. The amount of P adsorption tended to decline when the five types of soils were amended with low concentrations of REEs. The characteristics of P adsorption were more complicated when high concentrations of REEs were added to the different soils. Affected by the high concentrations of REEs, when the P concentration of the P solution added to soils was less than 20 mg L(-1), the rate of P adsorption tended to increase in all the five types of soils. However, when the P concentration of the P solution added to soil was greater than 30 mg L(-1), the rate of P adsorption tended to decrease. The Langmuir equation fitted P adsorption in all the five types of soils well. Compared with the control, when soil samples were amended with REEs, the P desorption rates of the five types of soils increased. PMID:24342358

Wang, Lingqing; Liang, Tao

2014-05-01

249

Distribution and size fractionation of elemental sulfur in aqueous environments: The Chesapeake Bay and Mid-Atlantic Ridge  

NASA Astrophysics Data System (ADS)

Elemental sulfur is an important intermediate of sulfide oxidation and may be produced via abiotic and biotic pathways. In this study the concentration and size fractionation of elemental sulfur were measured in two different sulfidic marine environments: the Chesapeake Bay and buoyant hydrothermal vent plumes along the Mid-Atlantic Ridge. Nanoparticulate sulfur (<0.2 ?m) was found to comprise up to 90% of the total elemental sulfur in anoxic deep waters of the Chesapeake Bay. These data were compared with previous studies of elemental sulfur, and represent one of the few reports of nanoparticulate elemental sulfur in the environment. Additionally, a strain of phototrophic sulfide oxidizing bacteria isolated from the Chesapeake Bay was shown to produce elemental sulfur as a product of sulfide oxidation. Elemental sulfur concentrations are also presented from buoyant hydrothermal vent plumes located along the Mid-Atlantic Ridge. In the Mid-Atlantic Ridge plume, S0 concentrations up to 33 ?M were measured in the first meter of rising plumes at three different vent sites, and nanoparticulate S0 was up to 44% of total elemental sulfur present.

Findlay, Alyssa J.; Gartman, Amy; MacDonald, Daniel J.; Hanson, Thomas E.; Shaw, Timothy J.; Luther, George W.

2014-10-01

250

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

251

Deposition and element fractionation processes during atmospheric pressure laser sampling for analysis by ICP-MS  

Microsoft Academic Search

We have used an ArF excimer laser coupled to a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) for the measurement of a range of elements during excavation of a deepening ablation pit in a synthetic glass (NIST 612). Analyte behaviour shows progressive volatile element enrichment at shallow hole depths, with a change to refractory element enrichment as the ablation pit

S. M. Eggins; L. P. J. Kinsley; J. M. G. Shelley

1998-01-01

252

Three-level hybrid vs. flat MPI on the Earth Simulator: Parallel iterative solvers for finite-element method  

Microsoft Academic Search

An efficient parallel iterative method for finite element method has been developed for symmetric multiprocessor (SMP) cluster architectures with vector processors such as the Earth Simulator. The method is based on a three-level hybrid parallel programming model, including message passing for inter-SMP node communication, loop directives by OpenMP for intra-SMP node parallelization and vectorization for each processing element (PE). Simple

Kengo Nakajima

2005-01-01

253

New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars  

Microsoft Academic Search

We have derived new abundances of the rare earth elements Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five elements are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper,

Christopher Sneden; James E. Lawler; John J. Cowan; Inese I. Ivans; Elizabeth A. Den Hartog; Inese I

2009-01-01

254

Earth's Atmosphere  

NSDL National Science Digital Library

This problem set is about the methods scientists use to compare the abundance of the different elements in Earth's atmosphere. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

255

Combined thermodynamic and rare earth element modelling of garnet growth during subduction: Examples from ultrahigh-pressure eclogite of the Western Gneiss  

E-print Network

Combined thermodynamic and rare earth element modelling of garnet growth during subduction Keywords ultrahigh-pressure metamorphism garnet trace elements Western Gneiss Region thermodynamic modeling garnets from the Western Gneiss Region (Norway). All investigated garnets show multiple growth zones

Zack, Thomas

256

Treatment of a waste salt delivered from an electrorefining process by an oxidative precipitation of the rare earth elements  

NASA Astrophysics Data System (ADS)

For the reuse of a waste salt from an electrorefining process of a spent oxide fuel, a separation of rare earth elements by an oxidative precipitation in a LiCl-KCl molten salt was tested without using precipitate agents. From the results obtained from the thermochemical calculations by HSC Chemistry software, the most stable rare earth compounds in the oxygen-used rare earth chlorides system were oxychlorides (EuOCl, NdOCl, PrOCl) and oxides (CeO 2, PrO 2), which coincide well with results of the Gibbs free energy of the reaction. In this study, similar to the thermochemical results, regardless of the sparging time and molten salt temperature, oxychlorides and oxides were formed as a precipitant by a reaction with oxygen. The structure of the rare earth precipitates was divided into two shapes: small cubic (oxide) and large plate-like (tetragonal) structures. The conversion efficiencies of the rare earth elements to their molten salt-insoluble precipitates were increased with the sparging time and temperature, and Ce showed the best reactivity. In the conditions of 650 °C of the molten salt temperature and 420 min of the sparging time, the final conversion efficiencies were over 99.9% for all the investigated rare earth chlorides.

Cho, Yung-Zun; Yang, Hee-Chul; Park, Gil-Ho; Lee, Han-Soo; Kim, In-Tae

2009-02-01

257

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

1954-01-01

258

Strontium isotopes and rare earth elements as tracers of groundwater–lake water interactions, Lake Naivasha, Kenya  

Microsoft Academic Search

Strontium isotope compositions and rare earth element (REE) concentrations are presented for groundwater and surface water samples collected from the Lake Naivasha watershed in the East African Rift, Kenya. The chief objective of the study is to test the suitability of REEs, in conjunction with Sr isotopes, as tools for investigating groundwater–lake water interactions. In general, the REE concentrations and

S. Bwire Ojiambo; W. Berry Lyons; Kathy A. Welch; Robert J. Poreda; Karen H. Johannesson

2003-01-01

259

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

260

PII S0016-7037(02)00888-8 EXAFS study of rare-earth element coordination in calcite  

E-print Network

PII S0016-7037(02)00888-8 EXAFS study of rare-earth element coordination in calcite E. J. ELZINGA,1 , Sm3 , Dy3 , Yb3 ) coprecipitated with calcite in minor concentrations from room-temperature aqueous are longer than the Ca-O distance in calcite and longer than what is consistent with ionic radii sums

Peale, Robert E.

261

Effect of some light rare earth elements on seed germination, seedling growth and antioxidant metabolism in Triticum durum  

Microsoft Academic Search

Rare earth elements (REEs) enriched fertilizers have been commonly used in China since the 1980s, thus inducing a growing concern about their environmental impact in agriculture. In this work, the effect of some light REEs nitrate mixture and La3+ nitrate on seed germination, seedling growth and antioxidant metabolism in Triticum durum was investigated with the aim of clarifying the potential

Luigi d’Aquino; Maria Concetta de Pinto; Luca Nardi; Massimo Morgana; Franca Tommasi

2009-01-01

262

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

263

Hydrothermal transport and deposition of the rare earth elements by fluorine-bearing aqueous liquids  

NASA Astrophysics Data System (ADS)

New technologies, particularly those designed to address environmental concerns, have created a great demand for the rare earth elements (REE), and focused considerable attention on the processes by which they are concentrated to economically exploitable levels in the Earth's crust. There is widespread agreement that hydrothermal fluids played an important role in the formation of the world's largest economic REE deposit, i.e. Bayan Obo, China. Until recently, many researchers have assumed that hydrothermal transport of the REE in fluorine-bearing ore-forming systems occurs mainly due to the formation of REE-fluoride complexes. Consequently, hydrothermal models for REE concentration have commonly involved depositional mechanisms based on saturation of the fluid with REE minerals due to destabilization of REE-fluoride complexes. Here, we demonstrate that these complexes are insignificant in REE transport, and that the above models are therefore flawed. The strong association of H+ and F- as HF° and low solubility of REE-F solids greatly limit transport of the REE as fluoride complexes. However, this limitation does not apply to REE-chloride complexes. Because of this, the high concentration of Cl- in the ore fluids, and the relatively high stability of REE-chloride complexes, the latter can transport appreciable concentrations of REE at low pH. The limitation also does not apply to sulphate complexes and in some fluids, the concentration of sulphate may be sufficient to transport significant concentrations of REE as sulphate complexes, particularly at weakly acidic pH. This article proposes new models for hydrothermal REE deposition based on the transport of the REE as chloride and sulphate complexes.

Migdisov, Art A.; Williams-Jones, A. E.

2014-12-01

264

Rare earth and major element geochemistry of Eocene fine-grained sediments in oil shale- and coal-bearing layers of the Meihe Basin, Northeast China  

NASA Astrophysics Data System (ADS)

The Meihe Basin is a Paleogene pull-apart basin. Long-flame coal, lignite and oil shale are coexisting energy resources deposited in this basin. Ninety-seven samples, including oil shales, coals, brown to gray silt and mudstone, have been collected from the oil shale- and coal-bearing layers to discover the rare earth element geochemistry. The total REE contents of oil shales and coals are 137-256 ?g/g and 64-152 ?g/g respectively. The chondrite-normalized patterns of oil shales and coals show LREE enrichments, HREE deficits, negative Eu anomalies and negligible Ce anomalies. The chemical index of alteration (CIA) as well as some trace elements is often used to reflect the paleoenvironment at the time of deposition. The results show that fine-grained sediments in both layers were deposited in dysoxic to oxic conditions and in a warm and humid climate, and coals were deposited in a warmer and more humid climate than oil shales. Oil shales and coals are both in the early stage of diagenesis and of terrigenous origin. Besides, diagrams of some major, trace and rare earth elements show that the fine-grained sediments of both layers in the Meihe Basin are mainly from the felsic volcanic rocks and granite, and that their source rocks are mostly deposited in the continental inland arc setting. The analysis of major elements shows that Si, Al, K and Ti, in both layers, are found mainly in a mixed clay mineral assemblage and that Si is also found in quartz. Sodium occurs primarily in clay minerals, whereas Ca is found mainly in the organic matter. In the coal-bearing layer, iron is mainly controlled by organic matter rather than detrital minerals. In contrast, in the oil shale-bearing layer, neither detrital minerals nor organic matter exert a control on the iron content. Analyzing the relationship between rare earth elements and major elements shows that REEs in the oil shales and the coals are both of terrigenous origin and are mainly controlled by detrital minerals rather than by organic matter. In both layers, REEs have no relationship with fine-grained phosphates, and during the weathering process, the REEs were not very mobile and were resistant to fractionation.

Bai, Yueyue; Liu, Zhaojun; Sun, Pingchang; Liu, Rong; Hu, Xiaofeng; Zhao, Hanqing; Xu, Yinbo

2015-01-01

265

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

266

Apatite/liquid partition coefficients for the rare earth elements and strontium  

NASA Astrophysics Data System (ADS)

Sixteen sets of apatite/liquid partition coefficients ( D ap/liq) for the rare earth elements (REE; La, Sm, Dy, Lu) and six values for Sr were experimentally determined in natural systems ranging from basanite to granite. The apatite + melt (glass) assemblages were obtained from starting glasses artificially enriched in REE, Sr and fluorapatite components; these were run under dry and hydrous conditions of 7.5-20 kbar and 950-1120°C in a solid-media, piston-cylinder apparatus. An SEM-equipped electron microprobe was used for subsequent measurement of REE and Sr concentrations in coexisting apatites and quenched glasses. The resulting partition coefficient patterns resemble previously determined apatite phenocryst/groundmass concentration ratios in the following respects: (1) the rare earth patterns are uniformly concave downward (i.e., the middle REE are more compatible in apatite than the light and heavy REE); (2) D REEap/liq is much higher for silicic melts than for basic ones; and (3) strontium (and therefore Eu 2+) is less concentrated by apatite than are the trivalent REE. The effects of both temperature and melt composition on D REEap/liq are systematic and pronounced. At 950°C, for example, a change in melt SiO 2 content from 50 to 68 wt.% causes the average REE partition coefficient to increase from ˜7 to ˜30. A 130°C increase in temperature, on the other hand, results in a two-fold decrease in D REEap/liq. Partitioning of Sr is insenstitive to changes in melt composition and temperature, and neither the Sr nor the REE partition coefficients appear to be affected by variations in pressure or H 2O content of the melt. The experimentally determined partition coefficients can be used not only in trace element modelling, but also to distinguish apatite phenocrysts from xenocrysts in rocks. Reported apatite megacryst/host basalt REE concentration ratios [12], for example, are considerably higher than the equilibrium partition coefficients, which suggest that in this particular case the apatite is actually xenocrystic. A reversal experiment incorporated in our study yielded diffusion profiles of REE in apatite, from which we extracted a REE?Ca interdiffusion coefficient of 2-4×10 -14 cm 2/s at 1120°C. Extrapolated downward to crustal temperatures, this low value suggests that complete REE equilibrium between felsic partial melts and residual apatite is rarely established.

Watson, E. Bruce; Green, Trevor H.

1981-12-01

267

Distribution of rare earth elements in marine sediments from the Strait of Sicily (western Mediterranean Sea): evidence of phosphogypsum waste contamination.  

PubMed

Concentrations of rare earth elements (REE), Y, Th and Sc were recently determined in marine sediments collected using a box corer along two onshore-offshore transects located in the Strait of Sicily (Mediterranean Sea). The REE+Y were enriched in offshore fine-grained sediments where clay minerals are abundant, whereas the REE+Y contents were lower in onshore coarse-grained sediments with high carbonate fractions. Considering this distribution trend, the onshore sediments in front of the southwestern Sicilian coast represent an anomaly with high REE+Y concentrations (mean value 163.4 ?g g(-1)) associated to high Th concentrations (mean value 7.9 ?g g(-1)). Plot of shale-normalized REE+Y data of these coastal sediments showed Middle REE enrichments relative to Light REE and Heavy REE, manifested by a convexity around Sm-Gd-Eu elements. These anomalies in the fractionation patterns of the coastal sediments were attributed to phosphogypsum-contaminated effluents from an industrial plant, located in the southern Sicilian coast. PMID:21130477

Tranchida, G; Oliveri, E; Angelone, M; Bellanca, A; Censi, P; D'Elia, M; Neri, R; Placenti, F; Sprovieri, M; Mazzola, S

2011-01-01

268

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.

269

Extreme trace elements fractionation in Cenozoic nephelinites and phonolites from the Moroccan Anti-Atlas (Eastern Saghro)  

NASA Astrophysics Data System (ADS)

Nephelinites and phonolites from the Moroccan Anti-Atlas form a cogenetic series of volcanic rocks linked by a fractional crystallization process and showing continuous evolutionary trends for trace-elements. According to partial melting calculations, minor element data in olivine and review of published experimental studies, the most primitive nephelinites are low degree (~ 2%) partial melts from a carbonated LREE-rich spinel lherzolite. Sr-Nd-Pb isotopic compositions indicate the participation of both DM and HIMU end-members in the mantle source of nephelinites; the HIMU component is here interpreted as a relic of the shallow metasomatized Pan-African mantle. The phonolites show similar isotopic composition except for slightly more radiogenic Sr isotopic values. Fractional crystallization calculations were performed using trace-element mineral/bulk rock coefficients determined with new LA-ICP-MS data on minerals together with published equilibrium partition coefficients. The decrease of LREE, Sr and Ba with increasing differentiation is explained by fractionation of large amounts of apatite. Th, Nb and Zr display a behavior of very incompatible elements, reaching extreme concentration in most differentiated phonolites. Ta, Hf and MREE by contrast are characterized by a moderately incompatible to compatible behavior during differentiation. Fractionation of small amount of titanite, in which Ta, Hf and MREE are highly compatible compared to Nb, Zr and LREE (DNb/DTa: 2, DZr/DHf: 1.5 for titanite/phonolite ratios), explains the observed increase in Nb/Ta and Zr/Hf ratios with increasing silica content, from 18 and 40 in nephelinites to 70 and 80 in phonolites, respectively. Clinopyroxene also contributed to the fractionation of Hf from Zr in the very first steps of crystallization. The low values of Nb/Ta and Zr/Hf ratios observed in the two most differentiated Si-rich phonolites are probably a consequence of late stage segregation of volatile-rich agpaitic assemblages in the underlying magma chamber. Two phonolites with extreme Sr contents plot outside fractionation trends, as a result of the remelting of previously crystallized nephelinitic rocks in depth.

Berger, Julien; Ennih, Nasser; Liégeois, Jean-Paul

2014-12-01

270

Rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments  

NASA Astrophysics Data System (ADS)

Analyses have been made of REE contents of a well-characterized suite of deep-sea (> 4000 m.) principally todorokite-bearing ferromanganese nodules and associated sediments from the Pacific Ocean. REE in nodules and their sediments are closely related: nodules with the largest positive Ce anomalies are found on sediments with the smallest negative Ce anomalies; in contrast, nodules with the highest contents of other rare earths (3 + REE) are found on sediments with the lowest 3 + REE contents and vice versa. 143Nd /144Nd ratios in the nodules (˜0.51244) point to an original seawater source but an identical ratio for sediments in combination with the REE patterns suggests that diagenetic reactions may transfer elements into the nodules. Analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to REE contents of nodules and sediments is negligible. Inter-element relationships and leaching tests suggest that REE contents are controlled by a P-rich phase with a REE pattern similar to that for biogenous apatite and an Fe-rich phase with a pattern the mirror image of that for sea water. It is proposed that 3 + REE concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate. Processes which favour the enrichment of transition metals in equatorial Pacific nodules favour the depletion of 3 + REE in nodules and enrichment of 3 + REE in associated sediments. In contrast, Ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions.

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

1981-04-01

271

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

272

71Atomic Numbers and Multiplying Fractions Number, Z, of an element  

E-print Network

that is 2/5 of astatine (At)? Problem 5 - Which element has an atomic number that is 5 1/8 that of sulfur (S (germanium). Problem 4 - Which element has an atomic number that is 2/5 of Astatine (At)? Answer; Astatine=85

273

Elemental and Isotopic Fractionation in ^He-rich Solar Energetic Particle Events  

Microsoft Academic Search

Using data from the Solar Isotope Spectrometer (SIS) on the Advanced Composition Explorer (ACE) mission, heavy ion composition measurements have been made in 26 He-rich solar energetic particle (SEP) events that occurred between 1998 and 2004. Relative abundances of 13 elements from C through Ni have been investigated, as have the isotopic compositions of the elements Ne and Mg. We

M. E. Wiedenbeck; R. A. Leske; C. M. S. Cohen; A. C. Cummings; R. A. Mewaldt; E. C. Stone; T. T. von Rosenvinge

274

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

SciTech Connect

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 {Sigma}REE concentrations of {le} 6 ppm. REE patterns range from (1) strongly enriched in light REE with positive Eu anomalies, to (2) relatively flat with positive Eu anomalies and slightly negative Ce anomalies, to (3) slightly enriched in light REE with moderately negative Ce anomalies. Pattern 1 is similar to that of 300-350 C solutions discharging at vents on the East Pacific Rise and the Mid-Atlantic Ridge, whereas pattern 3 resembles REE distributions in normal oceanic bottom waters. The sulfide-sulfate patterns are interpreted to result from variable mixtures of hydrothermal and normal seawater. Barite in gossans capping the mounds has an REE pattern almost identical to patterns of high-temperature vent solutions. Hydrothermal barite has lower REE contents and a different REE pattern relative to hydrogenous barite formed slowly on the sea floor.

Barrett, T.J. (McGill Univ., Montreal, Quebec (Canada)); Jarvis, I. (School of Geological Sciences, Surrey (England)); Jarvis, K.E. (Univ. of Surrey, Guildford, Surrey (England))

1990-07-01

275

Effect of Rare Earth Elements on Isothermal Transformation Kinetics in Si-Mn-Mo Bainite Steels  

NASA Astrophysics Data System (ADS)

Isothermal heat treatments to Si-Mn-Mo steel specimens were performed, and time-temperature-transformation curves (C-curves) were plotted by DIL805A/D differential dilatometer. The effect of rare earth (RE) elements on bainite transformation kinetics was systematically studied by adopting the empirical electron theory of solids and molecules, Johnson-Mehl-Avrami equation calculation, dilatometry, and metallography. Experimental results show that the addition of RE in Si-Mn-Mo bainite steels leads to the C-curves moving to bottom right and prolongs incubation period of bainite transformation. Moreover, RE addition increases the values of phase structure factors ( n A, F {C/D}) and activation energy of bainite transformation, inhibits the formation of granular bainite, and refines microstructures of bainitic ferrite and substructures. During the bainite transformation process, bainite transformation is delayed due to the drag effect, which is induced by the segregation of RE at the ferrite interphase and the retardation of Fe-C-RE (segregation units) on carbon diffusion.

Liang, Yilong; Yi, Yanliang; Long, Shaolei; Tan, Qibing

2014-12-01

276

Effect of Rare Earth Elements on Isothermal Transformation Kinetics in Si-Mn-Mo Bainite Steels  

NASA Astrophysics Data System (ADS)

Isothermal heat treatments to Si-Mn-Mo steel specimens were performed, and time-temperature-transformation curves (C-curves) were plotted by DIL805A/D differential dilatometer. The effect of rare earth (RE) elements on bainite transformation kinetics was systematically studied by adopting the empirical electron theory of solids and molecules, Johnson-Mehl-Avrami equation calculation, dilatometry, and metallography. Experimental results show that the addition of RE in Si-Mn-Mo bainite steels leads to the C-curves moving to bottom right and prolongs incubation period of bainite transformation. Moreover, RE addition increases the values of phase structure factors (n A, F {C/D}) and activation energy of bainite transformation, inhibits the formation of granular bainite, and refines microstructures of bainitic ferrite and substructures. During the bainite transformation process, bainite transformation is delayed due to the drag effect, which is induced by the segregation of RE at the ferrite interphase and the retardation of Fe-C-RE (segregation units) on carbon diffusion.

Liang, Yilong; Yi, Yanliang; Long, Shaolei; Tan, Qibing

2014-09-01

277

Rare earth elements in an ice core from Mt. Everest: Seasonal variations and potential sources  

NASA Astrophysics Data System (ADS)

Rare earth element (REE) concentrations in ice samples from the upper 8.4 m of a Mt. Everest ice core retrieved from the col of the East Rongbuk Glacier (28.03°N, 86.96°E, 6518 m a.s.l.) on the northeast ridge of Mt. Everest in September 2002 are presented. REEs display large seasonal variations, with high concentrations in the non-monsoon season and low concentrations in the summer monsoon season. This seasonality is useful for ice core dating. When normalized to a shale standard, the Mt. Everest REEs exhibit a consistent shale-like pattern with a slight enrichment of middle REEs during both seasons. However, individual monsoon REE patterns display differences, possibly resulting from diversified sources. Non-monsoon REE patterns are stable and are associated with the westerlies. Investigation of potential sources for the Everest REEs suggests an absence of anthropogenic contributions and minimal input from local provenances. REEs in Mt. Everest samples are most likely representative of a stable well-mixed REE background of the upper troposphere consisting of a mixture of aerosols transported by the atmospheric circulation from the west windward arid regions such as the Thar Desert, West Asia, the Sahara Desert and other uncertain provenances.

Zhang, Qianggong; Kang, Shichang; Kaspari, Susan; Li, Chaoliu; Qin, Dahe; Mayewski, Paul A.; Hou, Shugui

2009-10-01

278

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

279

Effect of Ca and Rare Earth Elements on Impression Creep Properties of AZ91 Magnesium Alloy  

NASA Astrophysics Data System (ADS)

Creep properties of AZ91 magnesium alloy and AZRC91 (AZ91 + 1 wt pct RE + 1.2 wt pct Ca) alloy were investigated using the impression creep method. It was shown that the creep properties of AZ91 alloy are significantly improved by adding Ca and rare earth (RE) elements. The improvement in creep resistance is mainly attributed to the reduction in the amount and continuity of eutectic ?(Mg17Al12) phase as well as the formation of new Al11RE3 and Al2Ca intermetallic compounds at interdendritic regions. It was found that the stress exponent of minimum creep rate, n, varies between 5.69 and 6 for AZ91 alloy and varies between 5.81 and 6.46 for AZRC91 alloy. Activation energies of 120.9 ± 8.9 kJ/mol and 100.6 ± 7.1 kJ/mol were obtained for AZ91 and AZRC91 alloys, respectively. It was shown that the lattice and pipe-diffusion-controlled dislocation climb are the dominant creep mechanisms for AZ91 and AZRC91 alloys, respectively. The constitutive equations, correlating the minimum creep rate with temperature and stress, were also developed for both alloys.

Nami, B.; Razavi, H.; Mirdamadi, S.; Shabestari, S. G.; Miresmaeili, S. M.

2010-08-01

280

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

281

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

282

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

283

Time of Formation of Earth and Mars Constrained by Siderophile Element Geochemistry and the Hafnium-182-Tungsten-182 Isotope System  

NASA Astrophysics Data System (ADS)

182Hf-182W chronometry is considered the most powerful tool to determine the formation timescale of the terrestrial planets. However, previous work employed oversimplified accretion and core formation models. The accretion and core formation models presented here for the 182W isotopic evolution in the mantles of the accreting Earth and Mars, can incorporate the core formation conditions constrained by siderophile element geochemistry and can be successfully applied to constrain the formation timescale of Earth and Mars. Elemental abundance analyses of the Allende meteorite and two martian meteorites lead to new estimates of core-mantle concentration ratios of Si, V, Cr and Mn for Earth and two distinct mantle Hf/W ratios for Mars respectively, and provide better constraints on the models. It is concluded that formation of the proto-Earth (˜87% of its present mass) has to complete rapidly in 10.7 +/- 2.5 Myr after the onset of the Solar System for a late (? 52 Myr) Moon-forming giant impact. The mean time of Mars' accretion is determined to be 3.6 +/- 0.1 Myr, meaning that Mars accretes to 95% of its present mass in 10.8 +/- 0.3 Myr after the formation of the Solar System. Therefore, Mars is not a planetary embryo, and Mars and proto-Earth may be formed on a similar timescale if a late Moon-forming giant impact is assumed. In contrast, if the Moon formed early at ˜30 Myr then it takes about 3 times longer to form the proto-Earth compared to Mars. A stochastic mantle stirring and sampling model was developed to investigate the evolution of W isotope heterogeneities in the mantles of Earth and Mars after accretion and core formation. Our results confirm the mantle stirring rate of ˜ 500 Myr constrained by the long-lived isotope systems in Earth and suggest that the mantle stirring rate in Mars is much slower (˜2 Ga). A new concept is developed: the core formation memory of a siderophile element. Siderophile elements are shown to have different capabilities in recording core formation history, a very important fact to consider in any core formation modeling.

Yu, Gang

284

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

285

(Published in Environmental Science and Pollution Research) Potentially toxic element fractionation in technosoils using two  

E-print Network

. Surface soils were samples from a waste landfill contaminated with Zn, Pb, and Cd located at Mortagne-du- Nord (MDN; North France) and from a settling basin contaminated with PTE such as As, Pb, and Sb located, and Pb were mainly associated with the acid soluble and reducible fractions for MDN site, while As, Sb

Boyer, Edmond

286

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

287

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

288

Microstructure and properties of 17-4PH steel plasma nitrocarburized with a carrier gas containing rare earth elements  

SciTech Connect

The effect of rare earth addition in the carrier gas on plasma nitrocarburizing of 17-4PH steel was studied. The microstructure and crystallographically of the phases in the surface layer as well as surface morphology of the nitrocarburized specimens were characterized by optical microscope, X-ray diffraction and scanning tunneling microscope, respectively. The hardness of the surface layer was measured by using a Vickers hardness test. The results show that the incorporation of rare earth elements in the carrier gas can increase the nitrocarburized layer thickness up to 55%, change the phase proportion in the nitrocarburized layer, refine the nitrides in surface layer, and increase the layer hardness above 100HV. The higher surface hardening effect after rare earth addition is caused by improvement in microstructure and change in the phase proportion of the nitrocarburized layer.

Liu, R.L., E-mail: ruiliangliu@126.com [National Key Laboratory for Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Yan, M.F., E-mail: yanmufu@hit.edu.cn [National Key Laboratory for Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wu, Y.Q. [National Key Laboratory for Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhao, C.Z. [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin150001 (China)

2010-01-15

289

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

290

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

291

Laboratory simulation of meteoritic noble gases. III - Sorption of neon, argon, krypton, and xenon on carbon - Elemental fractionation  

NASA Astrophysics Data System (ADS)

The sorption of Ne, Ar, Kr, and Xe was studied in carbon black, acridine carbon, and diamond in an attempt to understand the origin of trapped noble gases in meteorites. The results support a model in which gases are physically adsorbed on interior surfaces formed by a pore labyrinth within amorphous carbons. The data show that: (1) the adsorption/desorption times are controlled by choke points that restrict the movement of noble gas atoms within the pore labyrinth, and (2) the physical adsorption controls the temperature behavior and elemental fractionation patterns.

Wacker, J. F.

1989-06-01

292

Laboratory simulation of meteoritic noble gases. III - Sorption of neon, argon, krypton, and xenon on carbon - Elemental fractionation  

NASA Technical Reports Server (NTRS)

The sorption of Ne, Ar, Kr, and Xe was studied in carbon black, acridine carbon, and diamond in an attempt to understand the origin of trapped noble gases in meteorites. The results support a model in which gases are physically adsorbed on interior surfaces formed by a pore labyrinth within amorphous carbons. The data show that: (1) the adsorption/desorption times are controlled by choke points that restrict the movement of noble gas atoms within the pore labyrinth, and (2) the physical adsorption controls the temperature behavior and elemental fractionation patterns.

Wacker, John F.

1989-01-01

293

Riparian Dendrochemistry: Detecting Rare-Earth Elements in Trees along an Effluent- Dominated Desert River  

NASA Astrophysics Data System (ADS)

This research documents spatial and temporal patterns of effluent uptake by riparian trees through development of a new and innovative application for dendrochronology, specifically dendrochemistry. The rare-earth element (REE) gadolinium (Gd), is a known micro-pollutant that enters streams from wastewater treatment plants. Gd was first used in select medical procedures in 1988 and subsequently discharged via treatment plants into waterways. Trees uptake Gd but do not utilize it, thereby providing a specific presence/absence date stamp in tree rings and making it an ideal marker of effluent water use by trees. Results from this study along an effluent-dominated portion of the Santa Cruz River in southeastern Arizona, show elevated levels of Gd in surface flows and the presence of Gd in cottonwood (Populus fremontii) growth rings. The first indication of Gd in tree rings occurred around 1988, and concentrations increased through 2000 followed by a sharp decline from 2001-2005. These dendrochronological results suggest that a clogging layer prevented effluent from infiltrating and recharging groundwater tables during the 2001-2005 drought period, thus reducing concentrations of Gd and other REEs in the groundwater tables. Since riparian trees depend on groundwater for some or all of their water needs, a reduction of Gd in tree rings indicates reduced effluent concentrations in groundwater and therefore a limited connection between the river and the groundwater due to a clogging layer. The impact of effluent quality on the chemical composition of tree rings is a useful monitoring tool to evaluate temporal patterns of surface water quality, the extent of surface and groundwater interactions, and the influence of effluent on riparian ecosystems.

McCoy, A. L.; Sheppard, P. R.; Meixner, T.

2008-12-01

294

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

295

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

296

The rare earth element potential of kaolin deposits in the Bohemian Massif (Czech Republic, Austria)  

NASA Astrophysics Data System (ADS)

Four kaolin deposits in the Bohemian Massif were studied in order to assess the potential for the recovery of rare earth elements (REE) as by-products from the residue after extraction and refining of the raw kaolin. The behaviour of REE + Y during kaolinitization was found to be largely a function of pre-alteration mineralogy. In the examples studied, i.e. granite-derived deposits of Kriechbaum (Austria) and Boži?any, and arkose-derived deposits of Kazn?jov and Podbo?any (all Czech Republic), the REE + Y are predominantly hosted by monazite which has remained unaffected by kaolinitization. The overall REE + Y content of the variably kaolinitized rocks is strongly dependent on their genesis. While ion adsorption plays only a minor role in the concentration of REE + Y in the studied kaolinitized rocks, the processing and refining of the raw kaolin leads to residues that are enriched in REE + Y by a factor of up to 40. The use of a magnetic separator and a hydrocyclone in the processing of the raw material can yield REE + Y contents of as much as 0.77 wt%. Although this value compares well with the REE + Y concentration in some potentially economic REE + Y projects elsewhere, the overall tonnage of the (REE + Y)-enriched residue is by far not sufficient to consider economic extraction of REE + Y as by-product. Our results are most probably applicable also to other kaolin deposits derived from the weathering of Hercynian basement granites elsewhere (e.g. in Saxonia and Bavaria, Germany). Overall, the potential for REE + Y production as by-product from kaolin mining has to be regarded as minimal.

Höhn, S.; Frimmel, H. E.; Pašava, J.

2014-12-01

297

Rare earth element concentrations in geological and synthetic samples using synchrotron X-ray fluorescence analysis  

USGS Publications Warehouse

The concentrations of rare earth elements (REEs) in specific mineral grains from the Bayan Obo ore deposit and synthetic high-silica glass samples have been measured by synchrotron X-ray fluorescence (SXRF) analysis using excitation of the REE K lines between 33 and 63 keV. Because SXRF, a nondestructive analytical technique, has much lower minimum detection limits (MDLs) for REEs, it is an important device that extends the in situ analytical capability of electron probe microanalysis (EPMA). The distribution of trace amounts of REEs in common rock-forming minerals, as well as in REE minerals and minerals having minor quantities of REEs, can be analyzed with SXRF. Synchrotron radiation from a bending magnet and a wiggler source at the National Synchrotron Light Source, Brookhaven National Laboratory, was used to excite the REEs. MDLs of 6 ppm (La) to 26 ppm (Lu) for 3600 s in 60-??m-thick standard samples were obtained with a 25-??m diameter wiggler beam. The MDLs for the light REEs were a factor of 10-20 lower than the MDLs obtained with a bending magnet beam. The SXRF REE concentrations in mineral grains greater than 25 ??m compared favorably with measurements using EPMA. Because EPMA offered REE MDLs as low as several hundred ppm, the comparison was limited to the abundant light REEs (La, Ce, Pr, Nd). For trace values of medium and heavy REEs, the SXRF concentrations were in good agreement with measurements using instrumental neutron activation analysis (INAA), a bulk analysis technique. ?? 1993.

Chen, J.R.; Chao, E.C.T.; Back, J.M.; Minkin, J.A.; Rivers, M.L.; Sutton, S.R.; Cygan, G.L.; Grossman, J.N.; Reed, M.J.

1993-01-01

298

Rare-earth elements and Nd and Pb isotopes as source indicators for Labrador Sea clay-size sediments during Heinrich event 2  

USGS Publications Warehouse

Elemental abundances and Nd and Pb isotope ratios were determined on samples from the carbonate-free, clay-size fractions of sediments from intervals above, within, and below Heinrich event 2 (H-2) in core HU87-9 from the Northwest Labrador Sea slope. In HU87-9, rare-earth element (REE) distributions and elemental concentrations within the H-2 event are distinct from those outside this event, ??Nd(0) and 206Pb/204Pb data also indicate different values for sediments deposited within and outside the H-2 event. Comparisons of REE patterns from the H-2 interval with those from bedrock units in Baffin Island, northern Quebec, and Labrador indicate that the Lake Harbour Group (LHG), which crops out on the north side of the Hudson Strait, is the most probable bedrock source of the clay-size fraction found within the H-2 interval in HU87-9. The Tasiuyak Gneiss (TG) and Lac Lomier Complex (LLC) have REE patterns (including a negative Eu anomaly) similar to those found in H-2 sediments; however, the La/Yb ratios of these units are smaller than those associated with H-2 sediments. The Nd and Pb isotope data support and complement REE-based interpretations of provenance; i.e., the Nd-Pb signatures of sediments deposited at the HU87-9 site during the H-2 event are similar to Nd-Pb signatures obtained on diamicts from the western end of Hudson Strait. Published by Elsevier Science Ltd.

Benson, L.; Barber, D.; Andrews, J.T.; Taylor, H.; Lamothe, P.

2003-01-01

299

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

300

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

301

Experimental Investigation of Evaporation Behavior of Polonium and Rare-Earth Elements in Lead-Bismuth Eutectic Pool  

SciTech Connect

Equilibrium evaporation behavior was experimentally investigated for polonium ({sup 210}Po) in liquid lead-bismuth eutectic (LBE) and for rare-earth elements gadolinium (Gd) and europium (Eu) in LBE to understand and clarify the transfer behavior of toxic impurities from LBE coolant to a gas phase. The experiments utilized the 'transpiration method' in which saturated vapor in an isothermal evaporation pot was transported by inert carrier gas and collected outside of the pot. While the previous paper ICONE12-49111 has already reported the evaporation behavior of LBE and of tellurium in LBE, this paper summarizes the outlines and the results of experiments for important impurity materials {sup 210}Po and rare-earth elements which are accumulated in liquid LBE as activation products and spallation products. In the experiments for rare-earth elements, non-radioactive isotope was used. The LBE pool is about 330-670 g in weight and has a surface area of 4 cm x 14 cm. {sup 210}Po experiments were carried out with a smaller test apparatus and radioactive {sup 210}Po produced through neutron irradiation of LBE in the Japan Materials Testing Reactor (JMTR). We obtained fundamental and instructive evaporation data such as vapor concentration, partial vapor pressure of {sup 210}Po in the gas phase, and gas-liquid equilibrium partition coefficients of the impurities in LBE under the temperature condition between 450 and 750 deg. C. The {sup 210}Po test revealed that Po had characteristics to be retained in LBE but was still more volatile than LBE solvent. A part of Eu tests implied high volatility of rare-earth elements comparable to that of Po. This tendency is possibly related to the local enrichment of the solute near the pool surface and needs to be investigated more. These results are useful and indispensable for the evaluation of radioactive materials transfer to the gas phase in LBE-cooled nuclear systems. (authors)

Shuji Ohno; Shinya Miyahara; Yuji Kurata [Japan Atomic Energy Agency (Japan); Ryoei Katsura [Nippon Nuclear Fuel Development Co., Ltd. (Japan); Shigeru Yoshida [KAKEN Co., Ltd. (Japan)

2006-07-01

302

Geochemistry of rare-earth elements in spinel lherzolites of mantle nodules - A model of the primitive mantle  

Microsoft Academic Search

Data obtained by Stosch (1986) on the geochemistry of REEs in spinel lherzolites of mineral nodules from alkaline basaltoids of the Shavaryn-Tsaram feature in Central Mongolia were used to construct a model for primitive-mantle geochemistry compatible with the obtained distribution of petrogenic and rare-earth elements. It is pointed out that a petrochemically primitive mantle taking no account of an alkaline

V. I. Kovalenko; I. D. Riabchikov; H.-G. Stosch

1989-01-01

303

Species and distribution of rare earth elements in the Baotou section of the Yellow River in China  

Microsoft Academic Search

This paper analyses the contents and species distributions of rare earth elements (REEs) in the water-suspended particulate-sediment\\u000a system of the Baotou section of the Yellow River, China, with known anthropogenic REE input from industrial discharges. The\\u000a major forms of REEs were suspended and dissolved in the mainstream and the tributaries of the Baotou section, respectively.\\u000a The concentrations of the dissolved

Jiang He; Chang-Wei Lü; Hong-Xi Xue; Ying Liang; Saruli Bai; Ying Sun; Li-Li Shen; Na Mi; Qing-Yun Fan

2010-01-01

304

Preparation and Photocatalysis Properties of Bacterial Cellulose\\/TiO2 Composite Membrane Doped with Rare Earth Elements  

Microsoft Academic Search

Bacterial cellulose (BC) was chosen as a support for nanometer titanium dioxide (TiO2) particles due to its superfine network structure. The composite membrane of TiO2\\/BC doped with rare earth elements was prepared by a sol-gel method using tetraisopropyl titanate as starting material. Photocatalysis properties of this composite membrane were estimated by using methyl orange as a degradation agent. X-ray fluorescence

Xiuju Zhang; Wenbin Chen; Zhidan Lin; Jia Yao; Shaozao Tan

2011-01-01

305

Three-dimensional finite-element modelling of Earth's viscoelastic deformation: effects of lateral variations in lithospheric thickness  

Microsoft Academic Search

We have developed a 3-D spherical finite-element model to study the dynamic response to surface loads of a self-gravitating and incompressible Earth with 3-D viscoelastic structure. We have forced our model with the ICE-3G deglaciation history of Tushingham & Peltier to study the effects of laterally varying lithospheric thickness on observations of post-glacial rebound (PGR). The laterally varying lithospheric thicknesses

Shijie Zhong; Archie Paulson; John Wahr

2003-01-01

306

A model for continental crust genesis by arc accretion: rare earth element evidence from the Irish Caledonides  

Microsoft Academic Search

The formation of continental crust is a complex problem with a paradox at its center: continental material is believed to form by arc magmatism, a model that does not reconcile the bulk mafic and light rare earth element (LREE)-depleted composition of intra-oceanic arcs with the andesitic, LREE-enriched composition of continents. We present evidence supporting an arc origin for continental crust

Amy E. Draut; Peter D. Clift; Robyn E. Hannigan; Graham Layne; Nobumichi Shimizu

2002-01-01

307

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

308

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

309

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

310

Distribution of rare earth elements and neodymium isotopes in settling particulate material of the tropical Atlantic Ocean (EUMELI site)  

Microsoft Academic Search

We analysed rare earth element (REE) concentrations and Nd isotopic ratios of large sinking particles to investigate chemical scavenging processes. The sinking particles were collected with time-series sediment traps at 2500 m at two sites in the tropical northeastern Atlantic: a mesotrophic site (M-site: 18°N, 21°W) and an oligotrophic site (O-site: 21°N, 31°W). Shalenormalized REE patterns of the trapped material

K. Tachikawa; C. Handel; B. Dupre

1997-01-01

311

Rare-earth elements and uranium in high-temperature solutions from East Pacific Rise hydrothermal vent field (13 °N)  

Microsoft Academic Search

The mobility of rare-earth elements (REE) and U during hydrothermal alteration of the basalts at spreading centres has long been a matter of concern because of its bearing on the evolution and recycling of the oceanic crust1-6. Previous approaches to this problem have been indirect, through studies on altered dredged basalts or ophiolites. We report here sampling of hydrothermal vent

A. Michard; F. Albarède; G. Michard; J. F. Minster; J. L. Charlou

1983-01-01

312

Platinum group elements and gold in ferromanganese crusts from Afanasiy-Nikitin seamount, equatorial Indian Ocean: Sources and fractionation  

USGS Publications Warehouse

The major element relationships in ferromanganese (Fe-Mn) crusts from Afanasiy-Nikitin seamount (ANS), eastern equatorial Indian Ocean, appear to be atypical. High positive correlations (r = 0.99) between Mn/Co and Fe/Co ratios, and lack of correlation of those ratios with Co, Ce, and Ce/Co, indicate that the ANS Fe-Mn crusts are distinct from Pacific seamount Fe-Mn crusts, and reflect region-specific chemical characteristics. The platinum group elements (PGE: Ir, Ru, Rh, Pt, and Pd) and Au in ANS Fe-Mn crusts are derived from seawater and are mainly of terrestrial origin, with a minor cosmogenic component. The Ru/Rh (0.5-2) and Pt/Ru ratios (7-28) are closely comparable to ratios in continental basalts, whereas Pd/Ir ratios exhibit values ( 0.75) correlations between water depth and Mn/Co, Fe/Co, Ce/Co, Co, and the PGEs. Fractionation of the PGE-Au from seawater during colloidal precipitation of the major-oxide phases is indicated by well-defined linear positive correlations (r > 0.8) of Co and Ce with Ir, Ru, Rh, and Pt; Au/Co with Mn/Co; and by weak or no correlations of Pd with water depth, Co-normalized major-element ratios, and with the other PGE (r < 0.5). The strong enrichment of Pt (up to 1 ppm) relative to the other PGE and its positive correlations with Ce and Co demonstrate a common link for the high concentrations of all three elements, which likely involves an oxidation reaction on the Mn-oxide and Fe-oxyhydroxide surfaces. The documented fractionation of PGE-Au and their positive association with redox sensitive Co and Ce may have applications in reconstructing past-ocean redox conditions and water masses.

Banakar, V.K.; Hein, J.R.; Rajani, R.P.; Chodankar, A.R.

2007-01-01

313

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

314

Mineral chemistry of Rare Earth Element (REE) mineralization, Browns Ranges, Western Australia  

NASA Astrophysics Data System (ADS)

‘Green energy futures’ are driving unprecedented demand for Rare Earth Elements (REE), underpinning significant exploration activity worldwide. Understanding how economic REE concentrations form is critical for development of exploration models. REE mineralisation in the Browns Ranges, Gordon Downs Region, Western Australia, comprises xenotime-dominant mineralisation hosted within Archaean to Palaeoproterozoic metasedimentary units (Browns Range Metamorphics). Mineralogical, petrographic and mineral-chemical investigation, including trace element analysis by Laser-Ablation Inductively-Coupled Plasma Mass Spectroscopy, gives insights into the mineralogical distribution and partitioning of REE, and also provides evidence for the genetic evolution of the Browns Range REE mineralisation via a succession of hydrothermal processes. Two main REE-bearing minerals are identified: xenotime [(Y,REE)PO4], which is HREE selective; and subordinate florencite [(REEAl3(PO4)2(OH)6] which is LREE selective. Two morphological generations of xenotime are recognised; compositions are however consistent. Xenotime contains Dy (up to 6.5 wt.%), Er (up to 4.35 wt.%), Gd (up to 7.56 wt.%), Yb (up to 4.65 wt.%) and Y (up to 43.3 wt.%). Laser Ablation ICP-MS element mapping revealed a subtle compositional zoning in some xenotime grains. LREE appear concentrated in the grain cores or closest to the initial point of growth whereas HREE, particularly Tm, Yb and Lu, are highest at the outer margins of the grains. The HREE enrichment at the outer margins is mimicked by As, Sc, V, Sr, U, Th and radiogenic Pb. Florencite is commonly zoned and contains Ce (up to 11.54 wt.%), Nd (up to 10.05 wt.%) and La (up to 5.40 wt.%) and is also notably enriched in Sr (up to 11.63 wt.%) and Ca. Zircon (which is not a significant contributor of REEs overall due to its low abundance in the rocks) is also enriched in REE (up to 13 wt.% ?REE) and is the principal host of Sc (up to 0.8 wt.%). Early, coarse euhedral xenotime has undergone fracturing, partial breakdown and replacement by florencite. Second generation xenotime occurs as abundant small blades commonly associated with acicular hematite. Mineralization is attributed to percolation of a volatile-rich, acidic fluid, possibly granite-derived, through porous arkose units. Late hematite may suggest mixing with meteoric water and subsequent oxidation. Field observations suggest that faults acted as fluid conduits and that brecciation, possibly associated with release of volatiles from the fluid, occurred along these faults. The data provide valuable constraints on chemical compositional trends in xenotime and coexisting minerals. Given the current surge in exploration for REE, this information will assist in the development of exploration models for comparable terranes.

Cook, Nigel J.; Ciobanu, Cristiana L.; O'Rielly, Daniel; Wilson, Robin; Das, Kevin; Wade, Benjamin

2013-07-01

315

Rare earth element sorption by basaltic rock: Experimental data and modeling results using the “Generalised Composite approach”  

NASA Astrophysics Data System (ADS)

Sorption of the 14 rare earth elements (REE) by basaltic rock is investigated as a function of pH, ionic strength and aqueous REE concentrations. The rock sample, originating from a terrestrial basalt flow (Rio Grande do Sul State, Brazil), is composed of plagioclase, pyroxene and cryptocrystalline phases. Small amounts of clay minerals are present, due to rock weathering. Batch sorption experiments are carried out under controlled temperature conditions of 20 °C with the <125 ?m fraction of the ground rock in solutions of 0.025 M and 0.5 M NaCl and at pH ranging from 2.7 to 8. All 14 REEs are investigated simultaneously with initial concentrations varying from 10 -7 to 10 -4 mol/L. Some experiments are repeated with only europium present to evaluate possible competitive effects between REE. Experimental results show the preferential retention of the heavy REEs at high ionic strength and circumneutral pH conditions. Moreover, results show that REE sorption increases strongly with decreasing ionic strength, indicating two types of sorption sites: exchange and specific sites. Sorption data are described by a Generalised Composite (GC) non-electrostatic model: two kinds of surface reactions are treated, i.e. cation exchange at >XNa sites, and surface complexation at >SOH sites. Total site density (>XNa + >SOH) is determined by measuring the cation exchange capacity (CEC = 52 ?mol/m 2). Specific concentrations of exchange sites and complexation sites are determined by fitting the Langmuir equation to sorption isotherms of REE and phosphate ions. Site densities of 22 ± 5 and 30 ± 5 ?mol/m 2 are obtained for [>XNa] and [>SOH], respectively. The entire set of REE experimental data is modeled using a single exchange constant (log Kex = 9.7) and a surface complexation constant that progressively increases from log K = -1.15 for La(III) to -0.4 for Lu(III). The model proves to be fairly robust in describing other aluminosilicate systems. Maintaining the same set of sorption constants and only adjusting the site densities, we obtain good agreement with the literature data on REE/kaolinite and REE/smectite sorption. The Generalised Composite non-electrostatic model appears as an easy and efficient tool for describing sorption by complex aluminosilicate mineral assemblages.

Tertre, E.; Hofmann, A.; Berger, G.

2008-02-01

316

Chemical fractionations in meteorites. V - Volatile and siderophile elements in achondrites and ocean ridge basalts.  

NASA Technical Reports Server (NTRS)

Eighteen achondrites and 4 terrestrial basalts (3 ocean ridge, 1 continental) were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Co, Cs, Cu, Ga, In, Ir, Rb, Se, Tl and Zn. Samples included 7 eucrites, 5 howardites, 2 nakhlites, 2 shergottites, an angrite, and an aubrite. Light and dark portions of the gas-rich meteorites Kapoeta and Pesyanoe were analyzed separately. Nakhlites and shergottites have volatile element abundances similar to those in ocean ridge basalts; eucrites, howardites, and angrites show greater depletions by an order of magnitude and less similar abundance patterns. In terms of a two-component model of planetary accretion, the parent planets contained the following percentages of low-temperature material: eucrites 0.8, nakhlites 38, shergottites 28. Shergottites may be genetically related to L-chondrites. The siderophile element pattern of achondrites resembles that of the moon, but with less extreme depletions.

Laul, J. C.; Keays, R. R.; Ganapathy, R.; Anders, E.; Morgan, J. W.

1972-01-01

317

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

318

Rare-earths in size fractions and sedimentary rocks of Pennsylvanian-Permian age from the mid-continent of the U.S.A  

Microsoft Academic Search

The REE (rare-earth) contents of sixty-three <2 fractions of Pennsylvanian and Permian platform sediment from the mid-continent of the U.S.A. vary considerably ( REE = 46-439 ppm;La\\/ Lu = 5.2-15.7; correlation coefficient of REE with La\\/Lu = 0.89), but the Eu\\/Sm ratios are nearly constant even in reducing environments that concentrate U (0.16-0.22). There is no correlation of REE content

Robert Cullers; Sambhudas Chaudhuri; Neil Kilbane; Richard Koch

1979-01-01

319

Improving Low-Earth Orbit Predictions Using Two-line Element Data with Bias Correction  

NASA Astrophysics Data System (ADS)

In this paper we present results from our orbit prediction study using the publicly available Two-Line Element (TLE) sets. The method presented here is similar to that introduced by Levit and Marshall; however, we also consider the non-spherical low-Earth orbit satellites Grace A and Grace B. The method uses 10 days of TLE data which is interpolated using SGP4. A state vector is generated every 10 minutes in the orbit determination (OD) period. These generated states are subsequently used as observations in an orbit determination run considering a full set of forces to determine the orbit over the 10-day time span. All information used is from the TLE data sets. Once the orbit has been determined, it is then numerically propagated to obtain a prediction of the object's position. The TLE-determined orbit is compared to highly accurate satellite laser ranging (SLR) Consolidated Prediction Format (CPF) data to assess the accuracy. We tested the technique by performing 200 independent simulations for Stella, Starlette, Grace A and Grace B and found that it resulted in better orbit predictions 98.5%, 93.4%, 97.5% and 95.5% of the time, respectively, when compared to standard SGP4 propagation. For Stella and Starlette after a 7 day prediction period the average absolute maximum along track bias was reduced by approximately 64% and 74%, respectively. For Grace A and Grace B after a 7 day prediction period the average absolute maximum along track bias was reduced by approximately 68% and 64%, respectively. The TLE-determined orbit contains bias in the along, across and radial tracks with the along track error dominating. If these can be estimated we can obtain an improved orbit prediction. We used our TLE-determined orbit as an initial state and determined an orbit 3 days after the 10 day OD period from only two passes of SLR data from a single station (Mount Stromlo, Australia). We then estimated the bias in the along track direction by fitting a quadratic function to the along track bias data. The error between the TLE-determined orbit and the SLR-determined orbit in the along (minus the quadratic bias), across and radial tracks was then estimated using sinusoidal functions. These estimations were then used to correct the TLE-determined orbit, resulting in drastic improvements in the prediction accuracy of low-Earth objects. For a prediction period of 7 days, the absolute maximum along track error for Grace A reduced from 16.6 km (SGP4) to 4.8 km with the TLE data fitting presented in this paper. With bias estimation this error was reduced to 1.7 km. This demonstrates the ability to obtain much more accurate orbit predictions using only two passes (19 normal point SLR ranging observations) from one station. In the operational sense, the presented method can be used in debris conjunction analyses to improve the accuracy and reliability of the conjunction predictions. This method is currently implemented in EOSSS' conjunction analysis software. Objects of interest can then be tracked with EOSSS' tracking facilities and much better orbit predictions can be obtained.

Bennett, J.; Sang, J.; Smith, C.; Zhang, K.

2012-09-01

320

Rare earth elements as indicators of hydrothermal processes within the East Scotia subduction zone system  

NASA Astrophysics Data System (ADS)

The East Scotia subduction zone, located in the Atlantic sector of the Southern Ocean, hosts a number of hydrothermal sites in both back-arc and island-arc settings. High temperature (>348 °C) ‘black smoker’ vents have been sampled at three locations along segments E2 and E9 of the East Scotia back-arc spreading ridge, as well as ‘white smoker’ (<212 °C) and diffuse (<28 °C) hydrothermal fluids from within the caldera of the Kemp submarine volcano. The composition of the endmember fluids (Mg = 0 mmol/kg) is markedly different, with pH ranging from <1 to 3.4, [Cl-] from ?90 to 536 mM, [H2S] from 6.7 to ?200 mM and [F-] from 35 to ?1000 ?M. All of the vent sites are basalt- to basaltic andesite-hosted, providing an ideal opportunity for investigating the geochemical controls on rare earth element (REE) behaviour. Endmember hydrothermal fluids from E2 and E9 have total REE concentrations ranging from 7.3 to 123 nmol/kg, and chondrite-normalised distribution patterns are either light REE-enriched (LaCN/YbCN = 12.8-30.0) with a positive europium anomaly (EuCN/Eu?CN = 3.45-59.5), or mid REE-enriched (LaCN/NdCN = 0.61) with a negative Eu anomaly (EuCN/Eu?CN = 0.59). By contrast, fluids from the Kemp Caldera have almost flat REE patterns (LaCN/YbCN = 2.1-2.2; EuCN/Eu?CN = 1.2-2.2). We demonstrate that the REE geochemistry of fluids from the East Scotia back-arc spreading ridge is variably influenced by ion exchange with host minerals, phase separation, competitive complexation with ligands, and anhydrite deposition, whereas fluids from the Kemp submarine volcano are also affected by the injection of magmatic volatiles which enhances the solubility of all the REEs. We also show that the REE patterns of anhydrite deposits from Kemp differ from those of the present-day fluids, potentially providing critical information about the nature of hydrothermal activity in the past, where access to hydrothermal fluids is precluded.

Cole, Catherine S.; James, Rachael H.; Connelly, Douglas P.; Hathorne, Ed C.

2014-09-01

321

Rare earth element metasomatism in hydrothermal systems: The Willsboro-Lewis wollastonite ores, New York, USA  

USGS Publications Warehouse

Wollastonite ores and garnet-pyroxene skarns in the Willsboro-Lewis district, New York, USA were formed in a complex hydrothermal system associated with the emplacement of a large anorthosite pluton. Contact-metamorphic marbles were replaced by wollastonite, garnet, and clinopyroxene during infiltration metasomatism involving large volumes of water of chiefly meteoric origin. Rare earth elements (REE) in these rocks show large departures from the protolith REE distribution, indicative of substantial REE mobility. Three types of chondrite-normalized REE distribution patterns are present. The most common, found in ores and skarns containing andradite-rich garnet, is convex-up in the light REE (LREE) with a maximum at Pr and a positive Eu anomaly. Europium anomalies and Pr/Yb ratios are correlated with X(Ad) in garnet. This pattern (type C) results from uptake of REE from hydrothermal fluids by growing crystals of calcsilicate minerals, principally andradite, with amounts of LREE controlled by the difference in ionic radius between Ca++ and REE3+ in garnet X sites. The Eu anomaly results either from prior interaction of the fluids with plagioclase-rich, Eu-positive anorthositic rocks in and near the ore zone, or by enrichment of divalent Eu on growth surfaces of garnet followed by entrapment, or both. Relative enrichment in heavy REE (type H) occurs in ores and skarn where calcsilicates, including grossularitic garnet, in contact-metamorphic marble have been concentrated by dissolution of calcite. In most cases a negative Eu anomaly is inherited from the marble protolith. Skarns containing titanite and apatite exhibit high total REE, relative light REE enrichment, and negative Eu anomalies (type L). These appear to be intrusive igneous rocks (ferrodiorites or anorthositic gabbros) that have been converted to skarn by Ca metasomatism. REE, sequestered in titanite, apatite, and garnet, preserve the approximate REE distribution pattern of the igneous protolith. Post-ore granulite facies metamorphism homogenized zoned mineral grains without causing complete intergranular reequilibration and does not appear to have significantly affected the whole-rock REE distributions. These results demonstrate that extensive REE metasomatism can occur in hydrothermal systems at shallow to intermediate depths and that REE geochemistry may be useful in discerning the origin of skarns and skarn-related ore deposits.

Whitney, P.R.; Olmsted, J.F.

1998-01-01

322

Isotopic and elemental fractionation of solar wind implanted in the Genesis concentrator target characterized and quantified by noble gases  

NASA Astrophysics Data System (ADS)

We report concentrations and isotopic compositions of He, Ne, and Ar measured with high spatial resolution along a radial traverse of a silicon carbide (SiC) quadrant of the Genesis mission concentrator target. The Ne isotopic composition maps instrumental fractionation as a function of radial position in the target: the maximum observed isotopic fractionation is approximately 33‰ per mass unit between the center and periphery. The Ne fluence is enhanced by a factor of 43 at the target center and decreases to 5.5 times at the periphery relative to the bulk solar wind fluence. Neon isotopic profiles measured along all four arms of the "gold cross" mount which held the quadrants in the concentrator target demonstrate that the concentrator target was symmetrically irradiated during operation as designed. We used implantation experiments of Ne into SiC and gold to quantify backscatter loss and isotopic fractionation and compared measurements with numerical simulations from the code "stopping and range of ions in matter." The 20Ne fluence curve as a function of radial distance on the target may be used to construct concentration factors relative to bulk solar wind for accurate corrections for solar wind fluences of other light elements to be measured in the concentrator target. The Ne isotopic composition as a function of the radial distance in the SiC quadrant provides a correction for the instrumental mass-dependent isotopic fractionation by the concentrator and can be used to correct measured solar wind oxygen and nitrogen isotopic compositions to obtain bulk solar wind isotopic compositions.

Heber, Veronika S.; Wiens, Roger C.; Jurewicz, Amy J. G.; Vogel, Nadia; Reisenfeld, Daniel B.; Baur, Heinrich; McKeegan, Kevin D.; Wieler, Rainer; Burnett, Donald S.

2011-04-01

323

Natural and anthropogenic rare earth elements in Lago de Paranoá, Brasilia, Brazil  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) belong to the group of particle reactive elements and occur at ultratrace levels in natural waters. They are exclusively trivalent, but Ce and Eu can also be tetravalent and divalent, respectively, depending on the redox-level, the pH and the temperature of the fluid. Due to these redox changes, normalized REE patterns may show Ce and/or Eu anomalies. Recently, these high-tech metals raised significant public attention, as they are of great economic importance and consumption and hence release into the environment increased sharply. The most prominent example of a REE contamination is anthropogenic Gd, which is derived from Gd-based contrast agents used in magnetic resonance imaging. Due to their high stabilities, these compounds are not readily removed by commonly applied waste water treatment technologies and, therefore, are released from treatment plants into surface and ground waters. Hence, this anthropogenic Gd can be used as a tracer for the presence of waste water-derived substances such as pharmaceuticals and personal care products in river, lake, ground and tap waters. Lago de Paranoá is an artificial reservoir lake in the city of Brasilia, Brazil, and is currently considered a potential freshwater resource. The city's two waste water treatment plants are located on its shore and their effluents are discharged into the lake. To investigate the level of contamination, we took water samples at 11 stations in the lake and compared the REE concentrations in unfiltered and filtered (<200 nm) lake water. The unfiltered water samples show light REE enrichment (LaSN/YbSN: 1.37-1.98) and high REE concentrations (Sum REE: 192 - 476 ng/L), while the unfiltered water samples are heavy REE enriched (LaSN/YbSN: 0.15-0.61) at lower concentrations (Sum REE: 50 - 85 ng/L). This is due to the fact that light REE are preferentially bound to particle surfaces, while the heavy REE are preferentially complexed with ligands in solution. In marked contrast to the filtered samples, REE patterns of the unfiltered waters show a positive anomaly of redox-sensitive Ce. This reveals oxidative scavenging of Ce onto particles in the lake water. As lithic particles, such as atmospheric dust, do not show positive Ce anomalies, the particles responsible for Ce oxidation are either inorganic Mn or Fe (oxyhydr-) oxides or organic particulates, which are known to oxidatively scavenge Ce. All samples show pronounced positive Gd anomalies, revealing the presence of waste water-derived anthropogenic Gd in the lake waters. Because the anthropogenic Gd is bound to a very stable water-soluble chemical complex, it does not react with particles. Hence, both the filtered and unfiltered samples show REE patterns with a similar-sized positive Gd anomaly. The presence of anthropogenic Gd indicates that other waste water-derived substances of potentially high (eco-) toxicity may also be present in the lake water. This needs to be further investigated and monitored before using the lake water as a drinking water resource.

Merschel, Gila; Baldewein, Linda; Bau, Michael; Dantas, Elton Luiz; Walde, Detlef; Bühn, Bernhard

2014-05-01

324

Rare earth element and uranium-thorium variations in tufa deposits from the Mono Basin, CA  

NASA Astrophysics Data System (ADS)

Samples of fossil tufa deposits from several localities in the Mono Basin, eastern California, were analyzed for trace element concentrations in order to better understand changes in lake composition in the past. These deposits were formed during the last glacial cycle, mostly during deglaciation (Benson et al., 1990, PPP). Three elevations are represented by the analyses. Samples from near Highway 167 were sampled between 2063 and 2069 m asl. Samples from near Thompson Road were sampled between 2015 and 2021 m. One layered mound was sampled at 1955 m. Concentrations of the lanthanide rare earth elements (REE), in particular the heavy/light (HREE/LREE) distributions, have been shown to be sensitive to alkalinity in modern saline lakes (e.g., Johannesson et al., 1994, GRL, 21, 773-776), and the same has been suggested for U/Th (Anderson et al., 1982, Science, 216, 514-516). Holocene to near-modern tufa towers exist in shallow water and around the current shoreline (1945 m). Tufa towers above 2000 m include a characteristic morphology termed thinolite, interpreted to represent pseudomorphs after the very cold water mineral ikaite. Most lower elevation towers do not have the thinolite morphology, but some layered tufa mounds at low elevations include several layers of thinolite, such as the one sampled for this project. Analyses were made on millimeter-scale bulk samples from tufa towers. Measurements were made on sample solutions with a Varian 820MS quadrupole ICP-MS. Mono Basin tufa samples have total REE concentrations ranging from 0.029 to 0.77 times average shales. Samples have flat to moderately HREE-enriched shale-normalized patterns with limited overall variability ([La/Lu]SN of 1.8 to 9.6) but with some variability in the slope of the HREE portion of the patterns. Tufa towers sampled from three elevations have (Gd/Lu)SN of 0.40 to 1.5. The REE patterns of most samples have small positive Ce anomalies, but a minority of samples, all from the layered tufa mound, have small negative Ce anomalies. Concentrations of U and Th range from 0.5 to 12 ppm and from 0.2 to 12 ppm, respectively, with substantial variability in U/Th (0.08 to 20). Relative to modern Mono Lake water (Johannesson and Lyons, 1994, Limn. Oc., 39, 1141-1154) the tufa samples have 29 to 144000 times the total REE contents, but the water has HREE/LREE nearly twice as high as the most HREE-enriched fossil tufa. There is a general trend in which samples from higher elevation have lower average total REE, (Gd/Lu)SN and Th and higher average U and U/Th, the latter ranging from 0.52 in the locality at lowest elevation to 10.5 at the highest. In general the results show promise for the application of this approach to paleo-alkalinity, although analyses of modern precipitates as well as laboratory precipitation experiments are needed to fully address the processes.

Wilcox, E. S.; Tomascak, P. B.; Hemming, N.; Hemming, S. R.; Rasbury, T.; Stine, S.; Zimmerman, S. R.

2009-12-01

325

Surface Kinetic Model for the Fractionation of Trace Elements and Isotopes in Calcite Precipitated from Aqueous Solution  

NASA Astrophysics Data System (ADS)

The isotopic and trace element concentrations in calcite and other carbonate minerals form the basis for several paleoceanographic and paleoenvironmental indicators. The chemical and isotopic composition of natural calcites is determined by a combination of equilibrium partitioning and kinetic fractionations. Currently there is no general model that describes when equilibrium applies and how kinetic effects depend on the circumstances and rates of mineral growth. A useful approach is to separate the growth of calcite from aqueous solutions into forward (f) and backward (b) reactions, and to consider the mechanisms and fractionations that may be associated with each. We are evaluating a model where the net precipitation rate of calcite (Rp) is expressed as the difference between a forward rate (Rf) and a backward (dissolution) rate (Rb). Dissolution is approached only as Rp/Rb->0. Much natural calcite, including biogenic, forms under conditions where Rp ? Rb, hence the isotopic and trace element partitioning is strongly influenced by the kinetics of the forward reaction. Assuming that there are kinetic fractionations associated with the forward and backward reactions, a simple model can be developed for the dependence of calcite composition on precipitation rate. This model can explain most available experimental data on Ca and O isotopes, as well as Sr/Ca and Mn/Ca in calcite, and can be used to infer the behavior of other trace and minor elements. The critical parameter in applying the model is the value of Rb which to first order can be estimated from mineral dissolution rates, but apparently is not a constant, but instead varies with solution chemistry, especially at saturation conditions close to equilibrium. The surface kinetic model requires three parameters that are measureable experimentally and potentially also predictable from molecular dynamics simulation approaches. In this way it differs from the surface entrapment model of Watson (2004) which requires six parameters that cannot be independently measured. The next step in understanding the controls on calcite chemistry is to investigate the dependence of Rb (i.e., the surface molecular exchange rate) on precipitation conditions and mechanisms, and to quantify the interplay between the presence of impurities in calcite and the exchange rate. These issues are being addressed with a combination of experiments, studies of natural systems, and MD simulations.

Depaolo, D. J.; Ryerson, F. J.; Watkins, J. M.; Bourg, I. C.; Yang, W.; Nielsen, L. C.; Druhan, J. L.

2010-12-01

326

Extraction processes and solvents for recovery of cesium, strontium, rare earth elements, technetium and actinides from liquid radioactive waste  

DOEpatents

Cesium and strontium are extracted from aqueous acidic radioactive waste containing rare earth elements, technetium and actinides, by contacting the waste with a composition of a complex organoboron compound and polyethylene glycol in an organofluorine diluent mixture. In a preferred embodiment the complex organoboron compound is chlorinated cobalt dicarbollide, the polyethylene glycol has the formula RC.sub.6 H.sub.4 (OCH.sub.2 CH.sub.2).sub.n OH, and the organofluorine diluent is a mixture of bis-tetrafluoropropyl ether of diethylene glycol with at least one of bis-tetrafluoropropyl ether of ethylene glycol and bis-tetrafluoropropyl formal. The rare earths, technetium and the actinides (especially uranium, plutonium and americium), are extracted from the aqueous phase using a phosphine oxide in a hydrocarbon diluent, and reextracted from the resulting organic phase into an aqueous phase by using a suitable strip reagent.

Zaitsev, Boris N. (St. Petersburg, RU); Esimantovskiy, Vyacheslav M. (St. Petersburg, RU); Lazarev, Leonard N. (St. Petersburg, RU); Dzekun, Evgeniy G. (Ozersk, RU); Romanovskiy, Valeriy N. (St. Petersburg, RU); Todd, Terry A. (Aberdeen, ID); Brewer, Ken N. (Arco, ID); Herbst, Ronald S. (Idaho Falls, ID); Law, Jack D. (Pocatello, ID)

2001-01-01

327

Effects of Rare Earth Elements on the Growth of Arnebia euchroma Cells and the Biosynthesis of Shikonin  

Microsoft Academic Search

Nd3+, La3+ and Ce3+ at proper concentrations had positive effects on the cell growth of Arnebia euchroma and production of shikonin derivatives. A mixture of rare earth elements (MRE, La2O3:CeO2:Pr6O11: Sm2O3 = 255:175:3:1, mol\\/mol) behaved the most remarkable effects. Two-stage culture was used for the cell proliferation and the\\u000a biosynthesis of shikonin derivatives. After 20 days culture, 0.05 mM MRE gave the highest cell biomass

Feng Ge; Xiaodong Wang; Bing Zhao; Yuchun Wang

2006-01-01

328

Origin and Evolution of Life: Endless Ordering of the Earth's Light Elements  

Microsoft Academic Search

The evolution of a living organism, as well as pre-biotic molecular evolution, seems to be incon- sistent with the second law of thermodynamics. When a bacterium is compared with some other higher organism, it is clear that all evolution tends to order more and larger molecules into more complex systems. The trick is the radiation of heat from the Earth.

Hiromoto Nakazawa

2007-01-01

329

Mixing rare earth elements with manures to control phosphorus loss in runoff and track manure fate  

Technology Transfer Automated Retrieval System (TEKTRAN)

Concern over the enrichment of agricultural runoff with phosphorus (P) from land applied livestock manures has prompted the development of manure amendments that minimize P solubility. We evaluated the effect of mixing two rare earth chlorides, lanthanum chloride and ytterbium chloride, with poultr...

330

13.21 Geochemistry of the Rare-Earth Element, Nb, Ta, Hf, and Zr Deposits RL Linnen, University of Western Ontario, London, ON, Canada  

E-print Network

13.21 Geochemistry of the Rare-Earth Element, Nb, Ta, Hf, and Zr Deposits RL Linnen, University of rare metals in natural fluids 551 13.21.2.2.2 Aqueous complexation and mineral solubility 552 13 Acknowledgments 564 References 564 13.21.1 Introduction Rare-element mineral deposits, also called rare-metal

Chakhmouradian, Anton

331

Rare Earth Element Mapping of Garnet by Laser Ablation ICP-MS  

NASA Astrophysics Data System (ADS)

The introduction of the electron microprobe brought tremendous advancement to our understanding of mineral forming reactions, thermobarometry and the patterns and controls of major element zoning. Today, the application of laser ablation ICP-MS (LA-ICP-MS) is providing the same advancements, but at the trace element scale. While considerable attention has been paid to the behavior of trace elements in a crystal-melt system, the number of studies addressing trace elements in metamorphic minerals is few. We have developed methods using LA-ICP-MS to rapidly construct quantitative trace element maps of geologic (minerals, corals, coal, etc.) and non-geologic (tree rings, sheep horns, fish scales, metals, etc.) materials. Experimental determination of trace element partitioning and the parameters that control it are determined almost exclusively on experimental melt products and natural glasses. With this study we demonstrate that insight into the behavior of the trace elements during metamorphic mineral growth is now readily obtainable. Garnets from the Nason terrane, North Cascades, WA, USA have been analyzed in order to study trace element heterogeneity. In the Nason terrane, almandine-rich garnets in amphibolite facies rocks all possess distinct enhanced HREE compatibility in the cores with varying degrees of complex zoning towards the rim. A distinct trace-element-enriched annulus is present in nearly all garnets studied. Annuli enriched in the HREEs and Y are common, but annuli enriched only in the LREEs are also present. We suggest the annuli are the result of the breakdown of REE-rich minerals such as monazite, apatite and/or xenotime. The HREE zoning patterns from rim to core can be used to model the changing mechanism for growth zoning. While it is clear that various mechanisms operate during the entire growth history, it appears that intercrystalline diffusion is the dominant mechanism producing HREE zoning in the early stages of garnet growth.

Koenig, A. E.; Koenig, A. E.; Magloughlin, J. F.; Ridley, W. I.

2001-12-01

332

Mass fractions of 52 trace elements and zinc/trace element content ratios in intact human prostates investigated by inductively coupled plasma mass spectrometry.  

PubMed

Contents of 52 trace elements in intact prostate of 64 apparently healthy 13-60-year-old men (mean age 36.5 years) were investigated by inductively coupled plasma mass spectrometry. Mean values (M ± S??) for mass fraction (in milligrams per kilogram, on dry-weight basis) of trace elements were as follows: Ag 0.041 ± 0.005, Al 36 ± 4, Au 0.0039 ± 0.0007, B 0.97 ± 0.13, Be 0.00099 ± 0.00006, Bi 0.021 ± 0.008, Br 29 ± 3, Cd 0.78 ± 0.09, Ce 0.028 ± 0.004, Co 0.035 ± 0.003, Cs 0.034 ± 0.003, Dy 0.0031 ± 0.0005, Er 0.0018 ± 0.0004, Gd 0.0030 ± 0.0005, Hg 0.046 ± 0.006, Ho 0.00056 ± 0.00008, La 0.074 ± 0.015, Li 0.040 ± 0.004, Mn 1.53 ± 0.09, Mo 0.30 ± 0.03, Nb 0.0051 ± 0.0009, Nd 0.013 ± 0.002, Ni 4.3 ± 0.7, Pb 1.8 ± 0.4, Pr 0.0033 ± 0.0004, Rb 15.9 ± 0.6, Sb 0.040 ± 0.005, Se 0.73 ± 0.03, Sm 0.0027 ± 0.0004, Sn 0.25 ± 0.05, Tb 0.00043 ± 0.00009, Th 0.0024 ± 0.0005, Tl 0.0014 ± 0.0001, Tm 0.00030 ± 0.00006, U 0.0049 ± 0.0014, Y 0.019 ± 0.003, Yb 0.0015 ± 0.0002, Zn 782 ± 97, and Zr 0.044 ± 0.009, respectively. The upper limit of mean contents of As, Cr, Eu, Ga, Hf, Ir, Lu, Pd, Pt, Re, Ta, and Ti were the following: As ? 0.018, Cr ? 0.64, Eu ? 0.0006, Ga ? 0.08, Hf ? 0.02, Ir ? 0.0004, Lu ? 0.00028, Pd ? 0.007, Pt ? 0.0009, Re ? 0.0015, Ta ? 0.005, and Ti ? 2.6. In all prostate samples, the content of Te was under detection limit (<0.003). Additionally, ratios of the Zn content to other trace element contents as well as correlations between Zn and trace elements were calculated. Our data indicate that the human prostate accumulates such trace elements as Al, Au, B, Br, Cd, Cr, Ga, Li, Mn, Ni, Pb, U, and Zn. No special relationship between Zn and other trace elements was found. PMID:22549701

Zaichick, Sofia; Zaichick, Vladimir; Nosenko, Sergey; Moskvina, Irina

2012-11-01

333

Geochemistry of rare-earth elements in spinel lherzolites of mantle nodules - A model of the primitive mantle  

NASA Astrophysics Data System (ADS)

Data obtained by Stosch (1986) on the geochemistry of REEs in spinel lherzolites of mineral nodules from alkaline basaltoids of the Shavaryn-Tsaram feature in Central Mongolia were used to construct a model for primitive-mantle geochemistry compatible with the obtained distribution of petrogenic and rare-earth elements. It is pointed out that a petrochemically primitive mantle taking no account of an alkaline basal 'contaminant' is depleted with respect to light REE; for primitive compositions, i.e., close to the REE in chondrites, the presence of small amounts of accessory apatite or primary alkaline basal contaminant is necessary. It is pointed out that these phases can be lost easily in the procedure of cleaning the rocks from the contaminant or in the course of a natural deposition of minerals in the earth mantle. It is concluded that correlations of REE with the CaO found in spinel lherzolites of the earth mantle can be explained within the framework of a model of partial melting of primitive (in terms of REE) apatite-bearing mantle, taking into account an extraction from it of the picrite melt.

Kovalenko, V. I.; Riabchikov, I. D.; Stosch, H.-G.

1989-06-01

334

Speciation of rare earth elements in natural terrestrial waters: assessing the role of dissolved organic matter from the modeling approach  

NASA Astrophysics Data System (ADS)

Humic Ion-Binding Model V, which focuses on metal complexation with humic and fulvic acids, was modified to assess the role of dissolved natural organic matter in the speciation of rare earth elements (REEs) in natural terrestrial waters. Intrinsic equilibrium constants for cation-proton exchange with humic substances (i.e., p KMHA for type A sites, consisting mainly of carboxylic acids), required by the model for each REE, were initially estimated using linear free-energy relationships between the first hydrolysis constants and stability constants for REE metal complexation with lactic and acetic acid. p KMHA values were further refined by comparison of calculated Model V "fits" to published data sets describing complexation of Eu, Tb, and Dy with humic substances. A subroutine that allows for the simultaneous evaluation of REE complexation with inorganic ligands (e.g., Cl -, F -, OH -, SO 42-, CO 32-, PO 43-), incorporating recently determined stability constants for REE complexes with these ligands, was also linked to Model V. Humic Ion-Binding Model V's ability to predict REE speciation with natural organic matter in natural waters was evaluated by comparing model results to "speciation" data determined previously with ultrafiltration techniques (i.e., organic acid-rich waters of the Nsimi-Zoetele catchment, Cameroon; dilute, circumneutral-pH waters of the Tamagawa River, Japan, and the Kalix River, northern Sweden). The model predictions compare well with the ultrafiltration studies, especially for the heavy REEs in circumneutral-pH river waters. Subsequent application of the model to world average river water predicts that organic matter complexes are the dominant form of dissolved REEs in bulk river waters draining the continents. Holding major solute, minor solute, and REE concentrations of world average river water constant while varying pH, the model suggests that organic matter complexes would dominate La, Eu, and Lu speciation within the pH ranges of 5.4 to 7.9, 4.8 to 7.3, and 4.9 to 6.9, respectively. For acidic waters, the model predicts that the free metal ion (Ln 3+) and sulfate complexes (LnSO 4+) dominate, whereas in alkaline waters, carbonate complexes (LnCO 3+ + Ln[CO 3] 2-) are predicted to out-compete humic substances for dissolved REEs. Application of the modified Model V to a "model" groundwater suggests that natural organic matter complexes of REEs are insignificant. However, groundwaters with higher dissolved organic carbon concentrations than the "model" groundwater (i.e., >0.7 mg/L) would exhibit greater fractions of each REE complexed with organic matter. Sensitively analysis indicates that increasing ionic strength can weaken humate-REE interactions, and increasing the concentration of competitive cations such as Fe(III) and Al can lead to a decrease in the amount of REEs bound to dissolved organic matter.

Tang, Jianwu; Johannesson, Karen H.

2003-07-01

335

Halogen and phosphorus storage in the earth. [elemental spatial distribution from geochemical, geophysical, and cosmochemical factors  

NASA Technical Reports Server (NTRS)

Chemical analyses of surface reservoirs, coupled with compositions for interior zones inferred from geophysical and geochemical data have been used to obtain a range of estimates of the bulk composition of the earth. It is suggested that (1) apatite with 3 wt% Fe, up to 1 wt% Cl, and 0.003 wt% Br is the principal mineral reservoir for halogens, and mica is a subsidiary reservoir; (2) apatite with 18 wt% P is the principal store of P in the upper mantle and perhaps lower mantle, but accounts for only one-twentieth of P in the earth; and (3) the remaining P is in a reservoir inaccessible to magmatism, and may amount to a maximum of 0.7 wt% in the core.

Smith, J. V.

1981-01-01

336

Species and distribution of rare earth elements in the Baotou section of the Yellow River in China.  

PubMed

This paper analyses the contents and species distributions of rare earth elements (REEs) in the water-suspended particulate-sediment system of the Baotou section of the Yellow River, China, with known anthropogenic REE input from industrial discharges. The major forms of REEs were suspended and dissolved in the mainstream and the tributaries of the Baotou section, respectively. The concentrations of the dissolved and suspended REEs had the same trends in the overlying water along the mainstream, which increased from the Seqi section (site A) to the mouth of the Sidaosha River (site D), reaching a maximum value at site D, and tending to decrease thereafter. The contents of REEs in sediment cores showed enrichment with light rare earth elements (LREEs). The bound to carbonates and to Fe-Mn oxides are the major forms of REE in the secondary phase and the REE exhibited LREE enrichment pattern and moderate Eu depletion in suspended particulates and surface sediments. The contents and species distributions of REEs in the water-suspended particulate-sediment system of the Baotou section suggest that the anthropogenic source of REEs from Baotou city have enhanced REE accumulation to the Baotou section. This information is important for predicting possible pollution resulting from anthropogenic REE input into rivers. PMID:19495997

He, Jiang; Lü, Chang-Wei; Xue, Hong-Xi; Liang, Ying; Bai, Saruli; Sun, Ying; Shen, Li-Li; Mi, Na; Fan, Qing-Yun

2010-02-01

337

Geochemical studies of rare earth elements in the Portuguese pyrite belt, and geologic and geochemical controls on gold distribution  

USGS Publications Warehouse

This report describes geochemical and geological studies which were conducted by the U.S. Geological Survey (USGS) and the Servicos Geologicos de Portugal (SPG) in the Portuguese pyrite belt (PPB) in southern Portugal. The studies included rare earth element (REE) distributions and geological and geochemical controls on the distribution of gold. Rare earth element distributions were determined in representative samples of the volcanic rocks from five west-trending sub-belts of the PPB in order to test the usefulness of REE as a tool for the correlation of volcanic events, and to determine their mobility and application as hydrothermal tracers. REE distributions in felsic volcanic rocks show increases in the relative abundances of heavy REE and a decrease in La/Yb ratios from north to south in the Portuguese pyrite belt. Anomalous amounts of gold are distributed in and near massive and disseminated sulfide deposits in the PPB. Gold is closely associated with copper in the middle and lower parts of the deposits. Weakly anomalous concentrations of gold were noted in exhalative sedimentary rocks that are stratigraphically above massive sulfide deposits in a distal manganiferous facies, whereas anomalously low concentrations were detected in the barite-rich, proximal-facies exhalites. Altered and pyritic felsic volcanic rocks locally contain highly anomalous concentrations of gold, suggesting that disseminated sulfide deposits and the non-ore parts of massive sulfide deposits should be evaluated for their gold potential.

Grimes, David J.; Earhart, Robert L.; de Carvalho, Delfim; Oliveira, Vitor; Oliveira, Jose T.; Castro, Paulo

1998-01-01

338

Microstructural characteristics of laser clad coatings with rare earth metal elements  

Microsoft Academic Search

The microstructural characteristics of laser clad nickel-based alloy coatings with rare earth (RE) oxide CeO2 or La2O3 were investigated. Nickel-based alloy powder with different contents of CeO2 or La2O3 was laser clad onto a steel substrate. The clad coatings were examined and tested for microstructural features, chemical compositions and phase structure of the clad coatings. A scanning electron microscope (SEM)

K. L. Wang; Q. B. Zhang; M. L. Sun; X. G. Wei

2003-01-01

339

Microstructure and corrosion resistance of laser clad coatings with rare earth elements  

Microsoft Academic Search

The effects of rare earth oxides CeO2 and La2O3 on the microstructure and corrosion resistance of laser clad nickel-based alloy coatings were investigated. The nickel-based alloy powder with CeO2 or La2O3 was laser clad on to a steel substrate. The coatings were examined for microstructural features, compositions, phase structure and corrosion resistance. The results were compared with those for coatings

K. L. Wang; Q. B. Zhang; M. L. Sun; X. G. Wei; Y. M. Zhu

2001-01-01

340

Rare earth elements modification of laser-clad nickel-based alloy coatings  

Microsoft Academic Search

The effects of rare earth oxide CeO2 and La2O3 on the microstructure and wear resistance of laser-clad nickel-based alloy coatings were investigated. The nickel-based alloy powders with different contents of CeO2 or La2O3 were laser-clad on to a steel substrate. The coatings were examined and tested for microstructural features, compositions, phase structure, and wear resistance. The results were compared with

K. L Wang; Q. B Zhang; M. L Sun; X. G Wei; Y. M Zhu

2001-01-01

341

Spectral-finite element approach to three-dimensional electromagnetic induction in a spherical earth  

Microsoft Academic Search

We present a spectral-finite element approach to the forward problem of 3-Dglobal-scale electromagnetic induction in a heterogeneous conducting sphere excited by an external source current. It represents an alternative to a variety of numerical methods for 3-D global-scale electromagnetic induction modelling developed recently (the perturbation expansion approach and the finite element and finite difference schemes). Two possible formulations of electromagnetic

Zdenek Martinec

1999-01-01

342

(Data in metric tons of yttrium oxide (Y O ) content, unless otherwise noted)2 3 Domestic Production and Use: The rare-earth element, yttrium, was mined by one company as a constituent of the  

E-print Network

.20.0000 Free Free. Rare-earth metals, scandium and yttrium, whether or not intermixed or interalloyed 2805 Domestic Production and Use: The rare-earth element, yttrium, was mined by one company as a constituent of the mineral bastnasite, but was not recovered as a separate element during processing. Bastnasite, a rare-earth

343

(Data in metric tons of yttrium oxide (Y2O3) content, unless noted) Domestic Production and Use: The rare-earth element, yttrium, was mined by one company as a constituent of the  

E-print Network

ores and concentrates (monazite) 2612.20.0000 Free Free. Rare-earth metals, scandium and yttrium Production and Use: The rare-earth element, yttrium, was mined by one company as a constituent of the mineral bastnasite, but was not recovered as a separate element during processing. Bastnasite, a rare-earth

344

(Data in metric tons of yttrium oxide (Y2O3) content, unless otherwise noted) Domestic Production and Use: The rare-earth element yttrium was mined as a constituent of the mineral bastnasite,  

E-print Network

and concentrates (monazite) 2612.20.0000 Free. Rare-earth metals, scandium and yttrium, whether or not intermixed Production and Use: The rare-earth element yttrium was mined as a constituent of the mineral bastnasite, but was not recovered as a separate element during processing. Bastnasite, a rare-earth fluocarbonate mineral, was mined

345

(Data in metric tons of yttrium oxide (Y2O3) content, unless otherwise noted) Domestic Production and Use: The rare-earth element, yttrium, was mined as a constituent of the mineral  

E-print Network

.20.0000 Free. Rare-earth metals, scandium and yttrium, whether or not intermixed or interalloyed 2805.30.0000 5 Production and Use: The rare-earth element, yttrium, was mined as a constituent of the mineral bastnasite, but was not recovered as a separate element during processing. Bastnasite, a rare-earth fluocarbonate mineral, was mined

346

(Data in metric tons of yttrium oxide (Y O ) content, unless otherwise noted)2 3 Domestic Production and Use: The rare-earth element, yttrium, was mined by one company as a constituent of the  

E-print Network

/31/96 Thorium ores and concentrates (monazite) 2612.20.0000 Free Free. Rare-earth metals, scandium and yttrium Domestic Production and Use: The rare-earth element, yttrium, was mined by one company as a constituent of the mineral bastnasite, but was not recovered as a separate element during processing. Bastnasite, a rare-earth

347

(Data in metric tons of yttrium oxide (Y O ) content, unless otherwise noted)2 3 Domestic Production and Use: The rare-earth element, yttrium, was mined as a constituent of the mineral bastnasite,  

E-print Network

/31/98 Thorium ores and concentrates (monazite) 2612.20.0000 Free Free. Rare-earth metals, scandium and yttrium Domestic Production and Use: The rare-earth element, yttrium, was mined as a constituent of the mineral bastnasite, but was not recovered as a separate element during processing. Bastnasite, a rare-earth

348

Partitioning of high field-strength and rare-earth elements between amphibole and quartz-dioritic to tonalitic melts: an experimental study  

Microsoft Academic Search

The knowledge of rare-earth element (REE) and high field-strength element (HFSE) partitioning between minerals such as amphibole, pyroxenes or garnet and tonalitic liquids is essential to understand where and how tonalitic melts are generated. In this paper we present the results of trace-element partitioning studies between amphibole and quartz-dioritic to tonalitic liquids which have been conducted at 1 GPa and

M Klein; H.-G Stosch; H. A Seck

1997-01-01

349

The surface sediment types and their rare earth element characteristics from the continental shelf of the northern south China sea  

NASA Astrophysics Data System (ADS)

The grain size as well as some major and trace elements, including rare earth element (REE), for 273 surface sediment samples collected from the continental shelf of the northern South China Sea were analyzed in this study. The sediment types are mainly sandy silt and silt, making up 60% of the whole samples, and secondly are mud, sandy mud, muddy sand and silty sand, making up 28% of the whole samples, based on grain-size in which the Folk's classification was used. The total REE content (?REE) show a wide variation from 21 ppm to 244 ppm with an average value of 155 ppm, which similar to the average ?REE of the China loess, but much different from that in deep-sea clay, showing a significant terrigenous succession. The REE contents in different sediment types vary greatly, mainly enriching in silt, sandy silt, mud and sandy mud. The REE distribution contours parallel to the coastal, presenting like strips and their contents gradually reduce with increasing distance from the coast. The high content of the western Pearl River Mouth, Shang/Xiachuan Islands and Hailing Bay might be regarded to the coastal current developed from the east to the west along to the Pearl River Mouth in the northern South China Sea. But the chondrite-normalized REE patterns in various sediment types have no difference, basically same as those of coastal rivers and upper crust. They all show relative enrichments in light rare earth element (LREE), noticeable negative Eu anomaly and no Ce anomaly, indicating that those sediments are terrigenous sediments and from the same source region. Further analysis suggest that the sedimentary environment in the study area is relatively stable and granite widely distributed in the South China mainland is the main source of REE, which are transported mainly by the Pearl River. The late diagenesis has little effect on the REE.

Wang, Shuhong; Zhang, Nan; Chen, Han; Li, Liang; Yan, Wen

2014-10-01

350

Study of Defects That Trap Excitons in Yttrium Aluminum Garnets Doped With Rare-Earth Elements  

NASA Astrophysics Data System (ADS)

Excitons play a fundamental role in transporting energy in photonic materials. Understanding and controlling excitons dynamics through their interactions with activating impurities and lattice defects is key to improving scintillation and optical properties. Singles crystals of yttrium aluminum garnet (YAG) crystals doped with rare-earths were studied by positron annihilation, thermolunuinescence and optical spectroscopy. Evidence of defect complexes was found in the YAG structure. Positron lifetime measurements were performed to characterize those defects. Effects of dopants on the optical properties and lattice defects were investigated.

Selim, Farida; Varnery, Chris; Collins, Gary; McKay, David; Reda, Sherif

2011-03-01

351

On the determination of the long period tidal perturbations in the elements of artificial earth satellites  

NASA Technical Reports Server (NTRS)

The magnitude of the tidal effects depends upon the elastic properties of the earth as described by Love numbers. The Love numbers appear as the coefficients in the expansion of the exterior tidal potential in terms of spherical harmonics (in Maxwellian form). A single averaging process was performed only along the parallels of latitude. This process preserves additional long period tidal effects (with periods of a few days or more). It also eliminates the short period effects with periods of one day or less.

Musen, P.; Felsentreger, T.

1972-01-01

352

Photoelectron emission analysis of surface elements of the International Sun Earth Explorer  

NASA Technical Reports Server (NTRS)

The photoemission was measured of engineering materials (aluminum; copper, plain; copper, abraded; copper-beryllium; magnesium; silver; In2O3 on silica; reflective coating on silica; teflon; kapton; and Pyre ML) associated with the International Sun Earth Explorer (ISEE) Satellite. The procedures used are described, including the experimental equipment; results of the program, the conclusions reached, and areas for further work are presented. Data regarding the measured yield of the 11 materials whose surface emission was determined is included in the form of plots of photoelectric yield versus incident light wavelength.

Spencer, W. T.

1975-01-01

353

The effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern Cascadia accretionary margin  

USGS Publications Warehouse

Analytical challenges in obtaining high quality measurements of rare earth elements (REEs) from small pore fluid volumes have limited the application of REEs as deep fluid geochemical tracers. Using a recently developed analytical technique, we analyzed REEs from pore fluids collected from Sites U1325 and U1329, drilled on the northern Cascadia margin during the Integrated Ocean Drilling Program (IODP) Expedition 311, to investigate the REE behavior during diagenesis and their utility as tracers of deep fluid migration. These sites were selected because they represent contrasting settings on an accretionary margin: a ponded basin at the toe of the margin, and the landward Tofino Basin near the shelf's edge. REE concentrations of pore fluid in the methanogenic zone at Sites U1325 and U1329 correlate positively with concentrations of dissolved organic carbon (DOC) and alkalinity. Fractionations across the REE series are driven by preferential complexation of the heavy REEs. Simultaneous enrichment of diagenetic indicators (DOC and alkalinity) and of REEs (in particular the heavy elements Ho to Lu), suggests that the heavy REEs are released during particulate organic carbon (POC) degradation and are subsequently chelated by DOC. REE concentrations are greater at Site U1325, a site where shorter residence times of POC in sulfate-bearing redox zones may enhance REE burial efficiency within sulfidic and methanogenic sediment zones where REE release ensues. Cross-plots of La concentrations versus Cl, Li and Sr delineate a distinct field for the deep fluids (z > 75 mbsf) at Site U1329, and indicate the presence of a fluid not observed at the other sites drilled on the Cascadia margin. Changes in REE patterns, the presence of a positive Eu anomaly, and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous Crescent Terrane, located east of the drilled transect.

Kim, Ji-Hoon; Torres, Marta E.; Haley, Brian A.; Kastner, Miriam; Pohlman, John W.; Riedel, Michael; Lee, Young-Joo

2012-01-01

354

Impulsive penetration of filamentary plasma elements into the magnetospheres of the earth and Jupiter  

Microsoft Academic Search

Assuming that the solar wind plasma is usually nonuniform over distances of 10,000 km or less, it is shown that filamentary plasma elements stretched out from the sun can penetrate impulsively and become engulfed into the magnetosphere. The diamagnetic effects associated with these plasma inhomogeneities are observed in outer magnetospheres and magnetosheaths as dips or directional discontinuities in the magnetic

J. Lemaire

1977-01-01

355

Effects of continental insulation and the partitioning of heat producing elements on the Earth's heat loss  

Microsoft Academic Search

Continental lithosphere influences heat loss by acting as a local insulator to the convecting mantle and by sequestering heat-producing radioactive elements from the mantle. Continental heat production can have a two-part effect since it decreases the amount of internal heat driving convection, which lowers mantle temperature, while also increasing the local insulating effect of continental lithosphere, which raises mantle temperature.

C. M. Cooper; A. Lenardic; L. Moresi

2006-01-01

356

Geochemical variations of rare earth elements in Marcellus shale flowback waters and multiple-source cores in the Appalachian Basin  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) - encompassing the naturally occurring lanthanides, yttrium, and scandium - are potential tracers for subsurface groundwater-brine flows and geochemical processes. Application of these elements as naturally occurring tracers during shale gas development is reliant on accurate quantitation of trace metals in hypersaline brines. We have modified and validated a liquid-liquid technique for extraction and pre-concentration of REE from saline produced waters from shale gas extraction wells with quantitative analysis by ICP-MS. This method was used to analyze time-series samples of Marcellus shale flowback and produced waters. Additionally, the total REE content of core samples of various strata throughout the Appalachian Basin were determined using HF/HNO3 digestion and ICP-MS analysis. A primary goal of the study is to elucidate systematic geochemical variations as a function of location or shale characteristics. Statistical testing will be performed to study temporal variability of inter-element relationships and explore associations between REE abundance and major solution chemistry. The results of these analyses and discussion of their significance will be presented.

Noack, C.; Jain, J.; Hakala, A.; Schroeder, K.; Dzombak, D. A.; Karamalidis, A.

2013-12-01

357

Determination of rare earth elements in seawater by on-line column preconcentration inductively coupled plasma mass spectrometry.  

PubMed

A home made column of commercially available iminodiacetate resin, Muromac A-1 (50-100 mesh) was used to concentrate rare earth elements (REEs) (15 elements: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in seawater. An automated low pressure flow analysis method with on-line column preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) is described for the determination of REEs in seawater. Sample solutions (adjusted to pH of 3.0) passed through the column. After washing the column with water, the adsorbed elements were subsequently eluted into the plasma with 0.7 M nitric acid. Calibration curves were accomplished by means of purified artificial seawater with a sample loading time of 120 s. Detection limits (DLs) of the on-line column preconcentration/ICP-MS by eight replicate operations were between 0.040 and 0.251 pg ml(-1) for REEs in the artificial seawater. The precision was less than 8.9% for REEs and one sample can be processed in 7 min using a 7 ml of sample. The proposed method was applied to determine REEs in coastal seawater of Hiroshima Bay, Japan. PMID:18968856

Hirata, Shizuko; Kajiya, Tasuku; Aihara, Masato; Honda, Kazuto; Shikino, Osamu

2002-12-01

358

Borane and borohydride complexes of the rare-earth elements: synthesis, structures, and butadiene polymerization catalysis.  

PubMed

The reaction of potassium 2,5-bis[N-(2,6-diisopropylphenyl)iminomethyl]pyrrolyl [(dip(2)-pyr)K] with the borohydrides of the larger rare-earth metals, [Ln(BH(4))(3)(thf)(3)] (Ln=La, Nd), afforded the expected products [Ln(BH(4))(2)(dip(2)-pyr)(thf)(2)]. As usual, the trisborohydrides reacted like pseudohalide compounds forming KBH(4) as a by-product. To compare the reactivity with the analogous halides, the dimeric neodymium complex [NdCl(2)(dip(2)-pyr)(thf)](2) was prepared by reaction of [(dip(2)-pyr)K] with anhydrous NdCl(3). Reaction of [(dip(2)-pyr)K] with the borohydrides of the smaller rare-earth metals, [Sc(BH(4))(3)(thf)(2)] and [Lu(BH(4))(3)(thf)(3)], resulted in a redox reaction of the BH(4) (-) group with one of the Schiff base functions of the ligand. In the resulting products, [Ln(BH(4)){(dip)(dip-BH(3))-pyr}(thf)(2)] (Ln=Sc, Lu), a dinegatively charged ligand with a new amido function, a Schiff base, and the pyrrolyl function is bound to the metal atom. The by-product of the reaction of the BH(4) (-) anion with the Schiff base function (a BH(3) molecule) is trapped in a unique reaction mode in the coordination sphere of the metal complex. The BH(3) molecule coordinates in an eta(2) fashion to the metal atom. The rare-earth-metal atoms are surrounded by the eta(2)-coordinated BH(3) molecule, the eta(3)-coordinated BH(4) (-) anion, two THF molecules, and the nitrogen atoms from the Schiff base and the pyrrolyl function. All new compounds were characterized by single-crystal X-ray diffraction. Low-temperature X-ray diffraction data at 6 K were collected to locate the hydrogen atoms of [Lu(BH(4)){(dip)(dip-BH(3))-pyr}(thf)(2)]. The (DIP(2)-pyr)(-) borohydride and chloride complexes of neodymium, [Nd(BH(4))(2)(dip(2)-pyr)(thf)(2)] and [NdCl(2)(dip(2)-pyr)(thf)](2), were also used as Ziegler-Natta catalysts for the polymerization of 1,3-butadiene to yield poly(cis-1,4-butadiene). Very high activities and good cis selectivities were observed by using each of these complexes as a catalyst in the presence of various cocatalyst mixtures. PMID:20397155

Jenter, Jelena; Meyer, Nils; Roesky, Peter W; Thiele, Sven K-H; Eickerling, Georg; Scherer, Wolfgang

2010-05-10

359

Control of interface fracture in silicon nitride ceramics: influence of different rare earth elements  

SciTech Connect

The toughness of self-reinforced silicon nitride ceramics is improved by enhancing crack deflection and crack bridging mechanisms. Both mechanisms rely on the interfacial debonding process between the elongated {Beta}-Si{sub 3}N{sub 4} grains and the intergranular amorphous phases. The various sintering additives used for densification may influence the interfacial debonding process by modifying the thermal and mechanical properties of the intergranular glasses, which will result in different residual thermal expansion mismatch stresses; and the atomic bonding structure across the {Beta}-Si{sub 3}N{sub 4} glass interface. Earlier studies indicated that self-reinforced silicon nitrides sintered with different rare earth additives and/or different Y{sub 2}O{sub 3}:AI{sub 2}0{sub 3} ratios could exhibit different fracture behavior that varied from intergranular to transgranular fracture. No studies have been conducted to investigate the influence of sintering additives on the interfacial fracture in silicon nitride ceramics. Because of the complexity of the material system and the extremely small scale, it is difficult to conduct quantitative analyses on the chemistry and stress states of the intergranular glass phases and to relate the results to the bulk properties. The influence of different sintering additives on the interfacial fracture behavior is assessed using model systems in which {Beta}-Si{sub 3}N{sub 4}whiskers are embedded in SIAIRE (RE: rare-earth) oxynitride glasses. By systematically varying the glass composition, the role of various rare-earth additives on interfacial fracture has been examined. Specifically, four different additives were investigated: Al{sub 2}0{sub 3}, Y{sub 2}0{sub 3}, La{sub 2}O{sub 3}, and Yb{sub 2}O{sub 3}. In addition, applying the results from the model systems, the R- curve behavior of self-reinforced silicon nitride ceramics sintered with different Y{sub 2}0{sub 3}:AI{sub 2}0{sub 3} ratios was characterized.

Sun, E.Y.; Becher, P.F.; Waters, S.B.; Hsueh, Chun-Hway; Plucknett, K.P. [Oak Ridge National Lab., TN (United States); Hoffmann, M.J. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Keramik im Maschinenbau

1996-10-01

360

Some experimentally determined zircon/liquid partition coefficients for the rare earth elements  

NASA Astrophysics Data System (ADS)

Partition coefficients for La, Sm, Ho and Lu (REE) between synthetic zircon and felsic, peralkaline liquid were determined at 800°C and 2 kbar water pressure by adding small amounts of REE to experimental charges and analyzing zircons in the quenched runs with an electron microprobe. The preferred zircon/liquid partition coefficients obtained by this method are: La, 1.4-2.1; Sm, 26-40; Ho, 340+; Lu, 72-126. These results confirm the strong heavy rare earth enrichment discovered by Nagasawa (1970) in zircon separates from dacites and granites, but they also introduce a modification to the supposed zircon/liquid partition coefficient pattern. The heavy REE end of the pattern is concave downward, in qualitative resemblance to some garnet/liquid and hornblende/liquid REE partitioning patterns.

Watson, E. Bruce

1980-06-01

361

Removal of alkaline-earth elements by a carbonate precipitation in a chloride molten salt  

SciTech Connect

Separation of some alkaline-earth chlorides (Sr, Ba) was investigated by using carbonate injection method in LiCl-KCl eutectic and LiCl molten salts. The effects of the injected molar ratio of carbonate([K{sub 2}(or Li{sub 2})CO{sub 3}/Sr(or Ba)Cl{sub 2}]) and the temperature(450-750 deg.) on the conversion ratio of the Sr or Ba carbonate were determined. In addition, the form of the Sr and Ba carbonate resulting from the carbonation reaction with carbonates was identified via XRD and SEM-EDS analysis. In these experiments, the carbonate injection method can remove Sr and Ba chlorides effectively over 99% in both LiCl-KCl eutectic and LiCl molten salt conditions. When Sr and Ba were co-presented in the eutectic molten salt, they were carbonated in a form of Ba{sub 0.5}Sr{sub 0.3}CO{sub 3}. And when Sr was present in LiCl molten salt, it was carbonated in the form of SrCO{sub 3}. Carbonation ratio increased with a decreasing temperature and it was more favorable in the case of a K{sub 2}CO{sub 3} injection than that of Li{sub 2}CO{sub 3}. Based on this experiment, it is postulated that carbonate precipitation method has the potential for removing alkali-earth chlorides from LiCl-KCl eutectic and LiCl molten salts. (authors)

Yung-Zun Cho; In-Tae Kim; Hee-Chui Yang; Hee-Chui Eun; Hwan-Seo Park; Eung-Ho Kim [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of)

2007-07-01

362

Rare earth element systematics of fossil bone revealed by LA-ICPMS analysis  

E-print Network

isotope ratios of their elements (e.g., 2 H/1 H, 13 C/12 C, 15 N/14 N, 18 O/16 O, 34 S/32 S). Isotope/or diet of the organism. The physiological differences between the C3 and C4 photosynthetic pathways result in large differences in the 13 C/12 C values of car- bohydrates, allowing one to trace the flow

Schöne, Bernd R.

363

ANALYTICAL USE OF ARSENAZO. III. DETERMINATION OF THORIUM, ZIRCONIUM, URANIUM AND RARE EARTH ELEMENTS  

Microsoft Academic Search

The reagent arsenazo III (1,8-dihydroxynaphthalene3,6-disulphonic acid-; 2,7-bisSTA(azo-2)-phenylarsonic acid!) gave marked color reactions with a number ; of elements. Anions were found to affect the reaction oniy to a slight degree ; and it is possible to work at low pH values; the reaction is very sensitive and ; the compound was thus used for the photometric determination of Th, Zr,

S Savvin

1961-01-01

364

Venus, Earth, Xenon  

NASA Astrophysics Data System (ADS)

Xenon has been regarded as an important goal of many proposed missions to Venus. This talk is intended to explain why. Despite its being the heaviest gas found in natural planetary atmospheres, there is more evidence that Xe escaped from Earth than for any element apart from helium: (i) Atmospheric Xe is very strongly mass fractionated (at about 4% per amu) from any known solar system source. This suggests fractionating escape that preferentially left the heavy Xe isotopes behind. (ii) Xe is underabundant compared to Kr, a lighter noble gas that is not strongly mass fractionated in air. (iii) Radiogenic Xe is strongly depleted by factors of several to ~100 compared to the quantities expected from radioactive decay of primordial solar system materials. In these respects Xe on Mars is similar to Xe on Earth, but with one key difference: Xe on Mars is readily explained by a simple process like hydrodynamic escape that acts on an initially solar or meteoritic Xe. This is not so for Earth. Earth's Xe cannot be derived by an uncontrived mass fractionating process acting on any known type of Solar System Xe. Earth is a stranger, made from different stuff than any known meteorite or Mars or even the Sun. Who else is in Earth's family? Comets? We know nothing. Father Zeus? Data from Jupiter are good enough to show that jovian Xe is not strongly mass-fractionated but not good enough to determine whether Jupiter resembles the Earth or the Sun. Sister Venus? Noble gas data from Venus are incomplete, with Kr uncertain and Xe unmeasured. Krypton was measured by several instruments on several spacecraft. The reported Kr abundances are discrepant and were once highly controversial. These discrepancies appear to have been not so much resolved as forgotten. Xenon was not detected on Venus. Upper limits were reported for the two most abundant xenon isotopes 129Xe and 132Xe. From the limited data it is not possible to tell whether Venus's affinities lie with the solar wind, or with the chondrites, with Earth, or with none of the above. Modern spacecraft mass spectrometers are at least 100-fold more sensitive to noble gases. Sending such an instrument to Venus may be the last best hope for decrypting what Earth's noble gases have been trying to tell us.

Zahnle, K. J.

2013-12-01

365

Heavy-ion Fractionation in the Impulsive Solar Energetic Particle Event of 2002 August 20: Elements, Isotopes, and Inferred Charge States  

NASA Astrophysics Data System (ADS)

Measurements of heavy-ion elemental and isotopic composition in the energy range ~12-60 MeV nucleon-1 are reported from the Advanced Composition Explorer/Solar Isotope Spectrometer (ACE/SIS) instrument for the solar energetic particle (SEP) event of 2002 August 20. We investigate fractionation in this particularly intense impulsive event by examining the enhancements of elemental and isotopic abundance ratios relative to corresponding values in the solar wind. The elemental enhancement pattern is similar to those in other impulsive events detected by ACE/SIS and in compilations of average impulsive-event composition. For individual elements, the abundance of a heavy isotope (mass M 2) is enhanced relative to that of a lighter isotope (M 1) by a factor ~(M 1/M 2)? with ? ~= -15. Previous studies have reported elemental abundance enhancements organized as a power law in Q/M, the ratio of estimated ionic charge to mass in the material being fractionated. We consider the possibility that a fractionation law of this form could be responsible for the isotopic fractionation as a power law in the mass ratio and then explore the implications it would have for the ionic charge states in the source material. Assuming that carbon is fully stripped (Q C = 6), we infer mean values of the ionic charge during the fractionation process, QZ , for a variety of elements with atomic numbers 7 <= Z <= 28. We find that Q Fe ~= 21-22, comparable to the highest observed values that have been reported at lower energies in impulsive SEP events from direct measurements near 1 AU. The inferred charge states as a function of Z are characterized by several step increases in the number of attached electrons, Z - QZ . We discuss how this step structure, together with the known masses of the elements, might account for a variety of features in the observed pattern of elemental abundance enhancements. We also briefly consider alternative fractionation laws and the relationship between the charge states we infer in the source material and those derived from in situ observations.

Wiedenbeck, M. E.; Cohen, C. M. S.; Leske, R. A.; Mewaldt, R. A.; Cummings, A. C.; Stone, E. C.; von Rosenvinge, T. T.

2010-08-01

366

Laser-excited fluorescence of rare earth elements in fluorite: Initial observations with a laser Raman microprobe  

USGS Publications Warehouse

Fluorescence emission spectra of three samples of fluorite containing 226-867 ppm total rare earth elements (REE) were excited by visible and ultraviolet wavelength lines of an argon ion laser and recorded with a Raman microprobe spectrometer system. Narrow emission lines ( 0.9 for Eu2+ and 0.99 for Er3+. Detection limits for three micrometer spots are about 0.01 ppm Eu2+ and 0.07 ppm Er3+. These limits are less than chondrite abundance for Eu and Er, demonstrating the potential microprobe analytical applications of laser-excited fluorescence of REE in fluorite. However, application of this technique to common rock-forming minerals may be hampered by competition between fluorescence emission and radiationless energy transfer processes involving lattice phonons. ?? 1992.

Burruss, R.C.; Ging, T.G.; Eppinger, R.G.; Samson, a.M.

1992-01-01

367

Tunable magnetic and magnetocaloric properties in heavy rare-earth based metallic glasses through the substitution of similar elements  

NASA Astrophysics Data System (ADS)

The influence of interchangeable substitution of similar heavy rare-earth-elements (HRE), i.e., Gd-Ho, Gd-Er, and Ho-Er, on the magnetic and magnetocaloric properties of HRE55Al27.5Co17.5 metallic glasses was evaluated. The magnetic transition temperature (TC) can be tuned in a wide temperature range from 8 K to 93 K by adjusting the substitutional concentration in the resulting metallic glasses. A roughly linear correlation between peak value of magnetic entropy change (|?SMpk|) and TC-2/3 was obtained in the three systems. This kind of substitutional adjustment provides a useful method for designing desirable candidates in metallic glasses with high magnetic entropy change, large magnetic cooling efficiency, and tunable TC for magnetic refrigerant in nitrogen and hydrogen liquefaction temperature ranges.

Zhang, Huiyan; Li, Ran; Zhang, Leilei; Zhang, Tao

2014-04-01

368

Rare earth element exchange through the Bosporus: The Black Sea as a net source of REEs to the Mediterranean Sea  

SciTech Connect

The Bosporus is the only source of seawater to the Black Sea and helps to maintain the basin-wide salinity gradient that caused the Black Sea to become the largest permanently anoxic basin in the world, some 3000 years ago. Concentrations of dissolved rare earth elements (REEs) in each of the three layers of water that make up the Bosporus inflow/outflow system, substituted into a simple hydrographic model that evaluates the entertainment of outflowing Black Sea water in the inflowing Mediterranean Sea water, suggest that the Black Sea acts as a net source of REEs to the Mediterranean Sea. This holds true for Ce, which shows a considerable range of concentrations in the outflowing Black Sea water, even if the lower end of that range is taken to represent the Ce concentration of the Black Sea endmember.

Schijf, J. [Univ. of Utrecht, Amsterdam (Netherlands); De Baar, J.W. [Netherlands Institute for Sea Research, Den Burg (Netherlands)

1995-09-01

369

Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature  

NASA Astrophysics Data System (ADS)

The effects of heavy rare earth (RE) additions on the Curie temperature (TC) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune TC in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (?SM) and refrigerant capacity (RC) of the alloys. The observed values of ?SM and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd5Ge1.9Si2Fe0.1. The tunable TC and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

Li, Jiawei; Huo, Juntao; Law, Jiayan; Chang, Chuntao; Du, Juan; Man, Qikui; Wang, Xinmin; Li, Run-Wei

2014-08-01

370

Multiple stirred-flow chamber assembly for simultaneous automatic fractionation of trace elements in fly ash samples using a multisyringe-based flow system  

SciTech Connect

There is a current trend in automation of leaching tests for trace elements in solid matrixes by use of flow injection based column approaches. However, as a result of the downscaled dimensions of the analytical manifold and execution of a single extraction at a time, miniaturized flow-through column approaches have merely found applications for periodic investigations of trace element mobility in highly homogeneous environmental solids. A novel flow-based configuration capitalized on stirred-flow cell extraction is proposed in this work for simultaneous fractionation of trace elements in three solid wastes with no limitation of sample amount up to 1.0 g. A two-step sequential extraction scheme involving water and acetic acid (or acetic acid/acetate buffer) is utilized for accurate assessment of readily mobilizable fractions of trace elements in fly ash samples. The W automated extraction system features high tolerance to flow rates ({<=} 6 mL min{sup -1}) and, as opposed to operationally defined batchwise methods, the solid to liquid ratio is not a critical parameter for, determination of overall readily leachable trace elements provided that exhaustive extraction is ensured. Analytical performance of the dynamic extractor is evaluated for fractionation analysis of a real coal fly ash and BCR-176R fly ash certified reference material. No significant differences were found at the 0.05 significance level between summation of leached concentrations in each fraction plus residue and concentration values of BCR-176R, thus revealing the accuracy of the automated method. Overall extractable pools of trace metals in three samples are separated in less than 115 min, even for highly contaminated ashes, versus 18-24 h per fraction in equilibrium leaching tests. The multiple stirred-flow cell assembly is thus suitable for routine risk assessment studies of industrial solid byproduct.

Boonjob, W.; Miro, M.; Cerda, V. [Mahidol University, Bangkok (Thailand). Faculty of Science

2008-10-01

371

Magnetocaloric effect in AlFe2B2: toward magnetic refrigerants from earth-abundant elements.  

PubMed

AlFe2B2 was prepared by two alternative synthetic routes, arc melting and synthesis from Ga flux. In the layered crystal structure, infinite chains of B atoms are connected by Fe atoms into two-dimensional [Fe2B2] slabs that alternate with layers of Al atoms. As expected from the theoretical analysis of electronic band structure, the compound exhibits itinerant ferromagnetism, with the ordering temperature of 307 K. The measurement of magnetocaloric effect (MCE) as a function of applied magnetic field reveals isothermal entropy changes of 4.1 J kg(-1) K(-1) at 2 T and 7.7 J kg(-1) K(-1) at 5 T. These are the largest values observed near room temperature for any metal boride and for any magnetic material of the vast 122 family of layered structures. Importantly, AlFe2B2 represents a rare case of a lightweight material prepared from earth-abundant, benign reactants which exhibits a substantial MCE while not containing any rare-earth elements. PMID:23731263

Tan, Xiaoyan; Chai, Ping; Thompson, Corey M; Shatruk, Michael

2013-06-26

372

Temperature Dependence of Anomalous Paramagnetically Shifted Nuclear Magnetic Resonance Peaks in Iron-Bearing Pyrope and Rare Earth Element Orthophosphates  

NASA Astrophysics Data System (ADS)

Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) has long been used to obtain structural information of geologically important minerals and glasses. The presence of paramagnetic ions such as Fe2+, Fe3+, Co2+, Ni2+, and rare earth elements may lead to “paramagnetically-shifted” NMR peaks. Previous work on 27Al and 29Si NMR on natural pyropes from the Dora Maira massif containing up to 3.5 wt % FeO revealed several anomalous peaks which were well outside the normal range of chemical shifts expected in 27Al and 29Si NMR spectra. We have collected 27Al and 29Si Variable Temperature NMR (VT-NMR) data on these samples and 31P VT-NMR on several synthetic rare earth element orthophosphates. The positions of the anomalous peaks are dependent on the magnetic susceptibility of the neighboring paramagnetic impurity. These peaks therefore have a direct dependence on inverse temperature, in good agreement with the theoretical underpinnings of MAS-NMR on solids containing paramagnetic impurities. VT-NMR data taken together with the observation of a drastic reduction in relaxation times leads to the conclusion that these peaks are caused by interactions with paramagnetic impurities in the cation coordination shells of the nuclei being probed. Further analysis of such peaks in these systems will likely lead to previously unobtainable structural information. Refinement of these techniques for studying paramagnetic impurities in minerals could potentially open up a number of previously inaccessible geological materials to investigation by high-resolution MAS-NMR.

Palke, A.; Stebbins, J. F.; Grandinetti, P.

2009-12-01

373

Determination of trace rare earth elements in gadolinium aluminate by inductively coupled plasma time of flight mass spectrometry  

NASA Astrophysics Data System (ADS)

An analytical methodology was developed for the precise quantification of ten trace rare earth elements (REEs), namely, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, and Tm, in gadolinium aluminate (GdAlO3) employing an ultrasonic nebulizer (USN)-desolvating device based inductively coupled plasma mass spectrometry (ICP-MS). A microwave digestion procedure was optimized for digesting 100 mg of the refractory oxide using a mixture of sulphuric acid (H2SO4), phosphoric acid (H3PO4) and water (H2O) with 1400 W power, 10 min ramp and 60 min hold time. An USN-desolvating sample introduction system was employed to enhance analyte sensitivities by minimizing their oxide ion formation in the plasma. Studies on the effect of various matrix concentrations on the analyte intensities revealed that precise quantification of the analytes was possible with matrix level of 250 mg L- 1. The possibility of using indium as an internal standard was explored and applied to correct for matrix effect and variation in analyte sensitivity under plasma operating conditions. Individual oxide ion formation yields were determined in matrix matched solution and employed for correcting polyatomic interferences of light REE (LREE) oxide ions on the intensities of middle and heavy rare earth elements (MREEs and HREEs). Recoveries of ? 90% were achieved for the analytes employing standard addition technique. Three real samples were analyzed for traces of REEs by the proposed method and cross validated for Eu and Nd by isotope dilution mass spectrometry (IDMS). The results show no significant difference in the values at 95% confidence level. The expanded uncertainty (coverage factor 1?) in the determination of trace REEs in the samples were found to be between 3 and 8%. The instrument detection limits (IDLs) and the method detection limits (MDLs) for the ten REEs lie in the ranges 1-5 ng L- 1 and 7-64 ?g kg- 1 respectively.

Saha, Abhijit; Deb, S. B.; Nagar, B. K.; Saxena, M. K.

374

Siderophore-promoted transfer of rare earth elements and iron from volcanic ash into glacial meltwater, river and ocean water  

NASA Astrophysics Data System (ADS)

The rare earth elements (REE) are a group of trace elements that have short marine residence times and that in river, lake and marine surface waters are typically associated with organic and inorganic particles. Explosive volcanic eruptions, such as the 2010 eruptions of Eyjafjallajökull volcano in Iceland, produce volcanic ash particles which can be an important source of iron and other nutrients for aquatic organisms. To become bioavailable, however, this iron needs to be solubilized by complexing agents, such as siderophores. A well-studied example of such a chelator is the biogenic siderophore desferrioxamin-B (DFOB). Based on results from incubation experiments with glacial meltwater-rich river waters from southern Iceland, which are rich in suspended volcanic ash and that had been incubated with and without DFOB, respectively, we here show that siderophores not only enhance the release of iron, but also promote the mobilization of REE from these particles. In the presence of DFOB, partial dissolution of volcanic ash (and presumably other lithic particles) produces a flux of dissolved REE into ambient waters, that is characterized by depletion of the light REE over the middle REE and by selective enrichment of cerium, due to the formation of dissolved Ce(IV)-DFOB complexes. In siderophore-rich environments, this siderophore-bound REE flux has the potential to modify the concentrations and distribution of the dissolved REE and of the isotopic composition of dissolved Nd in glacial meltwaters, river waters and seawater and might be a component of the boundary effects between shelf sediments and seawater, which are assumed to account for the “missing Nd flux” to seawater. Thermodynamic data further suggest that siderophore-promoted element mobilization could also be important for other polyvalent (trace) elements, such as Hf.

Bau, Michael; Tepe, Nathalie; Mohwinkel, Dennis

2013-02-01

375

Partitioning of Inorganic Elements Consumed by Humans Between the Various Fractions of Human Wastes: A Review and Analysis of Existing Literature  

NASA Technical Reports Server (NTRS)

The nutritional requirements of humans and astronauts are well defined and show consistency, but the same cannot be said of human wastes. Nutrients taken up by humans can be considered to fall into two major categories - organic and inorganic fractions. Carbon, hydrogen, oxygen, nitrogen and sulfur are elements that are associated with the organic fraction. These elements are taken up in large amounts by humans and when metabolized released in wastes often in gaseous forms or as water. On the other hand, a large number of the elements are simply exchanged and can be accounted for in the liquid and solid wastes 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), 17 essential microelements, (e.g. Fe, Mn, Cr, Co, Cu, Zn, Se and Sr). When provided in the recommended concentrations to an adult human, these elements should not normally accumulate in humans, but will be excreted in the different human wastes. Knowledge of the partitioning of these elements between the different human waste fractions is fundamental to understanding (a) how these elements can be recovered for reuse in space habitats, and (b) to developing the processors for waste management. The current literature is exhaustive but sometimes also conflicting. We have used the existing knowledge of nutrition and waste from medical literature and NASA documentation to develop a consensus to typify and chemically characterize the various human wastes. The partitioning of these elements has been developed into a functional model.

Wignarajah, K.; Fisher, John W.; Pisharody, Suresh A.

2003-01-01

376

Annual budget of Gd and related Rare Earth Elements in a river basin heavily disturbed by anthropogenic activities.  

NASA Astrophysics Data System (ADS)

The real environmental impact of micropollutants in river systems can be difficult to assess, essentially due to uncertainties in the estimation of the relative significance of both anthropogenic and natural sources. The natural geochemical background is characterized by important variations at global, regional or local scales. Moreover, elements currently considered to be undisturbed by human activities and used as tracers of continental crust derived material have become more and more involved in industrial or agricultural processes. The global production of lanthanides (REE), used in industry, medicine and agriculture, for instance, has increased exponentially from a few tons in 1950 to projected 185 kt in 2015. Consequently, these new anthropogenic contributions impact the natural cycle of the REE. Gd and related REE are now worldwide recognized as emergent micropollutants in river systems. Nevertheless, there is still a gap concerning their temporal dynamics in rivers and especially the quantification of both the anthropogenic and natural contributions in surface water. The acquisition of such quantitative information is of primordial interest because elements from both origins may present different bioavailability and toxicity levels. Working at the river basin scale allows for quantifying micropollutant fluxes. For this reason, we monitored water quality and discharge of the Alzette River (Luxembourg, Europe) over two complete hydrological cycles (2010-2013). The substantial contamination, is principally due to the steel industry in the basin, which has been active from 1875 until now, and to the related increase of urban areas. The particulate and dissolved fractions of river water were monitored using a multitracer approach (standard parameters for water quality including REE concentrations, Pb, Sr, Nd radiogenic isotopes) with two sampling setups (bi-weekly and flood event based sampling). This extensive sampling design allowed quantifying the annual budget of the REE in the particulate and dissolved fractions of the river water and the waste water treatment plant effluents. Enrichments in Gd have been observed for the dissolved fraction of the water during low water levels. This enrichment has not been detected in the surrounding soils of the basin and can be related to the effluents of the waste water treatment plants, which control the REE chemistry of the dissolved fraction during the low water period. When flood events occur, the Gd anomaly progressively disappears and gives way to the chemical signature of the basin soils. The REE and intense hydrological monitoring we performed at the same time allowed for the annual quantification of the anthropogenic vs. natural REE fluxes in the river water of this heavily polluted basin.

Hissler, Christophe; Stille, Peter; Guignard, Cédric; François Iffly, Jean; Pfister, Laurent

2014-05-01

377

Trace-element evidence for the origin of desert varnish by direct aqueous atmospheric deposition  

E-print Network

, Ni, Pb and the rare-earth elements (REEs). In particular, they have anomalously high Ce/La and low Y Nivedita Thiagarajan, Cin-Ty Aeolus Lee* Department of Earth Science, MS-126, Rice University, Houston, TX elemental fractionations. One remaining possibility is that the Fe, Mn and trace metals in varnish

Lee, Cin-Ty Aeolus

378

Dynamic melting of proterozoic upper mantle: Evidence from rare earth elements in oceanic crust of Eastern Newfoundland  

NASA Astrophysics Data System (ADS)

Rare Earth Element (REE) data confirm earlier suggestions from major and trace elements that the Proterozoic Burin Group in the southwestern Avalon Zone is similar to modern oceanic tholeiites, and also exhibit a systematic evolution through the sequence. The Group forms a 60-km long belt consisting of four formations of pillowed basalt, two of subaqueous volcaniclastic and minor stromatolitic sediments and pyroclastics, and a thick gabbro-quartz diorite sill, with a total thickness of about 5000 m. Basalts of the oldest formation are enriched in light (LREE) with a chondrite-normalized pattern similar to alkali basalts. REE patterns through the rest of the sequence can be matched by those of modern ocean basins, with a steady decrease in total REE and a distinct depletion in LREE at the top of the sequence. REE patterns of the gabbroic sill are similar to those of oceanic gabbros, with LREE depletion and a small positive Eu anomaly. This evolutionary pattern can be interpreted as the result of progressive ‘dynamic’ partial melting and depletion of a single mantle source region.

Strong, D. F.; Dostal, J.

1980-04-01

379

Mineralogical, chemical composition and distribution of rare earth elements in clay-rich sediments from Southeastern Nigeria  

NASA Astrophysics Data System (ADS)

Cretaceous claystone sediments from Enugu, Southeastern, Nigeria were analyzed for their mineralogy and chemistry. Major minerals are quartz and kaolinite while montmorillonite is in minor quantity. The sediments are silica-rich, but showed low values of Al, Fe, Sc and Cr. The values of the chemical index of alteration (CIA) ranged from 89.9 to 94.5 and the values of chemical index of weathering (CIW) ranged from 95.1 to 98.9. Low contents of the alkali and alkali earth elements (Na, K, Mg, Al, Ca) of the clay-rich sediments suggest a relatively more intense weathering of source area. Depleted Ba, Rb, Ca, and Mg suggest that they were probably flushed out by water during sedimentation. The mineralogical composition, REE contents, and elemental ratios in the sediments suggest a provenance from mainly felsic rocks, with only minor contributions from basic sources. Despite intense weathering the REE, Th, and Sc remained in the clays suggesting that they were immobile.

Odoma, A. N.; Obaje, N. G.; Omada, J. I.; Idakwo, S. O.; Erbacher, J.

2015-02-01

380

Partitioning and Leaching Behavior of Actinides and Rare Earth Elements in a Zirconolite- Bearing Hydrothermal Vein System  

SciTech Connect

Chemical extraction techniques and scanning electron microscopy were used to study the distribution and behavior of actinides and rare earth elements (REE) in hydrothermal veins at Adamello (Italy). The six samples discussed in this paper were from the phlogopite zone, which is one of the major vein zones. The samples were similar in their bulk chemical composition, mineralogy, and leaching behavior of major elements (determined by extraction with 9 M HCl). However, there were major differences in the extractability of REE and actinides. The most significant influence on the leaching characteristics appears to be the amounts of U, Th and REE incorporated in resistant host phases (zirconolite and titanite) rather than readily leached phases (such as apatite). Uranium and Th are very highly enriched in zirconolite grains. Actinides were more readily leached from samples with a higher content of U and Th, relative to the amount of zirconium. The results show that REE and actinides present in chemically resistant host minerals can be retained under aggressive leaching conditions. (authors)

Payne, Timothy E.; Hart, Kaye P.; Lumpkin, Gregory R.; McGlinn, Peter J. [Australian Nuclear Science and Technology Organisation, PMB 1, Menai, 2234 (Australia); Giere, Reto [Mineralogisch-Geochemisches Institut, Albert-Ludwigs-Universitaet, Freiburg, D-79104 (Germany)

2007-07-01

381

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  

Microsoft Academic Search

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

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

2010-01-01

382

Visible Light Driven Photoelectrodes Made of Earth Abundant Elements for Water Photoelectrolysis  

NASA Astrophysics Data System (ADS)

With the aim of creating a clean and sustainable energy supply, the direct use of solar energy to produce chemical energy has been pursued for many years. Particularly, the photoelectrolysis of water to generate hydrogen by semiconductor photoelectrodes has attracted great attention because of its advantage of using only water and sunlight, both of which are widely distributed, as raw materials. The earth abundant and visible light absorbing materials are promising for this application for the advantages of easy access and high theoretical solar to hydrogen conversion efficiency. In this thesis, the cadmium sulfide based and copper oxide based photoelectrodes were fabricated and characterized to determine their potential for photoelectrolysis. As one of the semiconductors with relatively narrow band gap, CdS (2.4eV) has a conduction band edge more negative than the water reduction potential level and a valence band edge more positive than the water oxidation potential level, enabling n-type CdS and p-type CdS as good candidates for photoanode and photocathode respectively. CdS thin film with thickness around 2mum was deposited onto Mo back contact on glass, which formed ohmic contact with CdS. The as-prepared CdS was intrinsic n-type due to the easy formation of sulfur vacancies and it was converted to p-type by the controlled thermal diffusion of copper atoms which substituted cadmium to produce acceptor state. The optimal Cu doping level for the interest of water photoelectrolysis was found to be at 5.4% concentration. Cu2O with band gap of 2.0eV is another attracting competitor for the photoelectrode among the metal-oxide semiconductors. Both thin film and highly aligned nanowire arrays Cu2O were prepared by thermal oxidation of Cu film and Cu nanowires on Au substrates synthesized by electrodeposition. Cu2O was found to be p-type because of the copper vacancies. The photocurrent of the Cu2O nanowires photocathode was found to be twice that of the Cu2O film, and the bare Cu2O photocathode suffered from a significant photo-induced reductive decomposition. By modifying the surface of the Cu2O nanowires with protecting layers of CuO and TiO2, direct contact of Cu2O with the electrolyte was avoided, and the Cu2O/CuO/TiO2 coaxial nanocable structures were found to gain 74% higher photocurrent and 4.5 times higher stability. Furthermore, the co-catalysts were also used to modify the photoelectrode surface to reduce the water splitting overpotentials by facilitating the transfer of the photo-induced carriers to the electrolyte. Cobalt based co-catalysts, both the Co2+ and Co3O4 thin film, enhanced the stability of the intrinsic n-CdS photoanode. The Pt modification of CdS:Cu, effectively eliminating the large transient photocurrent, enhanced the photocurrent and stability and positively shifted the onset potential of the cathodic photocurrent by 90 mV, and the hydrogen evolution from the p-type CdS:Cu/Pt photocathode was observed for the first time. This thesis not only studied the water photoelectrolysis potentials of CdS and Cu2O, but also presented general methods to prevent photocorrosion and enhance photo-activity, which could be also applied to other visible light responsive and earth abundant materials to enlarge the range of material choice for solar water splitting

Huang, Qiang

383

Effects of continental insulation and the partitioning of heat producing elements on the Earth's heat loss  

NASA Astrophysics Data System (ADS)

Continental lithosphere influences heat loss by acting as a local insulator to the convecting mantle and by sequestering heat-producing radioactive elements from the mantle. Continental heat production can have a two-part effect since it decreases the amount of internal heat driving convection, which lowers mantle temperature, while also increasing the local insulating effect of continental lithosphere, which raises mantle temperature. We explored these competing effects using simulations that incorporated enriched continents within a mixed internal- and bottom-heated convecting mantle. Increasing continental surface area was found to enhance global heat loss for a range of heat production distributions and Rayleigh numbers. The effect of enriched continents was evident as a double peak in the continental surface area values that maximize global heat loss. That the presence of continental lithosphere could increase average mantle temperature despite the mantle being depleted suggests that continents can significantly influence mantle potential temperature.

Cooper, C. M.; Lenardic, A.; Moresi, L.

2006-07-01

384

Rare earth element patterns as correlation tools and tectonic indicators for the Paleogene Dillon Volcanics, southwestern Montana  

SciTech Connect

The Dillon Volcanics of the Paleogene Renova Formation consist of epiclastic, pyroclastic, and volcanic rocks. The latter are composed of alkaline and transitional basalts and rhyolites. Major and trace element variation diagrams indicate that both rock types had a similar parent magma source, and that the rhyolites were mainly derived from a basaltic parent magma. This is confirmed by very similar rare earth element (REE) patterns. The REE patterns are typical of continental rift zone volcanics, and indicate that bimodal rift zone volcanism occurred in a back-arc setting 30 m.y. before basin-and-range extension. Subsequent normal faulting, combined with Neogene erosion, has separated the dillon Volcanics into isolated outcrops that cannot be accurately correlated in the field. Major and trace element compositional trends are not good correlation tools, but chondrite-normalized REE patterns are almost parallel for the rhyolites and can be used to correlate now-isolated outcrops. REE patterns for the basalts do not show the same degree of similarity, but their patterns do indicate a common magmatic source. REE patterns for continental rift settings typically show enrichment in light REE's, reflecting derivation from a light REE-enriched mantle source such as sub-continental lithosphere. As eruption of the Dillon volcanics was partly contemporaneous with arc volcanism related to the Laramide orogeny, the sub-continental lithosphere may have been enriched in light REE's bu subduction zone fluids derived from the down-going Farallon plate. However, it might not be possible to distinguish continental rift zone volcanics from continental back-arc basin volcanics. The authors favor the latter model because of the chronologic and geographic relationship of the dillon Volcanics with nearby continental arc volcanic fields.

McDowell, R.J.; Fritz, W.J.; Ghazi, A.M. (Georgia State Univ., Atlanta, GA (United States). Dept. of Geology)

1993-04-01

385

Investigation of the separation of scandium and rare earth elements from red mud by use of reversed-phase HPLC.  

PubMed

A chromatographic method has been developed for separation and determination of scandium (Sc) and rare earth elements (REEs) in samples from a red mud (RM)-utilization process. Reversed-phase high-performance liquid chromatography (RP-HPLC) with post-column derivatization using 4-(2-pyridylazo)-resorcinol (PAR) and UV-visible detection at 520 nm was tested using different gradient elution profiles and pH values to optimize separation and recovery, primarily for Sc but also for yttrium and the individual lanthanides, from iron present in the samples. The separation was performed in less than 20 min by use of a mobile phase gradient. The concentration of alpha-hydroxyisobutyric acid ( alpha-HIBA), as eluent, was altered from 0.06 to 0.4 mol L(-1) (pH 3.7) and 0.01 mol L(-1) sodium salt n-octane sulfonic acid (OS) was used as modifier. Very low detection limits in the nanogram range and a good resolution for Sc and REEs except for Y/Dy were achieved. Before application of the method to the red mud samples and to the corresponding bauxites, Sc and REEs were leached from red mud with 0.6 mol L(-1) HNO(3) and mostly separated, as a group, from the main elements by ion exchange/selective elution (6 mol L(-1) HNO(3)) in accordance with a pilot-plant process developed in this laboratory. After evaporation of the eluent to dryness the extracted elements were re-dissolved in the mobile phase. By use of this chromatographic method Sc, which is the most expensive of the elements investigated and occurs in economically interesting concentrations in red mud, could be separated not only from co-existing Fe but also from Y/Dy, Yb, Er, Ho, Gd, Eu, Sm, Nd, Pr, Ce and La. All the elements investigated were individually recovered. Their recoveries were found to be nearly quantitative. PMID:15221192

Tsakanika, Lambrini V; Ochsenkühn-Petropoulou, Maria Th; Mendrinos, Leonidas N

2004-07-01

386