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1

Rare earth element fractionation in magmatic Ca-rich garnets  

NASA Astrophysics Data System (ADS)

Igneous garnets have the potential to strongly fractionate rare earth elements (REE). Yet informations on partition coefficients are very scant, and criteria for distinguishing between hydrothermal and magmatic garnets are ambiguous. To fill this gap, we present trace element and isotopic data for two types of Ca-rich garnets from phonolites (Mt. Somma-Vesuvius). Both Ca-garnet populations are different in their style and dynamics of fractionation: one population is progressively strongly depleted in HREE from core to rim, reflecting REE fractionation in the host phonolite via earlier-crystallized garnets. Such examples for extreme changes in HREE in garnets are only known for hydrothermal grandites by REE-bearing fluids. The second garnet population is homogeneous and formed in a closed system. Near-flat patterns between Sm and Lu confirm experimental data indicating lower D(Sm)/ D(Lu) for Ca-rich garnets than for e.g. pyrope-rich garnets. It follows: D Grt/PhMelt for La = 0.5, Sm = 48 and Yb = 110.

Scheibner, Birgit; Wörner, Gerhard; Civetta, Lucia; Stosch, Heinz-Günter; Simon, Klaus; Kronz, Andreas

2007-07-01

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

Evaluation of plant availability of rare earth elements in soils by chemical fractionation and multiple regression analysis  

Microsoft Academic Search

This case field study describes the distribution of rare earth elements (REEs) in different soil fractions obtained by a sequential extraction procedure and plant availability with single correlation and multiple regression analysis. Soil and plant samples were collected from a rural region of Beijing, China. Plant samples (corn, rice) were segmented into grain, stem, leaf and root. The results indicated

Fuliang Li; Xiaoquan Shan; Tianhong Zhang; Shuzhen Zhang

1998-01-01

4

Rare Earth Element Concentrations, Speciation, and Fractionation along Groundwater Flow Paths: The Carrizo Sand (Texas) and Upper Floridan Aquifers  

Microsoft Academic Search

Groundwater samples were collected in two different types of aquifers (i.e., Carrizo sand aquifer, Texas and Upper Floridan\\u000a carbonate aquifer, west-central Florida) to study the concentration, speciation, and fractionation of rare earth elements\\u000a (REE) along the groundwater flow path in each system. Major solutes and dissolved organic carbon (DOC) were also measured\\u000a in these groundwaters. In the Carrizo aquifer, groundwaters

Jianwu Tang; Karen H. Johannesson

5

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

6

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 3 and HF\\/HNO 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

Edward R. Sholkovitz; William M. Landing; Brent L. Lewis

1994-01-01

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

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

SciTech Connect

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

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

1983-01-01

9

Mobility and fractionation of rare earth elements in argillaceous sediments: Implications for dating diagenesis and low-grade metamorphism  

NASA Astrophysics Data System (ADS)

We report Sm-Nd and Rb-Sr data for the fine fractions of Lower Paleozoic argillaceous rocks from Wales, UK and New York, USA, spanning the range of low-grade metamorphic conditions from the diagenetic zone (zeolite facies) to the epizone (greenschist facies). In all cases, leaching of the fine fractions results in a high 147Sm /144Nd (0.09-0.29) acid-soluble component and a complementary low 147Sm /144Nd (0.05-0.14) residual component. The observed fractionation is an ancient feature related to diagenesis, burial and metamorphism. The magnitude of Sm-Nd fractionation between leachates and residues, as well as the resulting Sm-Nd ages, vary as a function of grain size and metamorphic grade. Uncleaved Welsh mudrocks of the diagenetic zone yield Sm-Nd leachate-residue ages of 453-484 Ma, in agreement with their Llanviian to Caradocian biostratigraphic ages, whereas higher grade rocks of the anchizone and epizone yield Sm-Nd ages as young as 413 Ma. These ages are transitional between the time of deposition and the time of regional deformation related to the Acadian Orogeny at 390 Ma. Distinct convex-upward rare earth element (REE) patterns of the leachates suggest that the precipitation of early diagenetic apatite controls the trace element budget of the rock, forcing a depletion of middle REEs on the subsequently formed diagenetic phyllosilicates. The amount of organic matter present and the extent of later prograde reactions are probable modifiers of this fractionation process. Ordovician and Devonian clastic rocks associated with the Trenton and Onondaga limestones of New York yield single-sample and multi-sample Sm-Nd isochron ages that agree well with their biostratigraphic ages of 454 Ma and 390 Ma, respectively. The REE fractionation observed in shale leachates of the Ordovician Utica Formation is related to Ca/Mg of the bulk rock and hence to the composition of the diagenetic carbonate cement. In all cases the Sm-Nd system remained closed subsequent to the peak of diagenesis or metamorphism, including the North American rocks that show no evidence of being isotopically reset during widespread remagnetization of the subjacent limestone units in the late Paleozoic.

Ohr, Matthias; Halliday, Alexander N.; Peacor, Donald R.

1994-01-01

10

High field strength element/rare earth element fractionation during partial melting in the presence of garnet: Implications for identification of mantle heterogeneities  

NASA Astrophysics Data System (ADS)

A synthesis of recent garnet-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 and eclogitic source rocks. Garnet-melt partition coefficients DGrt/Melt are very sensitive to changes in garnet major element composition. Specifically, high-pressure, high-temperature experimental studies show that high field strength elements (HFSE) Zr, Hf, and Ti are incompatible in garnets with <19 ± 1 mol% Ca on their X site, with DTi < DZr ? DHf < 1, while at higher Ca levels, all three become compatible with DZr > DHf > DTi > 1. U and Th also have higher partition coefficients at higher garnet Ca contents, while the amount of fractionation between the two decreases. In contrast, the heavy rare earth element partition coefficients DHREE are hardly affected by a change in garnet Ca content. We provide a semiquantitative explanation for the behavior of the high field strength elements based on a crystal lattice strain model in which Zr and Hf are split between the X and Y sites in Ca-rich garnet and in which significant changes in garnet elasticity occur as a function of garnet composition. The large variations in both absolute DGrt/Melt values and DGrt/Melt ratios (e.g., DZr/DYb), in conjunction with compositional differences between natural peridotitic (Ca poor) and eclogitic (Ca richer) garnets, allow identification of trace element ratios that may best serve as a fingerprint for the presence of eclogitic garnet. We present simple batch melting calculations for two end-member melting scenarios (anhydrous garnet peridotite melting and anhydrous bimineralic eclogite melting). Our calculations show that near-uniform Zr/HREE and Hf/HREE as a function of melt fraction, in combination with Hf/Sm and Zr/Sm ratios that are smaller than the source ratio, could serve as fingerprints for the presence of Ca-rich garnet in the source of mantle melts. Our calculations show that it is impossible to define one unique "garnet signature" to determine the presence or absence of garnet in basalt sources but rather that different garnet-bearing sources are likely to produce distinctly different "garnet signatures."

van Westrenen, Wim; Blundy, Jonathan D.; Wood, Bernard J.

2001-07-01

11

Mobility and fractionation of rare earth elements during supergene weathering and gossan formation and chemical modification of massive sulfide gossan  

NASA Astrophysics Data System (ADS)

Primary massive sulfide gossans (MSG) in the Bathurst Mining Camp (BMC), New Brunswick, Canada, are characterized by relative enrichment of Au, Sb, and As, formation of jarosite group minerals (jarosite, plumbojarosite, and argentojarosite) and little or no fractionation in the rare earth elements (REE), including preservation of large positive Eu anomalies (average [Eu/Eu*]NASC = 4.14 in MSG; 6.61 in massive sulfide mineralization; 0.60 in host rocks). The chemical and mineralogical characteristics of MSG (e.g., Halfmile Lake deposit) imply low pH (<3) and relatively oxidizing conditions during gossan formation; oxidation of a volcanogenic massive sulfide body (comprising pyrite, pyrrhotite, sphalerite, galena, and chalcopyrite) with a falling water table. The lack of light REE or heavy REE fractionation and preservation of positive Eu anomalies characteristic of the original (465 Ma) hydrothermal fluid is consistent with relatively large water rock ratios during massive sulfide mineralization oxidation, and removal of the REE predominantly as sulfate complexes (LnSO4+, Ln(SO4)2-). Low pH groundwaters recovered from past producing mines in the BMC display REE patterns reflecting those inferred to have occurred during gossan formation. Gossan at the Restigouche deposit, in contrast to the Halfmile Lake deposit, displays mineralogical and chemical evidence for having been chemically reworked since primary gossan formation. Evidence for chemical reworking includes loss of primary massive sulfide mineralization textures, replacement of plumbojarosite with anglesite, almost complete removal of jarosite minerals, loss of Au, Sb, and As and apparent preferential removal of Eu, resulting in loss of positive Eu anomalies for most samples (average [Eu/Eu*]NASC = 1.21 in the gossan, with many displaying strong negative anomalies; 3.65 in massive sulfide mineralization; 0.54 in host rocks). Based on geochemical modeling, conditions inferred for the chemical reworking of the Restigouche deposit include near neutral conditions and either relatively oxidizing conditions with Eu2+ hosted in a preferentially weathered mineral host (possibly through substitution for Pb in plumbojarosite and beudantite) or cycling between reduced and oxidized conditions during gossan reworking.

Leybourne, Matthew I.; Peter, Jan M.; Layton-Matthews, Daniel; Volesky, John; Boyle, Dan R.

2006-03-01

12

Mobility and fractionation of rare earth elements in argillaceous sediments: Implications for dating diagenesis and low-grade metamorphism  

Microsoft Academic Search

We report Sm-Nd and Rb-Sr data for the fine fractions of Lower Paleozoic argillaceous rocks from Wales, UK and New York, USA, spanning the range of low-grade metamorphic conditions from the diagenetic zone (zeolite facies) to the epizone (greenschist facies). In all cases, leaching of the fine fractions results in a high 147 Sm \\/ 144 Nd (0.09-0.29) acid-soluble component

Matthias Ohr; Alexander N. Halliday; Donald R. Peacor

1994-01-01

13

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

14

Fractionation of rare earth elements in refractory inclusions from the Ningqiang meteorite: Origin of positive anomalies in Ce, Eu, and Yb  

NASA Astrophysics Data System (ADS)

Ion microprobe analyses of rare earth elements (REEs), Ba, and Hf were performed for various types of refractory inclusions including amoeboid olivine aggregates (AOAs) from the Ningqiang ungrouped carbonaceous chondrite to search for possible relationships between REE abundance patterns and bulk chemical compositions of the inclusions. Four types of CI-normalized REE patterns were recognized: (1) nearly flat (unfractionated) pattern with or without Eu (and Yb) anomalies (Groups I, III, or V), (2) depletions of ultrarefractory heavy REEs (HREEs) relative to light REEs (LREEs), and depletions of Eu and Yb ( Group II, but without depletion of Yb in some cases), (3) depletions of ultrarefractory HREEs with positive anomalies in Ce, (Eu), and Yb ( Modified Group II), and (4) nearly flat pattern with positive anomalies in Ce, (Eu), and Yb ( Modified Group I). No systematic correlation was found between bulk chemical compositions and REE patterns of the inclusions. This suggests that the observed REE fractionations occurred prior to condensation of major elements (e.g., Mg and Si) which defined bulk chemical compositions of the inclusions. It is remarkable that 7 out of 19 inclusions show positive anomalies in Ce, Yb, and in some cases, Eu as well (Modified Group I and Modified Group II), suggesting that such anomalies are rather common among inclusions in the Ningqiang and possibly in other primitive meteorites. Two possible mechanisms are considered for the formation of Modified Group II and Modified Group I patterns. In Model 1, Modified Group II is formed by a process similar to that produced Group II but removal of ultrarefractory dust occurred at slightly lower temperatures, where not only ultrarefractory HREEs but some fraction of LREEs had been condensed and removed from the system. Modified Group I may be explained by addition of an unfractionated component to the Modified Group II component, or alternatively, by partial removal of ultrarefractory dust from the system. In Model 2, Modified Group II is formed by later addition of Ce, (Eu), and Yb onto fine-grained dust or inclusions having HREE-depleted, Group II-like REE patterns. Similarly, Modified Group I is explained by later addition of Ce, (Eu), and Yb onto those with almost unfractionated REE patterns. The observed REE data show that both the degree of HREE-depletion (e.g., Er-depletion) and that of fractionation among HREEs (e.g., depletion in the Er/Gd ratio) for Modified Group II are very similar to those for Group II. Model 1 predicts almost complete removal of ultrarefractory HREEs from the system, resulting in much higher HREE-depletion for Modified Group II, which is not consistent with the present observations. Addition of an unfractionated component may explain moderate depletion of HREEs in Modified Group II, but it will diminish fractionation among HREEs, which is not consistent with the present observations. In contrast, Model 2 predicts no correlations between Ce-(Eu)-Yb-enrichment and HREE-depletion or between Ce-(Eu)-Yb-enrichment and fractionation among HREEs, consistent with the present observations. Hence, Model 2 seems more likely. If this is the case, at least two distinct regions with different REE characteristics are required for the formation of Modified Group II inclusions: one is a high temperature region where Group II-like (HREE-depleted) inclusions or their precursors are formed by condensation from a fractionated gas after removal of ultrarefractory dust, and another is a low temperature region enriched in Ce, Eu, and Yb in the gas phase. Abundant occurrence of positive Ce-(Eu)-Yb anomalies suggests that migration of solid materials from one region to another occurs rather frequently in the solar nebula. The most likely place satisfying such conditions for the formation of these inclusions may be the innermost part of the protoplanetary disk.

Hiyagon, H.; Yamakawa, A.; Ushikubo, T.; Lin, Y.; Kimura, M.

2011-06-01

15

Mechanical Analogies of Fractional Elements  

NASA Astrophysics Data System (ADS)

A Ffactional element model describes a special kind of viscoelastic material. Its stress is proportional to the fractional-order derivative of strain. Physically the mechanical analogies of fractional elements can be represented by spring-dashpot fractal networks. We introduce a constitutive operator in the constitutive equations of viscoelastic materials. To derive constitutive operators for spring-dashpot fractal networks, we use Heaviside operational calculus, which provides explicit answers not otherwise obtainable simply. Then the series-parallel formulas for the constitutive operator are derived. Using these formulas, a constitutive equation of fractional element with 1/2-order derivative is obtained. Finally we find the way to derive the constitutive equations with other fractional-order derivatives and their mechanical analogies.

Hu, Kai-Xin; Zhu, Ke-Qin

2009-10-01

16

Rare earth element fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA  

Microsoft Academic Search

Rare earth element (REE) concentrations were measured in 5 well water samples and 3 springs located along a groundwater flow path in a shallow, tuffaceous alluvial aquifer from southern Nevada, USA. The REE concentrations in these groundwaters decrease in the direction of groundwater flow. A previous investigation demonstrated that REE solid-liquid phase partitioning coefficients (i.e., Kd’s) for groundwaters from tuffaceous

Kevin H. Johannesson; Irene M. Farnham; Caixia Guo; Klaus J. Stetzenbach

1999-01-01

17

Rare earth elements (REE) and yttrium in stream waters, stream sediments, and Fe Mn oxyhydroxides: Fractionation, speciation, and controls over REE + Y patterns in the surface environment  

NASA Astrophysics Data System (ADS)

We have collected ˜500 stream waters and associated bed-load sediments over an ˜400 km 2 region of Eastern Canada and analyzed these samples for Fe, Mn, and the rare earth elements (REE + Y). In addition to analyzing the stream sediments by total digestion (multi-acid dissolution with metaborate fusion), we also leached the sediments with 0.25 M hydroxylamine hydrochloride (in 0.05 M HCl), to determine the REE + Y associated with amorphous Fe- and Mn-oxyhydroxide phases. We are thus able to partition the REE into "dissolved" (<0.45 ?m), labile (hydroxylamine) and detrital sediment fractions to investigate REE fractionation, and in particular, with respect to the development of Ce and Eu anomalies in oxygenated surface environments. Surface waters are typically LREE depleted ([La/Sm] NASC ranges from 0.16 to 5.84, average = 0.604, n = 410; where the REE are normalized to the North America Shale Composite), have strongly negative Ce anomalies ([Ce/Ce ?] NASC ranges from 0.02 to 1.25, average = 0.277, n = 354), and commonly have positive Eu anomalies ([Eu/Eu ?] NASC ranges from 0.295 to 1.77, average = 0.764, n = 84). In contrast, the total sediment have flatter REE + Y patterns relative to NASC ([La/Sm] NASC ranges from 0.352 to 1.12, average = 0.778, n = 451) and are slightly middle REE enriched ([Gd/Yb] NASC ranges from 0.55 to 3.75, average = 1.42). Most total sediments have negative Ce and Eu anomalies ([Ce/Ce ?] NASC ranges from 0.097 to 2.12, average = 0.799 and [Eu/Eu ?] NASC ranges from 0.39 to 1.43, average = 0.802). The partial extraction sediments are commonly less LREE depleted than the total sediments ([La/Sm] NASC ranges from 0.24 to 3.31, average = 0.901, n = 4537), more MREE enriched ([Gd/Yb] NASC ranges from 0.765 to 6.28, average = 1.97) and Ce and Eu anomalies (negative and positive) are more pronounced. The partial extraction recovered, on average ˜20% of the Fe in the total sediment, ˜80% of the Mn, and 21-29% of the REEs (Ce = 19% and Y = 32%). Comparison between REEs in water, partial extraction and total sediment analyses indicates that REEs + Y in the stream sediments have two primary sources, the host lithologies (i.e., mechanical dispersion) and hydromorphically transported (the labile fraction). Furthermore, Eu appears to be more mobile than the other REE, whereas Ce is preferentially removed from solution and accumulates in the stream sediments in a less labile form than the other REEs + Y. Despite poor statistical correlations between the REEs + Y and Mn in either the total sediment or partial extractions, based on apparent distribution coefficients and the pH of the stream waters, we suggest that either sediment organic matter and/or possibly ?-MnO 2/FeOOH are likely the predominant sinks for Ce, and to a lesser extent the other REE, in the stream sediments.

Leybourne, Matthew I.; Johannesson, Karen H.

2008-12-01

18

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

19

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

Microsoft Academic Search

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

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

2001-01-01

20

Magnetite fractionation of "chalcophile" elements  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

21

Rare earth elements in the Amazon basin  

NASA Astrophysics Data System (ADS)

The rare earth element (REE) concentrations of the dissolved and particulate fractions and bed sediment between Manaus and Santarém in the Amazon River, and in some major tributaries, were evaluated. A very important zone in the Amazon basin, the encontro das aguas area where the Rio Solimões and the Rio Negro meet, was especially sampled. Different size fractions were isolated by ultrafiltration. Water samples were collected at different stages of the mixing. Three groups of waters are distinguished: group I has a low pH (<5·5) and is represented by the Negro basin rivers; group II has alkalinity less than 0·2 meq l-1 and is represented by the Rios Tapajós and Trombetas; group III has high alkalinity (>0·2 meq l-1) and higher pH (>6·5) and is represented by the Madeira basin rivers, the Solimões and the Amazon. The highest dissolved REE concentration is in the Rio Negro and the lowest in the Rio Tapajós (dissolved REEs vary by more than a factor of ten). The solubility of REEs is pH dependent: in river waters with a pH < 6 the Ce concentration is twice that of La, whereas in rivers with a higher pH the concentrations of Ce and La are similar. Dissolved REE concentrations are positively correlated with the dissolved organic carbon. Correlations between Fe, Al, and La suggest that La is associated with Al (Fe)-rich organic matter and/or related to dissolved Fe-rich inorganic material. Dissolved REEs normalized to North American shale composite show an enrichment in intermediate/heavy REEs (from Eu to Er), except for the shields rivers (such as Rio Negro and Rio Trombetas). Both of them are depleted in heavy REEs and show a relative Ce enrichment. In contrast, for the Andeans rivers (such as Rio Solimões), light REEs are slightly depleted and a negative Ce relative anomaly occurs. The pattern of the Amazon River at Óbidos confirms the major influence of the Rios Negro and Solimões with REE fractionation. For the Rio Negro, 60 to 70% of REEs are concentrated in the particulate fraction (>0·2 µm), 20 to 30% are in the colloidal fraction (0·2 µm to 5000 Da) and less than 10% are in solution (<5000 Da). For the Solimões the distribution is different. More than 95% of REEs are in the particulate fraction. In the mixing area, the colloidal fraction is enriched in heavy REEs.

Gerard, M.; Seyler, P.; Benedetti, M. F.; Alves, V. P.; Boaventura, G. R.; Sondag, F.

2003-05-01

22

The rare earth elements in seawater  

Microsoft Academic Search

The depth distributions of La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb in the oceanic water column are used to evaluate the marine geochemical cycle of the rare earth elements and their application as water-mass tracers.

Henry Elderfield; Mervyn J. Greaves

1982-01-01

23

Chemical and isotopic fractionation during the evaporation of the FeO-MgO-SiO 2-CaO-Al 2O 3-TiO 2 rare earth element melt system  

Microsoft Academic Search

A synthetic material with solar elemental proportions of iron, magnesium, silicon, titanium, calcium, and aluminum oxides and doped with rare earth elements was evaporated in a vacuum furnace at 1800 and 2000°C for different durations to study its chemical and isotopic evolution during the evaporation process. It is demonstrated that kinetic evaporation of solar composition material can produce residues of

Jianhua Wang; Andrew M Davis; Robert N Clayton; Toshiko K Mayeda; Akihiko Hashimoto

2001-01-01

24

Rare earth element investigation of the Cliefden Outcrop, N.S.W., Australia  

Microsoft Academic Search

The effect of low grade hydrous burial metamorphism (prehnite-pumpellyite facies) upon the rare earth elements (REE) has been studied by using samples from the Cliefden Outcrop, New South Wales. The REE, together with other reputedly `immobile' elements, have been mobilised during the metamorphism. Although mobile, the REE have behaved remarkably coherently with little light rare earth (LREE) fractionation. This is

Phillip L. Hellman; Raymond E. Smith; Paul Henderson

1977-01-01

25

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

26

Rare earth element investigation of the Cliefden Outcrop, N.S.W., Australia  

Microsoft Academic Search

The effect of low grade hydrous burial metamorphism (prehnite-pumpellyite facies) upon the rare earth elements (REE) has been studied by using samples from the Cliefden Outcrop, New South Wales. The REE, together with other reputedly ‘immobile’ elements, have been mobilised during the metamorphism. Although mobile, the REE have behaved remarkably coherently with little light rare earth (LREE) fractionation. This is

Phillip L. Hellman; Raymond E. Smith; Paul Henderson

1977-01-01

27

Ion probe measurement of rare earth elements in biogenic phosphates  

SciTech Connect

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

Grandjean, P.; Albarede, F. (Ecole Nationale Superieure de Geologie (France))

1989-12-01

28

Rare earth element systematics in hydrothermal fluids  

NASA Astrophysics Data System (ADS)

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°C) percolating through different rock types may show similar REE patterns.

Michard, Annie

1989-03-01

29

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

30

Rare earth elements in alpine peridotites  

Microsoft Academic Search

The samples from alpine peridotite massifs (Beni Bouchera, Lherz and the Alps) have been analyzed for rare earth elements. The peridotites as a whole are characterized by various degrees of light REE depletion (Ce varies from 1.2 to 0.02 times chondrite) and a small variation in heavy REE (Yb varies about a factor of 2, from 1.3 to 2.2 times

M. Loubet; N. Shimizu; C. J. Allègre

1975-01-01

31

Rare earth element systematics in hydrothermal fluids  

Microsoft Academic Search

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°C) percolating

Annie Michard

1989-01-01

32

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

33

Preparation of microcapsules containing rare-earth metal elements.  

PubMed

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

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

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

Geochemistry of Suspended Particulate Matter (SPM) in the Murray-Darling River System: A Conceptual Isotopic\\/Geochemical Model for the Fractionation of Major, Trace and Rare Earth Elements  

Microsoft Academic Search

A conceptual isotopic\\/geochemical model is presented to explain the variation of major, trace and rare earth element (REE)\\u000a geochemistry and Sr isotope systematics in suspended particulate matter (SPM) as a function of particle\\/colloid size. This\\u000a conceptual model is an extension of a previous investigation of the origin of SPM in the Murray-Darling River system (MDRS)\\u000a that utilised Sr isotope systematics

G. B. Douglas; B. T. Hart; R. Beckett; C. M. Gray; R. L. Oliver

1999-01-01

37

Anthropogenic Cycles of Rare Earth Elements  

NASA Astrophysics Data System (ADS)

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

Du, X.; Graedel, T. E.

2009-12-01

38

Tipping elements in the Earth's climate system  

SciTech Connect

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

Lenton, T.M. [Univ. of East Anglia and Tyndall Centre for Climate Change Research, Norwich (GB). School of Environmental Sciences; Held, H.; Lucht, W.; Rahmstorf, S. [Potsdam Inst. for Climate Impact Research (Germany); Kriegler, E. [Potsdam Inst. for Climate Impact Research (Germany)]|[Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Engineering and Public Policy; Hall, J.W. [Newcastle Univ. and Tyndall Centre for Climate Change Research (GB). School of Civil Engineering and Geosciences; Schellnhuber, H.J. [Potsdam Inst. for Climate Impact Research (Germany)]|[Oxford Univ. and Tyndall Centre for Climate Change Research (GB). Environmental Change Inst.

2008-02-12

39

Alloying Characteristics of the Rare Earth Elements with the Transition Elements.  

National Technical Information Service (NTIS)

The alloying characteristics of the rare earth elements with the transition metals undergo a radical change as the atomic number of the transition series increases - - transition elements in Groups IVa, Va, and VIa are immiscible with the rare earths, whi...

R. P. Elliott

1964-01-01

40

Quantitative modeling of trace element fractionation during incongruent dynamic melting  

NASA Astrophysics Data System (ADS)

A recent significant achievement in trace element modeling is the development of the congruent (eutectic) dynamic melting (CDM) model where only melt is generated. However, melting reactions in the mantle and crust often produce not only melt but also minerals. By introducing melting reactions into the dynamic melting model, we present a series of equations for incongruent dynamic melting (IDM). We also compare IDM with incongruent batch melting (IBM) and CDM. The difference in calculation results between IDM and IBM is significant, particularly for incompatible elements in the residual melt and the total residue. The difference between IDM and CDM is noticeable when the fraction of the product minerals is significant and when the distribution coefficient of the product mineral is sufficiently different from those of the reaction minerals. More realistic but more complex IDM models are also derived to further account for the progressive changes in partition coefficients, the variations in the net fractional contribution of a phase to the total melt, and the consumption of a solid phase. Applications of IDM equations to model residual clinopyroxenes are illustrated. Distinctive rare earth element (REE) patterns with a middle REE hump in clinopyroxene can be produced by partial melting in garnet stability field. The IDM equations presented here are very useful in modeling partial melting of both the mantle and the crust.

Zou, Haibo; Reid, Mary R.

2001-01-01

41

Are C1 chondrites chemically fractionated - A trace element study  

Microsoft Academic Search

Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for a large variety of elements, including rare earths. The sample processing is described, including the irradiation, chemical procedure, rare earths separation, counting techniques, radiochemical purity check, and chemical yields. The results of consistency checks on a number of elements are

Mitsuru Ebihara; Rainer Wolf; Edward Anders

1982-01-01

42

Rare earth element analysis indicates micropollutants in an urban estuary  

NASA Astrophysics Data System (ADS)

Rare earth element analysis of Bayou Bienvenue waters shows anomalously high gadolinium, Gd, concentrations relative to its nearest neighbors in the REE series, europium and terbium. The anomalously high Gd concentrations indicate anthropogenic input from waste-water treatment plants in the area as anthropogenic Gd input can be traced back to its use as a contrast agent in magnetic resonance imaging in hospitals. Others have shown that anomalously high levels of Gd in natural waters are likely to be associated with other micropollutants that also occur in hospital effluent and that are not removed in the wastewater treatment process, including pharmaceuticals in the form of steroids, antihistamines, and antibiotics. Estuaries serve as many important ecological roles and have been shown to act as a filter for pollutants. To better understand the transport, biogeochemical cycling, and ultimate fate of trace elements in estuaries, I collected surface water samples from Bayou Bienvenue, a wetland triangle that covers an area of 427 acres directly adjacent to New Orleans, Louisiana. Water samples from Bayou Bienvenue were collected along the salinity gradient and subsequently filtered through progressively smaller pore-size filters. The resulting fractions were analyzed for trace element concentions, including the REEs, by magnetic sector ICP-MS. The attached figure shows the Gd anomaly present in the particulate (>0.45?m) fraction. Upper continental crust (UCC)-normalized plots of colloidal REEs (0.02?m - 0.45?m) fraction is lacking this anomaly indicating anthropogenic Gd is found chiefly in the particulate fraction in Bayou Bienvenue. No clear relationship between Gd concentration and salinity was apparent.

Mohajerin, T. J.; Johannesson, K. H.; Kolker, A.; Burdige, D. J.; Chevis, D.

2011-12-01

43

SEPARATION OF RARE EARTH ELEMENTS BY FOCUSSING CHROMATOGRAPHY  

Microsoft Academic Search

Focusing chromatography was applied to the mutual separation of rare ; earth elements and the effect of several conditions upon the separation of rare ; earth elements was studied. The most satisfactory result was obtained when: 0.1M ; citric acid was used as the complexing agent and 0.01N hydrochloric acid as the ; decomplexing agent, pH gradient of both solutions

Y. Kamemoto; K. Hagiya; S. Yamagishi

1963-01-01

44

Concentration of rare earth elements in five ordinary chondrites  

Microsoft Academic Search

The concentration of rare-earth elements in the chondrites Saratov, ; Elenovka, Pervomaiskii Poselok (L group), Zaisan, and Zhovtnevyi Khutor (H group) ; was determined by neutron activation. It was established that (1) in meteorites ; of the L group in comparison with the chondrites of the H group the light rare-; earth elements (from La to Eu) slightly predominate; (2)

Kolesov

1974-01-01

45

Rare earth elements in natural calcite  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) have been used for years as a tool for interpreting rock genesis but recently they have come to be used as good analogues for the tri--valent actinides. Although there are abundant data in the literature describing their relative proportions in rocks, data for individual minerals and factors controlling their uptake are lacking. Better understanding of the extent of REE incorporation in all minerals would provide valuable information about the extent of immobilisation one could expect in the event of escape of radioactive elements. When concrete waste repositories break down, calcite forms in the high pH, Ca-rich solutions. Calcium's electronic structure permits significant distortion in its octahedral coordination, so divalent ions substitute extensively when size is compatible. The trivalent REE's, whose radii are similar to calcium, substitute to some extent but the range of possible uptake is unknown. This study was designed to fill that gap. With help from museums and mineral collectors internationally, we have collected a suite of calcite samples from well--characterised genetic environments. These include limestone, dolomite, marble, pegmatite, hydrothermal vein fillings, regionally metamorphosed settings and skarn, as well as several types of calcitic fossils. We used inductively coupled plasma-mass spectroscopy (ICP--MS) with isotope dilution to analyse the REE content. Data show expected trends. The most interesting result so far is that the highest natural REE concentrations are significantly lower than expected from the distribution coefficients we determined experimentally, suggesting calcite takes up essentially all REE's available from solution. This is good news for natural attenuation in the vicinity of decomposing concrete repositories because one could expect immobilisation of the actinides whose behaviour is similar to that of the lanthanides. The negative side is that recrystallisation or dissolution could release them again.

Jensen, J. T.; Harstad, A. O.; Waight, T. E.; Stipp, S. L. S.

2003-04-01

46

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

47

Chemical fractionation in the silicate vapor atmosphere of the Earth  

NASA Astrophysics Data System (ADS)

Despite its importance to questions of lunar origin, the chemical composition of the Moon is not precisely known. In recent years, however, the isotopic composition of lunar samples has been determined to high precision and found to be indistinguishable from the terrestrial mantle despite widespread isotopic heterogeneity in the Solar System. In the context of the giant-impact hypothesis, this level of isotopic homogeneity can evolve if the proto-lunar disk and post-impact Earth undergo turbulent mixing into a single uniform reservoir while the system is extensively molten and partially vaporized. In the absence of liquid-vapor separation, such a model leads to the lunar inheritance of the chemical composition of the terrestrial magma ocean. Hence, the turbulent mixing model raises the question of how chemical differences arose between the silicate Earth and Moon. Here we explore the consequences of liquid-vapor separation in one of the settings relevant to the lunar composition: the silicate vapor atmosphere of the post-giant-impact Earth. We use a model atmosphere to quantify the extent to which rainout can generate chemical differences by enriching the upper atmosphere in the vapor, and show that plausible parameters can generate the postulated enhancement in the FeO/MgO ratio of the silicate Moon relative to the Earth's mantle. Moreover, we show that liquid-vapor separation also generates measurable mass-dependent isotopic offsets between the silicate Earth and Moon and that precise silicon isotope measurements can be used to constrain the degree of chemical fractionation during this earliest period of lunar history. An approach of this kind has the potential to resolve long-standing questions on the lunar chemical composition.

Pahlevan, Kaveh; Stevenson, David J.; Eiler, John M.

2011-01-01

48

Rare earth elements as indicators of different marine depositional environments in chert and shale  

Microsoft Academic Search

Differences in rare earth element (REE) relative fractionations and total abundances in marine cherts and shales reflect the depositional location of the sediments. Based on cerium anomaly (Ce\\/Ce*) and total REE abundance (ΣREE) variations preserved in interbedded chert and shale sequences of the Franciscan assemblage, the Claremont Formation, and the Monterey Formation of coastal California, we can resolve three depositional

Richard W. Murray; D. L. Jones; M. R. Bruchholtz ten Brink; David C. Gerlach; G. Price Russ III

1990-01-01

49

Rare earth elements as provenance indicators in North Australian estuarine and coastal marine sediments  

Microsoft Academic Search

Rare earth elements (REE) in three grain size fractions of clay-dominated estuarine and coastal sediments from the North Australian coastline have been investigated for use as potential provenance indicators. Comparisons of data based on instrumental neutron activation analysis and inductively coupled plasma mass spectrometry revealed that HF digestions of zircon-bearing samples resulted in unsatisfactory recovery of REE. Instead, a relatively

Niels Crosley Munksgaard; Kezia Lim; David Livingstone Parry

2003-01-01

50

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

51

The aquatic chemistry of rare earth elements in rivers and estuaries  

Microsoft Academic Search

Laboratory experiments were carried out to determine how pH, colloids and salinity control the fractionation of rare earth elements (REEs) in river and estuarine waters. By using natural waters as the reaction media (river water from the Connecticut, Hudson and Mississippi Rivers) geochemical reactions can be studied in isolation from the large temporal and spatial variability inherent in river and

Edward R. Sholkovitz

1995-01-01

52

Fractional Electrical Impedances in Botanical Elements  

Microsoft Academic Search

Fractional calculus (FC) is no longer considered solely from a mathematical viewpoint, and is now applied in many emerging scientific areas, such as electricity, magnetism, mechanics, fluid dynamics, and medicine. In the field of dynamical systems, significant work has been carried out proving the importance of fractional order mathematical models. This article studies the electrical impedance of vegetables and fruits

ISABEL S. JESUS; J. A. Tenreiro Machado; J. Boaventure Cunha

2008-01-01

53

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

54

Rare earth elements in soil and plant systems - A review  

Microsoft Academic Search

The rare earth elements (REEs) form a chemically uniform group and include yttrium (Y), lanthanum (La) and the lanthanides\\u000a cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb),\\u000a dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Their average abundance in the\\u000a Earth’s crust range from 66µg g?1 in

Germund Tyler

2004-01-01

55

Trace Rare Earth Element Analysis in Briny Groundwaters.  

National Technical Information Service (NTIS)

A rare-earth element (REE) group separation scheme has been developed. REE data for two briny groundwaters representing Granite Wash and Wolfcamp Carbonate formations are reported. (ERA citation 12:038045)

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

1986-01-01

56

Element and isotope fractionation in preplanetary nebula  

NASA Astrophysics Data System (ADS)

Theoretical work on chemical and isotopic fractionation in the solar system is reviewed. A possible evolutionary stage of the presolar cloud is that of a turbulent accretion disk which is continuously fed from a surrounding envelope, contains dust and gas, is hot in the center (a few 1000 K) and the temperature decreases with distance from the rotation axis. Dust particles initially contain an admixture of chemical components, from volatile ices to refractory oxides. Transport within the disk leads to a systematic spatial chemical fractionation by selective sublimation and condensation of the various components in different regions. Physico-chemical processes, which in general are mass-dependent, lead to a spatial isotope fractionation. It is possible that these macroscopic structures imprinted on the presolar cloud may be preserved in solid solar system matter today. The consequences of the theory are compared with measurements in the solar system.

Morfill, G. E.

57

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

58

The Oceanic Chemistry of the Rare-Earth Elements  

Microsoft Academic Search

Because of the unique chemical characteristics of the rare-earth elements (REES), they provide information as oceanic tracers of element source and reactivity. The absolute and relative concentrations of the REES in ocean waters reflect their input from rivers, by aeolian transport and from hydrothermal vents; their interaction with the bio-geochemical cycle involving removal from surface waters by adsorption and oxidation

H. Elderfield; M. Whitfield; J. D. Burton; M. P. Bacon; P. S. Liss

1988-01-01

59

Origins and early evolution of volatile elements in Earth  

Microsoft Academic Search

The origin and evolution of volatile elements is a long standing problem not yet fully resolved. Stable isotope (H and N) systematics of the Sun (now documented for N thanks to the Genesis mission [1]), meteorites, giant planets and comets indicate that volatile elements of Earth (and Mars) share isotopic similarities with chondritic volatiles and therefore were supplied by chondritic

B. Marty

2009-01-01

60

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

National Technical Information Service (NTIS)

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

C. Hurst

2010-01-01

61

Trace Element Fractionation in Kamacite and Taenite in IVA Irons  

NASA Astrophysics Data System (ADS)

We have used laser ablation ICP-MS to measure trace element concentrations in kamacite and taenite. These analyses show that there is limited potential for fractionation between these phases and it is largely controlled by diffusion.

Ash, R. D.; Luong, M. V.; Walker, R. J.; McDonough, W. F.; McCoy, T. J.

2007-03-01

62

Fractionated space infrastructure for long-term earth observation missions  

NASA Astrophysics Data System (ADS)

A fractionated spacecraft is a space system that distributes its functionalities, such as computation, communication, data storage, payload and even power generation, over several independent satellite modules that share those functionalities through a wireless link. This paper exploits this innovational architecture to design a space infrastructure that is able to accept and support multiple Earth Observation (EO) payload modules. In this paper the functional, physical and organizational architectures of the infrastructure are presented. To start with, EO programs utilizing monolithic spacecraft especially SPOT and Landsat programs are reviewed and analyzed to derive the inherent EO functional requirements. Then these functional requirements are integrated into an EO scenario based on a reference orbit typically for EO missions. Next, novel architectures of fractionated spacecraft are reviewed and the inherent non traditional attributes are summarized and classified in such a way to show their close interrelation with the EO functional requirements. Then four resources components: high bandwidth downlink component, data relay satellite communication component, mission data processor component and large volume data storage component are identified and designated to establish the EO space infrastructure. Based on those four components different physical architectures are designed for the specific scenario and then are evaluated using the Analytical Hierarchy Process (AHP) with eight selection criteria. Afterwards, the best option has been identified, which comprises four heterogeneous modules assigned to host those four resources components separately. Finally, this physical architecture is organized by means of the Multi-Agent System (MAS) theory, which fulfills best the EO non traditional requirements. The proposed organization is tailored for the autonomous operations of the fractionated infrastructure and is based on the peer-to-peer architecture. From a physica- and organizational perspective, the developed space infrastructure is able to self-adapt, self-optimize and self-configure to dynamic changes in various local environmental conditions.

Chu, Jing; Guo, Jian; Gill, E. K. A.

63

Cumulative damage fraction design approach for LMFBR metallic fuel elements  

Microsoft Academic Search

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

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

1979-01-01

64

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

SciTech Connect

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

Jenkins, G.S.

1995-06-15

65

Attenuation of rare earth elements in a boreal estuary  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

66

Colors of a Second Earth: Estimating the Fractional Areas of Ocean, Land, and Vegetation of Earth-like Exoplanets  

Microsoft Academic Search

Characterizing the surfaces of rocky exoplanets via their scattered light will be an essential challenge in investigating their habitability and the possible existence of life on their surfaces. We present a reconstruction method for fractional areas of different surface types from the colors of an Earth-like exoplanet. We create mock light curves for Earth without clouds using empirical data. These

Yuka Fujii; Hajime Kawahara; Yasushi Suto; Atsushi Taruya; Satoru Fukuda; Teruyuki Nakajima; Edwin L. Turner

2010-01-01

67

Rare earth elements as a fingerprint of soil components solubilization  

NASA Astrophysics Data System (ADS)

The retention of rare earth element (REE) in the soil profile are mainly controlled by three factors, (i) the stability of the primary REE-carrying minerals, (ii) the presence of secondary phases as clays and Fe- and Mn-oxyhydroxides and (ii) the concentration of colloidal organic matter (OM). Considering that each soil phases (mineral or organic) displays (ii) various surface properties, such as specific area, surface sites density and nature and (ii) their own REE distribution inherited from the rock weathering, their mobilization through various chemical reactions (dissolution, colloidal release….) may involve the development of various shaped REE patterns in the soil solutions. REE fractionation from the different soil phases may therefore be used to identify the response of the soil system to a particular chemical process such as reductive and/or acidic dissolution. To test this purpose, an organic-rich wetland soil sample was incubated under anaerobic condition at both pH 5 and uncontrolled pH. The REE patterns developed in the soil solution were then compared to the REE patterns obtained through either aerobic at pH 3 and 7 incubations or a chemical reduction experiment (using hydroxylamine). REE patterns in anaerobic and aerobic at pH 7 experiments exhibited the same middle rare earth element (MREE) downward concavity significant of the complexation of REE with soil OM. By contrast, under acidic condition, the REE pattern exhibited a positive Eu anomaly due to the dissolution of soil feldspar. Finally, REE pattern obtained from the chemical reducing experiment showed an intermediary flat shape corresponding to a mixing between the soil organic and mineral phases dissolution. The comparison of the various REE pattern shapes allowed to conclude that (i) biological reduction of wetland soil involved amorphous Fe(III) colloids linked to OM and, (ii) that the REE mobility was controlled by the dynamic of OM in wetland soil. They also evidence the potential of REE to be use as a tracer of the soil phases involved in the various chemical processes running in soil solutions.

Davranche, M.; Grybos, M.; Gruau, G.; Pédrot, M.; Dia, A.

2009-04-01

68

Mass-Independent Fractionation of Oxygen Isotope in Earth Wind: First Principle Calculations for Photodissociation  

Microsoft Academic Search

Mass-independently fractionated oxygen isotope were reported on metal particles extracted from Apollo lunar soils [1, 2], but these origins are still unknown. Since the substantial fraction of Earth-escaping O+ flux (Earth Wind, EW hereafter), comparable to the amount of the anomalous oxygen implanted on the metal particles, could reach the lunar surface [3], Ozima et al. [4] suggested that EW

A. Yamada; S. Nanbu; Y. Kasai; M. Ozima

2009-01-01

69

Concentrations of rare-earth elements in soils of the Prioksko-Terrasnyi state biospheric reserve  

NASA Astrophysics Data System (ADS)

The concentrations of rare-earth elements were studied in the profiles of soddy podburs and mucky-humus gley soils. The soil horizons differed significantly in the contents of Corg (0-26%), the physical clay (<0.01 mm) fraction (3-31%), the acidity (pH 4 to 5.5), and the presence/absence of Al-Fe-humus accumulations. The most significant relationship was observed between the concentrations of rare-earth elements and the physical clay content, particularly for Nd: x(Nd, mg/kg) = 7 + 1.6 y (fraction <0.01 mm, %). Weak biogenic accumulations in the upper horizons were observed for Nd, Ce, and Dy; Nd, Pr, and La accumulated in the Al-Fe-humus illuvial horizon. The concentrations of rare-earth elements in the studied soils formed the following sequence (mg/kg): Nd (20-101)-Ce (10-44)-La, Sm, Gd, Dy, Yb (3-20)-Pr (1-4)-Ho (0.1-0.4)-Tm, Lu, and Tl (0.0). A clear trend was observed to higher contents of even-numbered elements as compared with odd-numbered elements, excluding La.

Perelomov, L. V.; Asainova, Zh. S.; Yoshida, S.; Ivanov, I. V.

2012-10-01

70

Rare earth element chemistry of zircon and its use as a provenance indicator  

Microsoft Academic Search

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

Paul W. O. Hoskin; Trevor R. Ireland

2000-01-01

71

The behaviour of the rare earth elements during mixing of river and sea waters  

Microsoft Academic Search

Rare earth element concentrations have been measured in organic-rich Luce river water and coastal sea water. Concentrations ( e.g. ~350-1850 pmol\\/kg Nd in the Water of Luce and ~45-350 pmol\\/ kg Nd in Luce Bay) are related to the presence of particles, with 30-60% of the REE associated with >0.4-0.7 m particles, and to riverine Fe concentrations. REE fractionation occurs

J. Hoyle; H. Elderfield; A. Gledhill; M. Greaves

1984-01-01

72

Removal of rare earth elements by algal flagellate Euglena gracilis  

Microsoft Academic Search

Removal of rare earth elements (REEs) from an acid solution by an algal flagellate, Euglena gracilis, was studied. Sixteen kinds of REEs were spiked to the solution at a final concentration of 10?gL?1 for each element. E. gracilis cells grown in the solution under 12h light–dark cycles efficiently removed REEs during the 21-day experimental period. Significant removal was observed from

Nobuyoshi Ishii; Keiko Tagami; Shigeo Uchida

2006-01-01

73

Stabilisation of divalent rare earth elements in natural fluorite  

Microsoft Academic Search

Summary  ¶The occurrence of divalent rare earth elements (Sm2+, Yb2+, Tm2+, and Ho2+) in natural fluorite is evaluated using a suite of 37 samples deriving mainly from Sn–W deposits in the Erzgebirge (Germany),\\u000a Central Kazakhstan, and the Mongolian Altai. Trace element composition was determined by ICP-AES and ICP-MS. The defect structure\\u000a of the samples was studied by cathodoluminescence (CL), electron paramagnetic

U. Kempe; M. Plötze; A. Brachmann; R. Böttcher

2002-01-01

74

Trace element variation in size-fractionated African desert dusts  

Microsoft Academic Search

Desert particulate samples from locations in the Sahara–Sahel dust corridor (Western Sahara, Algeria, Chad and Niger) were segregated into size fractions ranging from 20?m and analysed using inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The size-fractionated samples contain higher concentrations of Al, Na, Mg, Fe and most trace elements in the finer, phyllosilicate-rich

Sonia Castillo; Teresa Moreno; Xavier Querol; Andrés Alastuey; Emilio Cuevas; Ludger Herrmann; Mohammed Mounkaila; Wes Gibbons

2008-01-01

75

RARE EARTH ELEMENT SENSITIVITY FACTORS IN CALCIC PLAGIOCLASE (ANORTHITE)  

Microsoft Academic Search

The rare earth elements (REE) are sensitive indicators of the geochemical processes responsible for the evolution of differentiated rocks. Although most measurements are made on bulk samples by a variety of techniques, in recent years the ability to make in situ ion microprobe analyses of the REE on individual minerals within a petrographic context has become increasingly important for understanding

C. Floss; B. Jolliff

76

On the Concentration of Certain Elements at the Earth's Surface  

Microsoft Academic Search

A survey of the abundances of elements in the ocean and sedimentary rocks as compared to their abundances in the weathered igneous rocks shows that carbon, nitrogen, oxygen as water, chlorine, bromine and boron are highly concentrated in the surface materials and that thicknesses of from 17 to 89 km of the outer part of the earth would be required

H. C. Urey

1953-01-01

77

Rare Earth Elements in CI1-Chondrites and Planetary Samples  

NASA Astrophysics Data System (ADS)

We present high-precision LA-ICPMS data about rare earth elements, which show that planetary samples have a Tm-anomaly compared to CI1-chondrites. We conclude that a Tm-rich refractory phase was added to the CI1-chondrites.

Bendel, V.; Pack, A.; O'Neill, H.

2012-03-01

78

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

National Technical Information Service (NTIS)

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

J. C. Laul E. A. Lepel

1986-01-01

79

Rare earth elements as a fingerprint of soil components solubilization  

Microsoft Academic Search

The retention of rare earth element (REE) in the soil profile are mainly controlled by three factors, (i) the stability of the primary REE-carrying minerals, (ii) the presence of secondary phases as clays and Fe- and Mn-oxyhydroxides and (ii) the concentration of colloidal organic matter (OM). Considering that each soil phases (mineral or organic) displays (ii) various surface properties, such

M. Davranche; M. Grybos; G. Gruau; M. Pédrot; A. Dia

2009-01-01

80

Behavior of Rare Earth Elements in Fractured Aquifers  

Microsoft Academic Search

An understanding of the geochemistry of potential host rocks is very important in the site evaluation for construction of an underground geologic repository for radioactive waste. Because of similar valence and ionic radii and high similarity in electronic structure with trivalent actinides (such as Am3+ and Cm3+), the rare earth elements (REEs) have been used to predict the behavior of

S. Lee; Y. Kim; K. Lee

2003-01-01

81

Ternary phosphates of rubidium-cesium-rare earth element  

Microsoft Academic Search

This article examines the possibility of the existence of ternary phosphates of the rare earth elements (REE) containing two large alkali cations in order to establish the morphological and physicochemical characteristics in the entire group of ternary REE phosphates. The synthesis of the ternary rubidium-cesium-REE phosphates was carried out with molten charges that did not contain an excess of components.

P. P. Melnikov; H. D. Carrillo-Eredero; V. A. Efremov; L. N. Komissarova; E. Quiroga

1986-01-01

82

Rare Earth Element Evidence for Paleolake Chemistry  

NASA Astrophysics Data System (ADS)

The Eocene Green River Formation contains lacustrine deposits famous for their oil shales, fish fossils and cyclic nature. Although there are common trends in the facies and types of authigenic minerals seen in progressive lake phases and among the different lake basins, there are also distinct differences. These differences illustrate that the basins were not connected through at least part of their history. The common trends throughout the sequences and from all the basins include: 1) elevated alkalinity; 2) cycles that reflect contraction (elevated salinity) and expansion (freshening); and 3) sedimentary structures that allow us to place facies in a limno-geologic context. A key goal is to relate the facies to the paleo-lake chemistry. This requires comparison to modern lakes where similar facies are being created coupled with an integration of the chemistry of the fluids and the trace element patterns in the authigenic minerals. REE patterns from the Great Basin Lake waters are HREE enriched and show trends of increased REE concentrations that have been linked directly to alkalinity (Johannesson et al., 1994). Authigenic phases from facies that reflect lowstands, transgression and highstands in the Green River Formation have patterns that can be directly compared to those from the Great Basin Lake waters. This illustrates great potential for constraining the alkalinity of the precipitating fluids. Although the Kd of the authigenic minerals for the REE's has to be considered before conclusive models can be proposed, there are impressive similarities between REE patterns of authigenic phases from the Green River Formation and waters of modern alkaline lakes of the Great Basin.

Hemming, N. G.; Rasbury, E. T.

2004-12-01

83

Fractional generalization of memristor and higher order elements  

NASA Astrophysics Data System (ADS)

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

Tenreiro Machado, J.

2013-02-01

84

Miocene Coral Skeleton Rare Earth Element Patterns Reflect River Discharge  

NASA Astrophysics Data System (ADS)

Rare Earth Element (REE) patterns of modern coral skeletons usually reflect the REE composition of ambient seawater which is characterized by heavy REE enriched relative to light REE with NASC (North American Shale Composite) normalized La/Lu ratios of typically <0.4. The REE concentration in coral aragonite is enriched by 3 to 4 orders of magnitude compared to ambient seawater. Here we report trace element data including REE of coral skeletons of Late Miocene age (~9 Ma, Tortonian) from Crete (Eastern Mediterranean). Analyses were done using a 213 nm Nd:YAG laser coupled to an Element2 ICP-MS along the growth axis of the coral skeletons. The profiles show that Ba/Ca ratios have a seasonally induced pattern with high values around the winter months which are identified by ?18O analyses. REE/Ca ratios co-vary with Ba/Ca ratios. Since the Ba/Ca ratio is a proxy used to monitor river discharge, the co-variation suggests the REE/Ca ratio to be a proxy of comparable quality. NASC-normalized REE patterns of the Tortonian corals have negative Ce anomalies like modern corals. However, the Tortonian corals have REE patterns highly enriched in LREE with (La/Lu)N ratios of 4 to 30 which is 1 to 2 orders of magnitude higher compared to modern corals. Al concentrations are low (<10 ppm) and do not correlate with REE concentrations indicating an insignificant fraction of terrigenous material included in the skeleton. Applying distribution coefficients typical for modern corals, the REE composition of the Tortonian ambient water yields (La/Lu)N of about 2 to 16. This range can be explained by binary mixing of modern Eastern Mediterranean sea surface water ((La/Lu)N=0.35, sea surface salinity (SSS) ~38 ‰) with highly LREE-enriched river water ((La/Lu)N >3, salinity ~0.5 ‰) transporting suspended and colloid phases, also highly enriched, especially in LREE, at a ratio of ~9 (seawater):1 (river water). The river water component is considered because paleoenvironmental reconstructions suggest the reef to have grown close to a river mouth. The calculated mixing ratio corresponds to a SSS of the ambient water >34 ‰ compatible with environmental conditions favorable for coral growth. As possible sources of the REE transported by river water, weathering products of Cretan hinterland rocks must be considered. During the Miocene, drained hinterland was formed by a diversity of magmatic, metamorphic and sedimentary lithologies, essentially represented by granitoids, ophiolitic rocks, siliciclastic sediments and carbonates. A detailed identification of sources as well as quantification of corresponding fractions of REE contributing to the bulk river water component is principally possible in cases where the drained system shows a more limited variation in rock lithologies, however, is difficult to apply to the complex Cretan situation. This study demonstrates that the REE patterns of coral skeletons can be suitable to reconstruct the bulk REE composition of the drainage system in the reef’s hinterland. Also, we suggest to use REE/Ca and Ba/Ca ratios likewise in order to identify fluctuations in river discharge to marine environments.

Mertz-Kraus, R.; Brachert, T. C.; Jochum, K. P.

2010-12-01

85

Rare earth element partition coefficients in zircon/melt systems  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

86

Interactions of rare earth elements with bacteria and organic ligands  

Microsoft Academic Search

We investigated the interactions of rare earth elements (REEs) Eu(III) and\\/or Ce(III, IV) with the common soil bacterium Pseudomonas fluorescens and organic ligands, such as malic acid, citric acid, a siderophore (DFO), cellulose, chitin, and chitosan. Malic acid formed complexes with Eu(III), but degradation of malic acid was observed when the ratio of malic acid to Eu(III) was higher than

Takuo Ozaki; Yoshinori Suzuki; Takuya Nankawa; Takahiro Yoshida; Toshihiko Ohnuki; Takaumi Kimura; Arokiasamy J. Francis

2006-01-01

87

Rare-earth element geochemistry of Madras granulites  

Microsoft Academic Search

Archaean granulites from the type charnockite locality of Pallavaram, Madras City, Tamil Nadu, southern India consist of a\\u000a bimodal suite of basic and silicic orthogneisses, associated with metasedimentary gneisses (khondalites). Charnockite is the\\u000a dominant rock type.\\u000a \\u000a Basic granulites display a tholeiitic trend of strong iron enrichment accompanied by an increase in the concentration of the\\u000a rare earth elements (REE), and

Barry L. Weaver

1980-01-01

88

Experimental evidence of rare earth element immobility in greenstones  

Microsoft Academic Search

Significant petrogenetic importance has recently been placed on the Nd isotopic composition and variable rare earth element (REE) content of basalts, although the effect of alteration on the REE has not been fully investigated. REE analyses of oceanic1-6 and ophiolitic basalts7,8 suggest that the light REE (La, Ce, Nd, Sm, Eu) are mobile during basalt-seawater interaction at relatively low temperatures.

Martin Menzies; William Seyfried; Douglas Blanchard

1979-01-01

89

Energy-adjusted pseudopotentials for the rare earth elements  

Microsoft Academic Search

Nonrelativistic and quasirelativistic energy-adjusted pseudopotentials and optimized (7s6p5d)\\/[5s4p3d]-GTO valence basis sets for use in molecular calculations for fixed f-subconfigurations of the rare earth elements, La through Lu, have been generated. Atomic excitation and ionization energies from numerical HF, as well as SCF pseudopotential calculations using the derived basis sets, differ by less than 0.1 eV from numerical HF all-electron results.

M. Dolg; H. Stoll; A. Savin; H. Preuss

1989-01-01

90

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

Microsoft Academic Search

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

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

2005-01-01

91

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

Microsoft Academic Search

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

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

2006-01-01

92

Uncovering the Global Life Cycles of the Rare Earth Elements  

NASA Astrophysics Data System (ADS)

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

Du, Xiaoyue; Graedel, T. E.

2011-11-01

93

Uncovering the global life cycles of the rare earth elements.  

PubMed

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, 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

2011-11-04

94

Accumulation of rare earth elements by siderophore-forming Arthrobacter luteolus isolated from rare earth environment of Chavara, India.  

PubMed

In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed. PMID:22357200

Emmanuel, E S Challaraj; Ananthi, T; Anandkumar, B; Maruthamuthu, S

2012-03-01

95

Melted Murataite Ceramics Containing Simulated Actinide/Rare Earth Fraction of High Level Waste  

SciTech Connect

Murataite-based ceramics with three different chemical compositions containing simulated actinide/rare earth (RE) fraction of HLW were produced in a resistive furnace at a temperature of 1500 deg. C and two of them - in a cold crucible energized from a 5.28 MHz/10 kW high frequency generator. All the samples prepared in resistive furnace were composed of major murataite and minor perovskite, crichtonite, zirconolite, and pyrophanite/ilmenite. The samples produced in the cold crucible were composed of murataite, perovskite, crichtonite, and rutile. Higher content of perovskite and crichtonite in the cold crucible melted ceramic than in the ceramic with the same chemical composition but melted in resistive furnace may be due to higher temperature in the cold crucible (up to 1600-1650 deg. C) at which some fraction of murataite was subjected to decomposition yielding additional amount of perovskite and crichtonite. Method of melting may effect on elemental partitioning in the murataite-containing ceramics because light (Ce-group) REs enter preferably perovskite phase whereas Nd, Sm, and heavy (Y-group) REs are accommodated in the murataite polytypes. Thus, perovskite and murataite are major host phases for the Ce- and Y-group REs, respectively, whereas tetravalent actinides (U) enter murataite only.

Stefanovsky, S.V.; Ptashkin, A.G.; Knyazev, O.A.; Zen'kovskaya, M.S.; Stefanovsky, O.I. [State Unitary Enterprise SIA Radon, Moscow (Russian Federation); Yudintsev, S.V.; Nikonov, B.S.; Lapina, M.I. [Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian, Academy of Sciences (IGEM RAS), Moscow (Russian Federation)

2008-07-01

96

Which geodynamic roles for volatile-rich low melt fractions in the Earth's mantle?  

NASA Astrophysics Data System (ADS)

Volatiles and melts are thoroughly related in the Earth's mantle because volatiles facilitate melting and melts concentrate mantle volatiles. Mapping of mantle solidus by mean of experimental petrology has long established that melting can occur in numerous mantle regions provided that volatiles are present in the rocks. Volatile concentration in mantle rocks is however small and consequently, associated melt fractions are small. The produced liquids are carbonated melts, which can incorporate variable amount of silicate components and are extremely rich in volatiles (H-Cl-F-S). Because melting profoundly affects rock physical properties and geochemical mass transfers, the localization and recognition of such melts inside the Earth are critical for our understanding of global mantle geodynamics. Mantle electrical conductivity, rather than seismic methods is most suited to identify the presence of such low melt fractions, because low melt fraction likely to form at depth > 150 km are expected to constitute about 0.1% at the grain boundaries of mantle rocks. Recent electromagnetic surveys (see Tarits et al. this meeting) indicate that underneath Mid-Oceanic Ridges, mantle rocks are continuously conductive from 60 km, the depth of MOR-basalt formation, to >400 km depth. Such conductive mantle rocks are clearly attributed to small fractions of carbonated melts, which furthermore most likely contain high amounts of water (see Sifré and Gaillard, this session). This petrological interpretation of mantle electrical anomalies contrasts with the traditional mineral physic views that attributed high mantle conductivity to crystallographic defects associated to water incorporation in olivine. But the water in olivine model is disputed by nearly all existing experimental data. The amount of carbonated melts required to explain mantle conductivity suggests about 170-300 ppm CO2 in the mantle that sources MOR-basalts, which is in excellent agreement with geochemical estimations (180 +/- 100 ppm). The geochemical-geodynamic implications of continuous melt films wetting grain boundaries from the transition zone the MOR-basalt source regions are then discussed following several key observations: (1) The redox transition from carbonate to diamond expected from petrological models to occur at 200-250 km depth is not consistent with geophysical observations implying a revision of mantle redox state in up-welling regions; (2) The petrologically assessed depth of anhydrous melting of carbonate is 350km but high conductivity extends well below, implying a likely hydrous melting of mantle carbonates; (3) A continuous network of low melt fractions from the transition zone to the MOR-B melting regions has major implications regarding the rate of transfer of incompatible elements from the transition zone to the lithosphere-asthenosphere boundary, which might be faster than mantle convection rates; (4) these incompatible elements include volatile species such as water, which would not only sit in olivine and radioactive elements, implying that an important mantle heat source is in fact mobile.

Gaillard, F.

2012-04-01

97

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

NASA Astrophysics Data System (ADS)

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 peridotites are residual in rare-earth character, but cannot be clearly related to the overlying mafic rocks. Chromian spinel is probably insignificant in its effect on REE distribution during partial melting and crystal fractionation, as indicated by the low REE concentrations in chromitite from the Samail. Layered gabbro REE patterns are dominated by cumulus clinopyroxene and plagioclase. Large positive Eu anomalies demonstrate plagioclase accumulation. Modal mixing (mass balance) calculations reveal that most of these adcumulus gabbros have REE patterns that are the products of the REE concentrations of their constituent cumulus phases in the observed modal proportions; hence no appreciable REE-rich mesostasis is present. Such calculations also allow the prediction of mineral REE concentrations not actually determined by mineral separate analyses. Several high-level (noncumulus?) gabbros yield patterns with positive Eu anomalies suggesting relative plagioclase accumulation, probably due to liquid fractionation (filter pressing). Dike complex REE patterns show light rare-earth element depletions and are similar to, but not necessarily diagnostic of, midocean ridge basalt. They cluster at similar abundance levels; however, the absolute variation in abundance is large, indicative of modification by crystal fractionation. Calculations using partition coefficient data indicate that many dikes represent liquids that could have existed in equilibrium with cumulus minerals of the plutonic suite. Mineral separate REE data from layered cumulus gabbro of the Khafifah stratigraphic section reveal cryptic variation trends that are correlated with major element variation, in support of a long-lived (periodically replenished) magma chamber model (Pallister and Hopson, 1978, 1979, 1981). (Cryptic variation as used herein is defined as the change in mineral composition with respect to stratigraphic position.) The REE cryptic variation shows both direct and inverse correlation to major element variation, indicating that magmatic replenishment was complicated by changes in parent melt REE abundance. A crystal fractionation origin for the small plagiogranite bodies of the Ibra area is favored by REE modeling, although larger bodies (Dasir) may also be related to magmatic inclusion of roofrock with diabase level REE distribution (Gregory and Taylor, 1979).

Pallister, John S.; Knight, Roy J.

1981-04-01

98

Bibliography on Rare-Earth Elements (Including Scandium and Yttrium) 1958-1962.  

National Technical Information Service (NTIS)

Contents: General research on rare-earth elements (REEs); Atom and crystal structure of metals and REE compounds; Physical properties of REE metals and their alloys; Physical properties of compounds of RE element; Properties of isotopes of RE elements (Nu...

K. E. Mironov L. A. Chernikova

1970-01-01

99

Rare-Earth Elements and Their Position in the Periodic System.  

National Technical Information Service (NTIS)

Contents: Previous history and the origin of problem of rare earths; History of rare-earth elements after the discovery of periodic law; Problem of position of rare-earth elements in the table in the chemical stage of development of periodic law; Physical...

D. N. Trifonov

1970-01-01

100

EXAFS study of rare-earth element coordination in calcite  

NASA Astrophysics Data System (ADS)

Extended X-ray absorption fine-structure (EXAFS) spectroscopy is used to characterize the local coordination of selected rare-earth elements (Nd 3+ , Sm 3+ , Dy 3+ , Yb 3+ ) coprecipitated with calcite in minor concentrations from room-temperature aqueous solutions. Fitting results confirm substitution in the Ca site, but first-shell Nd-O and Sm-O distances are longer than the Ca-O distance in calcite and longer than what is consistent with ionic radii sums for sixfold coordination in the octahedral Ca site. In contrast, first-shell Dy-O and Yb-O distances are shorter than the Ca-O distance and are consistent with ionic radii sums for sixfold coordination. Comparison of Nd-O and Sm-O bond lengths with those in lanthanide sesquioxides and with ionic radii trends across the lanthanide series suggests that Nd 3+ and Sm 3+ have sevenfold coordination in a modified Ca site in calcite. This would require some disruption of the local structure, with an expected decrease in stability, and possibly a different charge compensation mechanism between Nd and Sm vs. Yb and Dy. A possible explanation for the increased coordination for the larger rare-earth elements involves bidentate ligation from a CO 3 group. Because trivalent actinides such as Am 3+ and Cm 3+ have ionic radii similar to Nd 3+ , their incorporation in calcite may result in a similar defect structure.

Elzinga, E. J.; Reeder, R. J.; Withers, S. H.; Peale, R. E.; Mason, R. A.; Beck, K. M.; Hess, W. P.

2002-09-01

101

Colors of a Second Earth: Estimating the Fractional Areas of Ocean, Land, and Vegetation of Earth-like Exoplanets  

NASA Astrophysics Data System (ADS)

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

Fujii, Yuka; Kawahara, Hajime; Suto, Yasushi; Taruya, Atsushi; Fukuda, Satoru; Nakajima, Teruyuki; Turner, Edwin L.

2010-06-01

102

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

SciTech Connect

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

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

2010-06-01

103

The Significance of Rare Earth Element Partition Coefficients in Zircon  

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

104

Calculation of binary phase diagrams between the actinide elements, rare earth elements, and transition metal elements.  

National Technical Information Service (NTIS)

Attempts were made to apply the Kaufman method of calculating binary phase diagrams to the calculation of binary phase diagrams between the rare earths, actinides, and the refractory transition metals. Difficulties were encountered in applying the method ...

J. E. Selle

1992-01-01

105

Behavior of Rare Earth Elements in Fractured Aquifers  

NASA Astrophysics Data System (ADS)

An understanding of the geochemistry of potential host rocks is very important in the site evaluation for construction of an underground geologic repository for radioactive waste. Because of similar valence and ionic radii and high similarity in electronic structure with trivalent actinides (such as Am3+ and Cm3+), the rare earth elements (REEs) have been used to predict the behavior of actinide-series elements in solution. For Am and Cm, which occur only in the trivalent states in most waste-disposal repository environments, the analogy with the REEs is particularly relevant. Krauskopf calculated the retardation factors for radionuclides in various rock materials based on some compiled data. But, in general, because the transuranic actinides do not occur naturally in appreciable quantities, their behaviors in repository environments cannot be predicted from evidence of their movement in geologic environments (mainly in groundwater) over geologic timespans. Predictions about long-term future behavior of transuranic actinides have therefore been made by extrapolation from short-term observations of their chemical properties in laboratory experiments or in field tests, but such extrapolation is fraught with uncertainty. In order to verify the behavior of Eu in various geological environments, we estimated the abundance of rare earth elements in three gneiss bodies originated from different geological environments and volcanic tuff. We also carried out some leaching experiment of fracture-filling calcite precipitated due to changes of geochemical environment in paleo-groundwater. Of the three gneisses, two gneisses are granitic-granodioritic origin and the other is tonaltic-trondjemitic origin. As a result, we could observe that Eu had a close relationship with fracture-filling calcite precipitation due to water-rock interaction. Our results show that Eu is the most variable element of REEs for the hydrogeological environment such as change of oxidation-reduction and petrography. The similarity in physical and chemical properties between REEs and actinides shows well in the cohesive energy diagram against the REEs and actinides. In addition, the ionic radii of Eu2+, Eu3+, Am2+ and Am3+ at CN= 8 and 9 are summarized. They have very similar ionic radii in di- and trivalent ionic state. This suggests that they may be very similar behavior in geological states. In conclusion, the fracture-filling calcite and REE is a good tool in understanding the changes of geochemical environments in paleo-groundwater as well as an analogue for actinide elements.

Lee, S.; Kim, Y.; Lee, K.

2003-12-01

106

BIOGEOCHEMISTRY OF THE RARE-EARTH ELEMENTS WITH PARTICULAR REFERENCE TO HICKORY TREES  

Microsoft Academic Search

Hickory trees concentrate the rare-earth elements in their leaves to a ; phenomenal degree and may contain as much as 2300 ppm of total rare earths based ; on the dry weight of the leaves. The average proportions of the individual ; elements (atomic percent of the total rareearth elements) in the leaves are: Y ; 36, La 16, Ce

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

1958-01-01

107

Revisiting the rare earth elements in foraminiferal tests [rapid communication  

NASA Astrophysics Data System (ADS)

Are the rare earth elements (REEs) in foraminifera a valuable proxy for use in paleoceanographic and climate change studies? In order to investigate this, we attempted a comprehensive study of REEs in planktonic and benthic foraminifera. Several different cleaning protocols were tested. Although the hydroxylamine used to clean all foraminifera in this study removes an unidentified source of REE contamination, it seems to remobilize metal oxides that are otherwise unaffected in flow-through dissolution. The calculated REE distribution coefficients, KD(REE)s, are between 100 and 500 for both planktonic and benthic foraminifera. These KDs are high compared to other elements in biogenic calcite but can be explained through a general model of element incorporation during foraminiferal calcification. From data taken from eight core tops in the southeast Pacific, we conclude that the REEs in planktonic foraminifera are, indeed, useful as a proxy for upper ocean water mass and mixed layer biogenic productivity. Alternatively, the REEs in benthic foraminifera are useful as a proxy for carbon flux to the sea floor. These proxies should be robust down core unless the sediments have undergone anoxic diagenesis, which stabilizes Fe carbonate thus overprinting the primary REE signature. However, it is clear from REE distributions in foraminiferal tests if anoxic conditions have occurred.

Haley, Brian A.; Klinkhammer, Gary P.; Mix, Alan C.

2005-10-01

108

Ternary phosphates of rubidium-cesium-rare earth element  

SciTech Connect

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

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

1986-06-01

109

Obtaining the spectra of rare-earth elements in their direct determination in minerals  

Microsoft Academic Search

The aim of the present investigation was to develop a method for the direct quantitative determination of rare-earth elements present in various relationships in minerals, For an arbitrary ratio of the base elements (these not belonging to the rare-earth group). In order to create favorable conditions for the passage of individual rare-earth elements into the discharge we studied a number

O. A. Kul'skaya; R. N. Shkvaruk; S. A. Kozak

1971-01-01

110

[Physiological effects of rare earth elements and their application in traditional Chinese medicine].  

PubMed

The process in the studies on physiological effects of rare earth elements in plants and their action mechanisms were summarized in the aspects of seed germination, photosynthesis, mineral metabolism and stress resistance. And the applications of rare earth elements in traditional Chinese medicine (TCM) in recent years were also overviewed, which will provide reference for further development and application of rare earth elements in TCM. PMID:23189726

Zhou, Jie; Guo, Lanping; Xiao, Wenjuan; Geng, Yanling; Wang, Xiao; Shi, Xin'gang; Dan, Staerk

2012-08-01

111

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

112

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

NASA Astrophysics Data System (ADS)

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 REE in biogenic apatite of Recent fish debris occurs near the sediment-water interface soon after deposition and reflects characteristics of seawater. The original REE signature apparently survives subsequent burial and diagenesis. Cerium variations in fish debris from modern environments are controlled by redox potential. Ce is fractionated by co-precipitation with metallic oxides under oxidizing conditions. This fractionation produces a negative Ce anomaly (Ce anom ) in seawater that is reflected in the sedimented fish debris. Conversely, no fractionation of Ce occurs under reducing conditions, resulting in Ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions. Extrapolation of observations of the redox control of Ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower Paleozoic and Lower Triassic oceans, whereas in the upper Paleozoic, the world ocean was generally oxidizing.

Wright, Judith; Schrader, Hans; Holser, William T.

1987-03-01

113

Geochemistry of the Rare Earth elements in spilites from the oceanic and continental crust  

Microsoft Academic Search

Analytical data including major elements, the Rare Earths, Ni, Cu, Zn, Rb, and Sr are presented for twenty-three spilites from the Mid-Atlantic Ridge, the Hercynian part of the Variscan geosyncline in Germany, and several localities in Switzerland. Low grade metamorphism (up to approximately 400° C) and spilitization of basaltic rocks apparently do not alter the original Rare Earth element (REE)

Albert Günter Herrmann; Mark J. Potts; Doris Knake

1974-01-01

114

Separation and determination of traces of rare earth elements in nickel- base alloys and aluminum alloys  

Microsoft Academic Search

A new method for extraction of rare earth elements in nickelbase alloys ; and aluminum alloys is presented. The masking agent used is composed of 100 M of ; 60% thiocyanate, 10 ml of 60% sulfosalicylic acid, 120 ml of pH 5.5 acetate, and ; 370 ml of water. PMBP is used to separate the rare earth elements. The effects

Peng

1973-01-01

115

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

National Technical Information Service (NTIS)

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

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

1995-01-01

116

FRACTIONAL DISTILLATION SEPARATION OF PLUTONIUM VALUES FROM LIGHT ELEMENT VALUES  

DOEpatents

A process is described for removing light element impurities from plutonium. It has been found that plutonium contaminated with impurities may be purified by converting the plutonium to a halide and purifying the halide by a fractional distillation whereby impurities may be distilled from the plutonium halide. A particularly effective method includes the step of forming a lower halide such as the trior tetrahalide and distilling the halide under conditions such that no decomposition of the halide occurs. Molecular distillation methods are particularly suitable for this process. The apparatus may comprise an evaporation plate with means for heating it and a condenser surface with means for cooling it. The condenser surface is placed at a distance from the evaporating surface less than the mean free path of molecular travel of the material being distilled at the pressure and temperature used. The entire evaporating system is evacuated until the pressure is about 10/sup -4/ millimeters of mercury. A high temperuture method is presented for sealing porous materials such as carbon or graphite that may be used as a support or a moderator in a nuclear reactor. The carbon body is subjected to two surface heats simultaneously in an inert atmosphere; the surface to be sealed is heated to 1500 degrees centigrade; and another surface is heated to 300 degrees centigrade, whereupon the carbon vaporizes and flows to the cooler surface where it is deposited to seal that surface. This method may be used to seal a nuclear fuel in the carbon structure.

Cunningham, B.B.

1957-12-17

117

Clinopyroxene-orthopyroxene major and rare earth elements partitioning in spinel peridotite xenoliths from Assab (Ethiopia)  

Microsoft Academic Search

Major element and rare earth element (REE) partitioning among coexisting clinopyroxene-orthopyroxene pairs from mantle xenoliths of the Assab Range (Ethiopia) are discussed in terms of crystal-chemistry. Major element partitioning indicates relatively uniform conditions of subsolidus equilibration over a narrow range of temperatures (mean value about 1100 C) in the spinel peridotite stability field. Major element distributions and correlations, moreover, seem

G. Ottonello; G. B. Piccardo; A. Mazzucotelli; F. Cimmino

1978-01-01

118

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

Microsoft Academic Search

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

R. C. Price; S. R. Taylor

1977-01-01

119

Elemental Analysis of Human Serum and Serum Protein Fractions by Thermal Neutron Activation.  

National Technical Information Service (NTIS)

Some acplications of thermal neutron activation for the determination of elemental contents in human serum and human serum protein fractions are presented. First total serum is dealt with; second serum protein fractions obtained by gel filtration are desc...

J. R. W. Woittiez

1984-01-01

120

Light elements in the Earth's core: Fe3X compounds  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

121

Speciation of adsorbed yttrium and rare earth elements on oxide surfaces  

NASA Astrophysics Data System (ADS)

The distribution of yttrium and the rare earth elements (YREE) between natural waters and oxide mineral surfaces depends on adsorption reactions, which in turn depend on the specific way in which YREE are coordinated to mineral surfaces. Recent X-ray studies have established that Y 3+ is adsorbed to the rutile (1 1 0) surface as a distinctive tetranuclear species. However, the hydrolysis state of the adsorbed cation is not known from experiment. Previous surface complexation models of YREE adsorption have suggested two to four cation hydrolysis states coexisting on oxide surfaces. In the present study, we investigate the applicability of the X-ray results to rare earth elements and to several oxides in addition to rutile using the extended triple-layer surface complexation model. The reaction producing a hydrolyzed tetranuclear surface species 4>SOH+M+2HO=(>SOH)2_M(OH)2++4H was found to account for a significant fraction of the adsorbed Y 3+, La 3+, Nd 3+, Gd 3+, and Yb 3+ on rutile, hematite, alumina and silica over wide ranges of pH and ionic strength. Where adsorption data were available as a function of surface coverage for hematite and silica, an additional reaction involving a mononuclear species could be used to account for the higher surface coverages. However, it is also possible that some of the higher surface coverage data refer to surface precipitation rather than adsorption. The results of the present study provide an internally consistent basis for describing YREE adsorption which could be used to investigate more complex systems in which YREE compete both in aqueous solution and on mineral surfaces with alkaline earths and ligands such as carbonate, sulfate, chloride and organic species, in order to build a predictive adsorption model applicable to natural waters.

Piasecki, Wojciech; Sverjensky, Dimitri A.

2008-08-01

122

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

123

Colloidal rare earth elements in a boreal river: Changing sources and distributions during the spring flood  

NASA Astrophysics Data System (ADS)

Variations in the physico-chemical speciation of the rare earth elements (REE) have been investigated in a subarctic boreal river during an intense spring flood event using prefiltered (<100 ?m) samples, cross-flow (ultra)filtration (CFF), flow field-flow fractionation (FlFFF), and diffusive gradients in thin films (DGT). This combination of techniques has provided new information regarding the release and transport of the REE in river water. The colloidal material can be described in terms of two fractions dominated by carbon and iron, respectively. These two fractions, termed colloidal carrier phases, showed significant temporal changes in concentration and size distribution. Before the spring flood, colloidal carbon concentrations were low, the colloids being dominated by relatively large iron colloids. Colloidal concentrations increased sharply during the spring flood, with smaller carbon colloids dominating. Following the spring flood, colloidal concentrations decreased again, smaller carbon colloids still dominating. The REE are transported mainly in the particulate and colloidal phases. Before the spring flood, the REE composition of all measured fractions was similar to local till. During the spring flood, the REE concentrations in the colloidal and particulate fractions increased. The increase was most marked for the lighter REE, which therefore showed a strong enrichment when normalized to local till. Following the spring flood, the REE concentrations decreased again and reverted to a distribution similar to local till. These changes in the concentration and distributions of carbon iron and REE are interpreted in terms of changing hydrological flow paths in soil and bedrock which occur during the spring flood.

Andersson, Karen; Dahlqvist, Ralf; Turner, David; Stolpe, Björn; Larsson, Tobias; Ingri, Johan; Andersson, Per

2006-07-01

124

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

125

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

126

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

USGS Publications Warehouse

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

Birdwell, Justin E.

2012-01-01

127

Chemical Fractionation of Trace Elements in Biosolid?Amended Soils and Correlation with Trace Elements in Crop Tissue  

Microsoft Academic Search

A previous study indicated that agricultural biosolid applications increased the concentration of EPA3050?digestible trace elements in soils on Pennsylvania production farms but could not indicate potential trace?element environmental availability. This study was conducted to determine if biosolid application had altered the distribution of trace?elements among operationally defined soil fractions and the relationship of trace element concentrations in soil and crop

Amy L. Shober; Richard C. Stehouwer; Kirsten E. MacNeal

2007-01-01

128

Analysis for the rare-earth elements by neutron activation and Ge(Li) spectrometry  

Microsoft Academic Search

A procedure for analysis of 12 of the rare-earths, tested on more than a hundred samples of rocks and minerals, is described.\\u000a Carrier is added for each element to be determined. Samples are fused with Na2O2. The rare-earths are separated as a group, then precipitated and mounted as oxalates for Ge(Li) spectrometry. Following radioassay,\\u000a chemical yields for the individual rare-earths

E. B. Denechaud; P. A. Helmke; L. A. Haskin

1970-01-01

129

Input impedance and gain of monopole elements with disk ground planes on flat earth  

Microsoft Academic Search

This paper extends previously reported results for a quarterwave monopole element on a disk ground plane in free space to the case where the disk ground plane rests on flat earth. Numerical results are obtained by utilizing Richmond's method of moments computer program for disk ground planes over flat earth.

M. M. Weiner

1990-01-01

130

Rare earth elements as provenance indicators in North Australian estuarine and coastal marine sediments  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) in three grain size fractions of clay-dominated estuarine and coastal sediments from the North Australian coastline have been investigated for use as potential provenance indicators. Comparisons of data based on instrumental neutron activation analysis and inductively coupled plasma mass spectrometry revealed that HF digestions of zircon-bearing samples resulted in unsatisfactory recovery of REE. Instead, a relatively simple, fast and safe partial digestion using HClO 4 + HNO 3 was used to extract REE mainly from clay minerals while excluding extraction of REE from zircons. A comparison with published data for primary rock units within river catchments showed that the main REE systematics has been preserved in downstream clay-rich sediments. Analysis of variance of La/Gd (PAAS), La/Yb (PAAS) and Eu/Eu* (PAAS) ratios in five areas showed that the <63 ?m fraction possessed the greatest discriminating power. All five areas could be distinguished from each other at highly significant levels based on one or more of these ratios.

Munksgaard, Niels Crosley; Lim, Kezia; Parry, David Livingstone

2003-06-01

131

Axial Symmetry of Linear Structural Elements of the Earth'S Crust (Osevaya Simmetriya Lineynykh Strukturnykh Elementov Zemnoikory).  

National Technical Information Service (NTIS)

The strikes of foldings and faults characterize the non-uniformity in the structure of the terrestrial crust and the anistropy of its stability. The exposure of regularities in spatial distribution of these linear structural elements of the earth's crust ...

A. V. Dolitskii

1968-01-01

132

Effect of Rare Earth Elements on Anisotropy and Microstructure of Al-Li Alloy 2195 Sheets  

Microsoft Academic Search

For the purpose of decreasing the applied limitation resulting from the anisotropic mechanical property of Al-Li alloy 2195, this study employed a complex heat treatment process, involving the pre-tension, thermo-infiltration of the rare earth element Ce, solution treatment, and artificial aging technology. The results indicate that the infiltration of rare earth element Ce benefits the abatement of anisotropy of Al-Li

Xu Yue; Geng Jiping; Liu Yufeng

2006-01-01

133

Research of the entry of rare earth elements Eu 3+ and La 3+ into plant cell  

Microsoft Academic Search

Whether rare earth elements can enter into plant cells remains controversial. This article discusses the ultracellular structural\\u000a localization of lanthanum (La3+) and europium (Eu3+) in the intact plant cells fed by rare earth elements Eu3+ and La3+. Eu-TTA fluorescence analysis of the plasmalemma, cytoplast, and mitochondria showed that Eu3+ fluorescence intensities in such structures significantly increased. Eu3+ can directly enter

Yongsheng Gao; Fuli Zeng; An Yi; Shi Ping; Lanhua Jing

2003-01-01

134

Performance of lead iodide nuclear radiation detectors with the introduction of rare earth elements  

NASA Astrophysics Data System (ADS)

Lead iodide has been recognized as a promising material for room temperature radiation detectors. It has a wide band-gap (˜ 2.3 eV), high atomic numbers (82, 53) and it is environmentally very stable compared to mercuric iodide. Electrical and optical properties of lead iodide grown crystals purified under the influence of selected rare earth elements have been investigated. Photo-luminescence and capacitance-voltage measurements have been performed using different rare earth elements.

Hassan, Mahmoud; Matuchova, Marie; Zdansky, Karel

2006-01-01

135

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

2012-10-22

136

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

137

Magnetism of silicon doped with alkaline earth elements  

NASA Astrophysics Data System (ADS)

It would be highly desirable to fashion spintronic materials based on silicon because of the vital importance of silicon in semiconductor technology. Since it is very difficult to experimentally dope transition metals into silicon, we explore the possibility of ferromagnetism in silicon doped with alkaline earth atoms using first-principle calculations. It is found that the energy needed for doping a calcium atom into silicon is approximately equivalent to the formation energy of a vacancy in silicon. Neither silicon nor any alkaline earth metal alone is magnetic, but our calculations indicate that ferromagnetism may be obtained by appropriately doping silicon with alkaline earth atoms such as calcium. This is intriguing for basic understanding of magnetism and for possible future applications.

Liu, Bang-Gui; Shi, Li-Jie; Louie, Steven G.

2005-03-01

138

Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures  

Microsoft Academic Search

Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000°C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used

Johnson R. Haas; Everett L. Shock; David C. Sassani

1995-01-01

139

An improved description of the interactions between rare earth elements and humic acids by modeling: PHREEQC-Model VI coupling  

NASA Astrophysics Data System (ADS)

The Humic Ion Binding Model VI (Model VI) - previously used to model the equilibrium binding of rare earth elements (REE) by humic acid (HA) - was modified to account for differences in the REE constant patterns of the HA carboxylic and phenolic groups, and introduced into PHREEQC to calculate the REE speciation on the HA binding sites. The modifications were shown to greatly improve the modeling. They allow for the first time to both satisfactorily and simultaneously model a large set of multi-REE experimental data with the same set of equations and parameters. The use of PHREEQC shows that the light rare earth elements (LREE) and heavy rare earth elements (HREE) do not bind to HA by the same functional groups. The LREE are preferentially bound to carboxylic groups, whereas the HREE are preferentially bound to carboxy-phenolic and phenolic groups. This binding differentiation might lead to a fractionation of REE-HA patterns when competition between REE and other metals occur during complexation. A survey of the available data shows that competition with Al 3+ could lead to the development of HREE-depleted HA patterns. This new model should improve the hydrochemical modeling of the REE since PHREEQC takes into account chemical reactions such as mineral dissolution/precipitation equilibrium and redox reactions, but also models kinetically controlled reactions and one-dimensional transport.

Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Bouhnik-Le Coz, Martine; Dia, Aline

2011-10-01

140

Analysis of Fractional Element of Viscoelastic Fluids Using Heaviside Operational Calculus  

NASA Astrophysics Data System (ADS)

Fractional element model describes a special kind of viscoelastic fluids. Its stress is proportional to the fractional-order derivatives of strain. Physically the mechanical analogues of fractional elements can be represented by self-similarity spring-dashpot fractal networks (see Figure 1). In this paper we introduce a constitutive operator in the constitutive equations of viscoelastic fluids. To derive constitutive operators for self-similarity spring-dashpot fractal networks we use Heaviside fractional calculus, which provides explicit answers not otherwise obtainable as simple. Then a constitutive equation of fractional element with 1/2-order derivative was derived. Finally we find the way to derive the constitutive equation with other fractional-order derivatives and its physical analogy.

Zhu, K. Q.; Hu, K. X.; Yang, D.

141

Radial integrals for the magnetic form factor of the 5d electrons of rare earth elements.  

PubMed

The radial integrals , where L = 0, 2, 4, for several electronic configurations of the 5d electrons of rare earth elements are calculated using radial wavefunctions from the Hartree-Fock relativistic method in the Cowan program. Gaussian analytical expressions with four exponential terms are fitted to the values for rare earth elements and the fitted coefficients are tabulated. The tables can be used to interpret the form factor measurements for rare earth metals. Using the radial integrals of Ce 4f and 5d electrons, the experimental measurement of the magnetic form factor of CePd(3) is investigated. PMID:22893242

Kobayashi, Kohjiro; Nagao, Tatsuya; Ito, Masahisa

2012-07-26

142

A new convection-fractionation model for the evolution of the principal geochemical reservoirs of the Earth's mantle  

NASA Astrophysics Data System (ADS)

There are geochemical reservoirs (CC, DM, PM, EM1, EM2, HIMU) in the Earth's mantle and crust. They are distinguished by their isotopic and chemical abundance ratios and they arise from the combination of partial melting, segregation, ascent of the melt, differentiation of the melt, and lateral transport. The fractionation generates the chemical and isotopic diversity, while the solid-state convection works toward homogenization in particular in mantle areas with high gradient of creeping velocity perpendicular to the velocity vector. The thermal and chemical evolution of the Earth's mantle and crust has been modeled simultaneously by a fractionation mechanism plus 2D-FD Oberbeck-Boussinesq thermal convection. In contrast with the published model K1 [Walzer, U., Hendel, R., 1997a. Time-dependent thermal convection, mantle differentiation and continental-crust growth. Geophys. J. Int. 130, 303-325 geological interpretation: Walzer, U., Hendel, R., 1997b. Tectonic episodicity and convective feedback mechanisms. Phys. Earth Planet. Interiors 100, 167-188], layered convection is not an assumption but the mineral phase changes are introduced for 410 and 660 km depth using customary values of the Clapeyron slope, the density contrast, etc. So we have heat sources and sinks at 410 and 660 km, respectively, in addition to the usual Rayleigh number, Rq, for internal heating by radioactivity and bottom heating at the core-mantle boundary (CMB). The viscosity is a function of the temperature field and the pressure. Segregation takes place if the asthenospheric viscosity falls below a certain threshold. Oceanic plateaus, enriched in incompatible elements, develop leaving behind depleted parts of the mantle (DM). The resulting inhomogeneous heat-source distribution generates a first feedback mechanism. A growing continent is produced by accretion and further fractionation, consuming the older oceanic plateaus. The lateral movability of the growing continent causes a second feedback mechanism. The mentioned mechanisms generate acceptable distributions of the convective vigor and of the growth of juvenile continent material over the time axis. These distributions are stable for a moderate variation of the parameters only. The solutions of the system of differential equations show acceptable values for the distributions of the temperature, viscosity, heat flow, mantle-creep velocity and the continent's velocity. The following new result is insensitive to a strong variation of Rq: After an initially rather complex mixing process of the depleted parts and the pristine parts of the mantle, we arrive at a mainly depleted upper half of the mantle including the uppermost parts of the lower mantle and a predominantly pristine lower half of the mantle in the Phanerozoic at the latest. There is no sharp interface between the halves.

Walzer, U.; Hendel, R.

1999-04-01

143

Temperature dependence of magnetic EXAFS for rare earth elements  

Microsoft Academic Search

A systematic study of the x-ray magnetic circular dichroism at the L3 edge is presented for Gd and Tb single crystals in the extended energy range (MEXAFS). The investigation of the dichroic signal in this energy range is especially interesting for rare earth metals because the relative intensity of the magnetic EXAFS to the near edge signal (XMCD) is much

H. Wende; A. Scherz; C. Sorg; Z. Li; P. Poulopoulos; K. Baberschke; A. L. Ankudinov; J. J. Rehr; F. Wilhelm; N. Jaouen; A. Rogalev; D. L. Schlagel; T. A. Lograsso

2005-01-01

144

Magnetism of silicon doped with alkaline earth elements  

Microsoft Academic Search

It would be highly desirable to fashion spintronic materials based on silicon because of the vital importance of silicon in semiconductor technology. Since it is very difficult to experimentally dope transition metals into silicon, we explore the possibility of ferromagnetism in silicon doped with alkaline earth atoms using first-principle calculations. It is found that the energy needed for doping a

Bang-Gui Liu; Li-Jie Shi; Steven G. Louie

2005-01-01

145

Rare-earth elements in the Permian Phosphoria Formation: Paleo proxies of ocean geochemistry  

USGS Publications Warehouse

The geochemistry of deposition of the Meade Peak Member of the Phosphoria Formation (MPM) in southeast Idaho, USA, a world-class sedimentary phosphate deposit of Permian age that extends over 300,000 km2, is ascertained from its rare earth element (REE) composition. Ratios of REE:Al2O3 suggest two sources-seawater and terrigenous debris. The seawater-derived marine fraction identifies bottom water in the Phosphoria Sea as O2-depleted, denitrifying (suboxic) most of the time, and seldom sulfate-reducing (anoxic). This interpretation is supported by earlier research that showed progressively greater ratios in the marine sediment fraction of Cr:Ni>V:Ni???Mo:Ni, relative to their ratios in seawater; for which marine Cr, V, and Mo can have a dominantly O2-depleted bottom-water source and Ni a photic-zone, largely algal, source. The water chemistry was maintained by a balance between bacterial oxidation of organic matter settling through the water column, determined largely by primary productivity in the photic zone, and the flux of oxidants into the bottom water via advection of seawater from the open ocean. Samples strongly enriched in carbonate fluorapatite, the dominant REE host mineral, have variable Er/Sm, Tm/Sm, and Yb/Sm ratios. Their distribution may represent greater advection of seawater between the Phosphoria Sea and open ocean during deposition of two ore zones than a center waste and greater upwelling of nutrient-enriched water into the photic zone. However, the mean rate of deposition of marine Ni, a trace nutrient of algae, and PO43-, a limiting nutrient, indicate that primary productivity was probably high throughout the depositional history. An alternative interpretation of the variable enrichments of Er, Tm, and Yb, relative to Sm, is that they may reflect temporally variable carbonate alkalinity of open-ocean seawater in Permian time. A more strongly negative Ce anomaly for all phosphatic units than the Ce anomaly of modern pelletal phosphate is further indicative of an elevated O2 concentration in the Permo-Carboniferous open ocean, as proposed by others, in contrast to the depletion of O2 in the bottom water of the Phosphoria Sea itself. The oceanographic conditions under which the deposit accumulated were likely similar to conditions under which many sedimentary phosphate deposits have accumulated and to conditions under which many black shales that are commonly phosphate poor have accumulated. A shortcoming of several earlier studies of these deposits has resulted from a failure to examine the marine fraction of elements separate from the terrigenous fraction. ?? 2007 Elsevier Ltd. All rights reserved.

Piper, D. Z.; Perkins, R. B.; Rowe, H. D.

2007-01-01

146

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

147

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

Microsoft Academic Search

We present detailed experimental results on the partitioning of rare 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 for heterovalent substitution, crystal composition, and melt composition. We illustrate that the partition coefficients for Sm depend very strongly on the

Stefan Prowatke; Stephan Klemme

2006-01-01

148

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

149

The Criffell zoned pluton: correlated behaviour of rare earth element abundances with isotopic systems  

Microsoft Academic Search

Concentric zoning in the Criffell pluton takes the form of a discontinuous outer margin of metaluminous hornblende granodiorite and an inner core of increasingly peraluminous muscovite granite. Previous investigations using major and selected trace elements have shown the variation to consist of both smooth and abrupt trends. This study of 15 samples for the rare earth elements shows patterns which

W. Edryd Stephens; John E. Whitley; Matthew F. Thirlwall; Alex N. Halliday

1985-01-01

150

The igneous crystallization history of an ancient Martian meteorite from rare earth element microdistributions  

Microsoft Academic Search

Rare earth element (REE) and other selected trace and minor element concentrations were measured in individual grains of orthopyroxene, feldspathic glass (of plagioclase composition) and whitlockite of the ALH84001 martian meteorite. Unlike in other martian meteorites, phosphate is not the main REE carrier in ALH84001. The REE pattern of ALH84001 bulk rock is dependent on the modal abundances of three

Meenakshi Wadhwa; Ghislaine Crozaz

1998-01-01

151

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

152

Trace and Rare Earth Elements Geochemistry of Oshosun Sediments of Dahomey Basin, Southwestern Nigeria  

Microsoft Academic Search

Geochemical data of two borehole samples that penetrated Oshosun formation in Oja-Odan area located in the western part of the Dahomey basin of SW Nigeria were studied. A total of twenty-nine elements, comprising three major, twenty trace and six rare earth elements were considered with the objective of determining the distribution pattern, source rocks and the environment of deposition of

T. R. Ajayi; A. A. Oyawale; F. Y. Islander; O. I. Asubiojo; D. E. Klein; A. I. Adediran

2006-01-01

153

Rare earth element complexation by carbonate and oxalate ions  

NASA Astrophysics Data System (ADS)

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

Cantrell, Kirk J.; Byrne, Robert H.

1987-03-01

154

Rare-earth elements in heat-treatable steels  

SciTech Connect

Alloying functions of rare earth metals (REM) in iron and steel are discussed. REM have limited solid solubilities in iron, but they strongly tend to segregate to the grain boundaries. They effect phase transformation in steels and also the morphologies of the transformation products. REM have a significant influence on the mechanical properties of steels, particularly on those closely related to the properties of the grain boundaries.

Zhang, S.; Wu, C.

1986-01-01

155

Highly siderophile element constraints on accretion and differentiation of the Earth-Moon system.  

PubMed

A new combined rhenium-osmium- and platinum-group element data set for basalts from the Moon establishes that the basalts have uniformly low abundances of highly siderophile elements. The data set indicates a lunar mantle with long-term, chondritic, highly siderophile element ratios, but with absolute abundances that are over 20 times lower than those in Earth's mantle. The results are consistent with silicate-metal equilibrium during a giant impact and core formation in both bodies, followed by post-core-formation late accretion that replenished their mantles with highly siderophile elements. The lunar mantle experienced late accretion that was similar in composition to that of Earth but volumetrically less than (approximately 0.02% lunar mass) and terminated earlier than for Earth. PMID:17218521

Day, James M D; Pearson, D Graham; Taylor, Lawrence A

2007-01-12

156

Rare earth element behavior in the development of energy resources  

SciTech Connect

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

Laul, J.C.

1984-04-02

157

On the overabundance of light rare earth elements in terrestrial zircons and its implication for Earth's earliest magmatic differentiation  

Microsoft Academic Search

We present whole-rock and zircon rare earth element (REE) data from two early Archaean gneisses (3.81 Ga and 3.64 Ga) from the Itsaq gneiss complex, south-west Greenland. Both gneisses represent extremely rare examples of unaltered, fresh and relatively undeformed igneous rocks of such antiquity. Cathodoluminescence imaging of their zircons indicates a single crystallisation episode with no evidence for either later

Martin J. Whitehouse; Balz S. Kamber

2002-01-01

158

The formation of sulfate and elemental sulfur aerosols under varying laboratory conditions: implications for early earth.  

PubMed

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45?×?10(9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO(2)) by UV light with ??elemental sulfur (S(8)) and sulfuric acid (H(2)SO(4)) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO(2) 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 (H(2)) or methane (CH(4)), increased the formation of S(8). With UV photolysis, formation of S(8) aerosols is highly dependent on the initial SO(2) pressure; and S(8) is only formed at a 2% SO(2) mixing ratio and greater in the absence of a reductant, and at a 0.2% SO(2) mixing ratio and greater in the presence of 1000?ppmv CH(4). We also found that organosulfur compounds are formed from the photolysis of CH(4) and moderate amounts of SO(2). The implications for sulfur aerosols on early Earth are discussed. Key Words: S-MIF-Archean atmosphere-Early Earth-Sulfur aerosols. PMID:21087157

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

2010-10-01

159

Minor and trace element geochemistry of volcanic rocks dredged from the Galapagos spreading center: role of crystal fractionation and mantle heterogeneity.  

USGS Publications Warehouse

A wide range of rock types (abyssal tholeiite, Fe-Ti-rich basalt, andesite, and rhyodacite) were dredged from near 95oW and 85oW on the Galapagos spreading center. Computer modeling of major element compositions has shown that these rocks could be derived from common parental magmas by successive degrees of fractional crystallization. However, the P2O5/K2O ratio implies distinct mantle source compositions for the two areas. These source regions also have different rare earth element (REE) abundance patterns. The sequence of fractionated lavas differs for the two areas and indicates earlier fractionation of apatite and titanomagnetite in the lavas from 95oW. The mantle source regions for these two areas are interpreted to be depleted in incompatible (and volatile?) elements, although the source region beneath 95oW is less severely depleted in La and K. -Authors

Clague, D. A.; Frey, F. A.; Thompson, G.; Rindge, S.

1981-01-01

160

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

Microsoft Academic Search

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

Bernard J. Wood; Jonathan D. Blundy

1997-01-01

161

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

162

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

SciTech Connect

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

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

1993-02-01

163

Rare earth elements as indicators of different marine depositional environments in chert and shale  

NASA Astrophysics Data System (ADS)

Differences in rare earth element (REE) relative fractionations and total abundances in marine cherts and shales reflect the depositional location of the sediments. Based on cerium anomaly (Ce/Ce*) and total REE abundance (?REE) variations preserved in interbedded chert and shale sequences of the Franciscan assemblage, the Claremont Formation, and the Monterey Formation of coastal California, we can resolve three depositional regimes: spreading ridge proximal, ocean-basin floor, and continental margin. This resolution of depositional environment, previously unattainable in otherwise physically indistinct marine sedimentary rocks, provides a potentially powerful new tool for tectonic and stratigraphic reconstructions. Chert and shale deposited near the spreading ridge (within ˜400 km) under the influence of metalliferous activity are characterized by extremely low Ce anomalies (Ce/Ce* ˜0.29), those from an ocean-basin floor setting by well-developed yet less extreme Ce anomalies (Ce/Ce* ˜0.55), and those from continental margin regimes by no or slight anomalies (Ce/Ce* ˜0.90 to 1.30). ?REE in chert and shale are extremely low in regimes greatly influenced by continental input, owing to the high sedimentation rate, which minimizes exposure time to seawater and, thus, the adsorption of REE. Preliminary results indicate that the effect of diagenesis does not mask the primary REE depositional signature.

Murray, Richard W.; Buchholtz Ten Brink, Marilyn R.; Jones, David L.; Gerlach, David C.; Russ, G. Price, III

1990-03-01

164

Rare earth elements as indicators of different marine depositional environments in chert and shale  

SciTech Connect

Differences in rare earth element (REE) relative fractionations and total abundances in marine cherts and shales reflect the depositional location of the sediments. Based on cerium anomaly (Ce/Ce{asterisk}) and total REE abundance ({Sigma}REE) variations preserved in interbedded chert and shale sequences of the Franciscan assemblage, the Claremont Formation, and the Monterey Formation of coastal California, we can resolve three depositional regimes: spreading ridge proximal, ocean-basin floor, and continental margin. This resolution of depositional environment, previously unattainable in otherwise physically indistinct marine sedimentary rocks, provides a potentially powerful new tool for tectonic and stratigraphic reconstructions. Chert and shale deposited near the spreading ridge (within {approximately} 400 km) under the influence of metalliferous activity are characterized by extremely low Ce anomalies (Ce/Ce{asterisk} {approximately} 0.29), those from an ocean-basin floor setting by well-developed yet less extreme Ce anomalies (Ce/Ce{asterisk} {approximately} 0.55), and those from continental margin regimes by no or slight anomalies (Ce/Ce{asterisk} {approximately} 0.90 to 1.30). {Sigma}REE in chert and shale are extremely low in regimes greatly influenced by continental input, owing to the high sedimentation rats, which minimizes exposure time to seawater and, thus, the adsorption of REE. Preliminary results indicate that the effect of diagenesis does not mask the primary REE depositional signature.

Murray, R.W.; Jones, D.L. (Univ. of California, Berkeley (USA)); Bruchholtz ten Brink, M.R.; Gerlach, D.C.; Russ, G.P. III (Lawrence Livermore National Laboratory, CA (USA))

1990-03-01

165

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

166

Additional effects of rare earth elements on formation and properties of some transition metal pyrophosphates  

Microsoft Academic Search

Transition metal phosphates have been used as inorganic pigments. By the addition of rare earth elements, new functional materials are expected to form. In this work, rare earth oxides (Y2O3, La2O3, CeO2, and Nd2O3) were added in the formation systems of copper, manganese, and cobalt pyrophosphates prepared from ammonium dihydrogenphosphate and the transition metal carbonate. The thermal behaviors of the

Hiroaki Onoda; Kazuo Kojima; Hiroyuki Nariai

2006-01-01

167

Geochemistry of the rare-earth elements in hypersaline and dilute acidic natural terrestrial waters: Complexation behavior and middle rare-earth element enrichments  

Microsoft Academic Search

Rare-earth element (REE) speciation was modelled in acid (2.9 ? pH ? 3.5), hypersaline groundwaters from Australia and from the Palo Duro Basin in Texas, USA, using a combined specific ion interaction (Pitzer model) and ion pairing model. The free metal ion species (i.e. Ln3+) is the dominant form of dissolved REEs in these systems, accounting for 40–70% of the

Kevin H. Johannesson; W. Berry Lyons; Mary A. Yelken; Henri E. Gaudette; Klaus J. Stetzenbach

1996-01-01

168

The aqueous geochemistry of the rare earth elements. Part XIV. The solubility of rare earth element phosphates from 23 to 150 °C  

Microsoft Academic Search

Rare earth element (REE) phosphates such as monazite and xenotime are important as ore minerals, potential hosts of radioactive waste, and target phases for isotopic dating. However, there are still insufficient thermodynamic data with which to model dissolution and precipitation of these phases in crustal fluids quantitatively. Therefore, the solubilities of end-member La(III)-, Nd(III)-, Sm(III)-, and Y(III)- phosphates were determined

Ziya S. Cetiner; Scott A. Wood; Christopher H. Gammons

2005-01-01

169

Comparative study of yttrium and rare-earth element behaviours in fluorine-rich hydrothermal fluids  

NASA Astrophysics Data System (ADS)

The mineral ‘fluorite’ is utilized as a probe to investigate the behaviour of the pseudolanthanide yttrium with respect to the lanthanides (rare-earth elements, REE) in fluorine-rich hydrothermal solutions. Hydrothermal vein fluorites are characterized by the close association of Y and REE, but in contrast to igneous and clastic rocks they show variable and non-chondritic Y/Ho ratios of up to 200. This suggests that Y and Ho, although similar in charge and size, may be fractionated in fluorine-rich medium-temperature aqueous fluids. In such solutions Y acts as a pseudolanthanide heavier than Lu. Y/Ho ratios of hydrothermal siderites are slightly below those of chondrites, suggesting that in (bi)carbonate-rich siderite-precipitating solutions Y may act as a Sm-like light pseudolanthanide. This indicates that Y-Ho fractionation is not a source-related phenomenon but depends on fluid composition. Based on these results it is strongly recommended that discussions of normalized REE patterns in general should be extended to normalized Rare-Earth-and-Yttrium (REY) patterns (Y inserted between Dy and Ho), because the slightly variable behaviour of the pseudolanthanide yttrium with respect to the REE may provide additional geochemical information. Available thermodynamic data suggest a negative correlation between Y/Ho and La/Ho during migration of a fluorite-precipitating hydrothermal solution. Cogenetic fluorites, therefore, should display either similar Y/Ho and similar La/Ho ratios, or a negative correlation between these ratios. This criterion may help to choose samples suitable for Sm-Nd isotopic studies prior to isotope analysis. However, in cogenetic hydrothermal vein fluorites the range of Y/Ho ratios is often almost negligible compared to the range of La/Ho ratios. This may be explained by modification of REE distributions by post-precipitation processes involving (partial) loss of a separate LREE-enriched phase. The presence of variable amounts of such an accessory phase in most fluorite samples is revealed by experiments employing stepwise incomplete fluorite decomposition. Fluorites derived from and deposited near to igneous rocks apparently display chondritic Y/Ho ratios close to those of their igneous source-rocks. However, a positive YSN anomaly is likely to develop as the distance between sites of REY mobilization and deposition increases.

Bau, Michael; Dulski, Peter

1995-03-01

170

The igneous crystallization history of an ancient Martian meteorite from rare earth element microdistributions  

NASA Astrophysics Data System (ADS)

Rare earth element (REE) and other selected trace and minor element concentrations were measured in individual grains of orthopyroxene, feldspathic glass (of plagioclase composition) and whitlockite of the ALH84001 martian meteorite. Unlike in other martian meteorites, phosphate is not the main REE carrier in ALH84001. The REE pattern of ALH84001 bulk rock is dependent on the modal abundances of three REE-bearing phases, i.e., orthopyroxene (which contains most of the HREEs), feldspathic glass (which dominates the Eu abundances) and whitlockite (which contains the majority of the LREEs). Variations in the REE abundances previously observed in different splits of ALH84001 can easily be explained in terms of small variations in the modal abundances of these three minerals, without the need to invoke extensive redistribution of LREEs. At least some orthopyroxenes (i.e., those away from contacts with feldspathic glass) in ALH84001 appear to have preserved their original REE zonation from igneous fractionation. Estimate of the ALH84001 parent magma composition from that of the unaltered orthopyroxene `core' (i.e., zoned orthopyroxene with the lowest REE abundances) indicates that it is LREE-depleted. This implies that the martian mantle was already partly depleted within ~100 Ma of solar system formation, consistent with rapid accretion and differentiation of Mars. Although equilibration and exchange of REEs between phases (in particular, transport of LREEs into the interstitial phases, feldspathic glass and whitlockite) cannot be ruled out, our data suggest that the LREE-enrichment in melts `in equilibrium' with these interstitial phases is most likely the result of late-stage infiltration of the cumulate pile by a LREE-enriched melt.

Wadhwa, Meenakshi; Crozaz, Ghislaine

1998-07-01

171

Extraction of impurities of rare-earth elements from uranium dioxide using bromine trifluoride for their preconcentration and analytical determination  

Microsoft Academic Search

The behavior of impurities of rare-earth elements in the fluorination of UO2 with bromine trifluoride is studied by the radioactive tracer method using152Eu radionuclide. It is demonstrated that uranium is completely removed as hexafluoride, whereas impurities of rare-earth elements\\u000a quantitatively remain in the crucible because of the nonvolatility of their fluorides. Based on this fact, the concentrations\\u000a of rare-earth elements

V. N. Mit’kin; B. M. Shavinskii; A. I. Kamelin

2000-01-01

172

On the overabundance of light rare earth elements in terrestrial zircons and its implication for Earth’s earliest magmatic differentiation  

Microsoft Academic Search

We present whole-rock and zircon rare earth element (REE) data from two early Archaean gneisses (3.81 Ga and 3.64 Ga) from the Itsaq gneiss complex, south-west Greenland. Both gneisses represent extremely rare examples of unaltered, fresh and relatively undeformed igneous rocks of such antiquity. Cathodoluminescence imaging of their zircons indicates a single crystallisation episode with no evidence for either later

Martin J Whitehouse; Balz S Kamber

2002-01-01

173

Method and particle mixture for making rare earth element, iron and boron permanent sintered magnets  

SciTech Connect

This patent describes a method for producing sintered permanent magnets of a permanent magnet alloy comprising a rare earth element, iron and boron. It comprises providing a permanent magnet, rare earth element, iron and boron alloy material dross alloy and up to 6% scrap alloy; dross alloy and virgin alloy; and dross alloy and virgin alloy and greater than 0 to 80% scrap alloy, sequentially hydrating the material in a hydrogen atmosphere to hydride and decreptitate the material to form particles therefrom, reducing the size of the particles, compacting the particles and dehydrating and sintering the particles to produce a substantially fully dense article for use as a permanent magnet.

Kim, A.S.

1992-02-25

174

Accurate Determination of Rare Earth Elements in USGS, NIST SRM, and MPI-DING Glasses by Excimer LA-ICP-MS at High Spatial Resolution  

Microsoft Academic Search

The effect of central gas flow rate (carrier gas and makeup gas) on signal intensities, ThO\\/Th, Th\\/U, memory effect, and interface pressures were investigated in this work. Detailed examination of the changing trend of fractionation index with different crater diameters from 8 µm to 60 µm reveals that rare earth elements (REEs) can also be classified into three groups: (1) La, Pr,

Zhaochu Hu; Shan Gao; Yongsheng Liu; Haihong Chen; Shenghong Hu

2008-01-01

175

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

176

Mass-Independent Fractionation of Oxygen Isotope in Earth Wind: First Principle Calculations for Photodissociation  

NASA Astrophysics Data System (ADS)

Mass-independently fractionated oxygen isotope were reported on metal particles extracted from Apollo lunar soils [1, 2], but these origins are still unknown. Since the substantial fraction of Earth-escaping O+ flux (Earth Wind, EW hereafter), comparable to the amount of the anomalous oxygen implanted on the metal particles, could reach the lunar surface [3], Ozima et al. [4] suggested that EW may be responsible to the anomalous oxygen. The purpose is to test this EW hypothesiss, we study oxygen isotopic ratios of O+ at the upper atmosphere. From quantum chemical calculations of photo-dissociation of O2, we show the results in mass-independent isotopic fractionation of oxygen, thereby in conformity with the EW hypothesis. First principles reaction dynamics simulations were performed to compute the photolysis rate for the B3?u- ? X3?g- electronic transition, for Schumann-Runge band. With the assumption of the Born-Oppenheimer approximation, we performed the wave-packet dynamics for the nuclei-motion in the potential energy curves determined by the first step calculation. Quantum chemical program package [5] was used for the first step calculation, and the quantum dynamics was carried out by our own program package. Assuming the quantum yield of the corresponding photolysis is unity, the photo-absorption cross section can be correlated with the photolysis rate. Therefore, following the time dependent approach, the autocorrelation function (A(t) = ) was numerically computed by the second step calculation. Finally, the theoretical spectrum as a function of wavelength of excitation light was estimated by the Fourier transform of the autocorrelation function A(t) [6]. Calculated absorption cross sections for C16O showed similar wavelength dependence with experiment [7], although the absolute magnitude was yet to be calibrated for a quantitative comparison. Assuming Boltzmann distribution at 1200 K, we estimated enrichment factors defined as ??(?)/?16(?) - 1 (i = 17, 18) using the above calculated cross sections. Assuming SMOW for the initial oxygen isotopic composition, the isotopic ratios of O atom dissociated from O2 are ?17O = 5.62‰, ?18O = 3.53‰, ?17O = 3.8‰, suggesting large mass-independent isotopic fractionation in photo-dissociation of CiO. Numerical values of isotopic fractionation (e.g. ?17O) can be obtained by solving photochemical reaction equations in the thermosphere conditions (>100 km) with the above estimated dissociation rates, where effective O+ pickup is likely to take place. We are currently working on the latter problem with hopes that this would test the EW hypothesis. References: [1] Ireland et al., 2006, Nature, 440:776. [2] Hashizume & Chaussidon, 2009, GCA, 73:3038. [3] Seki et al., 2001, Science, 291:1939. [4] Ozima et al., 2008, PNAS, 105:17654. [5] Werner & Knowles, http://www.molpro.net. [6] Heller, 1978, J. Chem. Phys., 68:2066. [7] Ackermann et al., 1970, Planet. Space Sci., 18:1639.

Yamada, A.; Nanbu, S.; Kasai, Y.; Ozima, M.

2009-12-01

177

Petrogenesis of Archaean ultrabasic and basic volcanics: Evidence from rare earth elements  

Microsoft Academic Search

Rare earth element (REE) and major element data are presented on 44 Archaean samples which include spinifex textured ultramagnesian lavas (STPK) spinifex textured basalts (STB) and low MgO tholeiites. The samples come from the Yilgarn and Pilbara Blocks (W. Australia), Barberton (South Africa), Belingwe and Que Que (Rhodesia), Abitibi (Canada) and the 3.7 b.y. Isua Belt of Western Greenland. In

Shen-Su Sun; Robert W. Nesbitt

1978-01-01

178

Controls on the distribution of rare earth elements in shallow groundwaters  

Microsoft Academic Search

Shallow groundwater samples (<0.22?m) collected from a small catchment in Western France (Petit Hermitage catchment) were analyzed for their rare earth elements (REE), dissolved organic carbon (DOC) and trace-element (Fe, Mn, Th and U) contents, with the aim to investigate the controlling factors of REE signatures. Two spatially distinct water types are recognized in this catchment based on changes of

Gérard Gruau; Aline Dia; Gwenaelle Olivié-Lauquet; Mélanie Davranche; Gilles Pinay

2004-01-01

179

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

Microsoft Academic Search

Bamsar, Revesht and Nezam-Abad tungsten deposits are located southwest of Shazand in central Iran. Rare Earth Element (REE) and other trace elements in samples of scheelite (CaWO4) from these deposits have been determined by Neutron Activation Analysis in order to constrain the composition and sources of the mineralizing fluids. Paleozoic and Triassic volcano-sedimentary rocks and upper Triassic-Jurassic detrital-chemical and volcanic

M. Ghaderi

2001-01-01

180

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

Microsoft Academic Search

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

Glenn A. Gaetani; Timothy L. Grove

1995-01-01

181

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

182

Chemical Exchange Between the Core and the Convecting Mantle of the Earth: Evidence from Highly Siderophile Elements (HSE)  

Microsoft Academic Search

Core formation is a major physical and chemical event in the evolution of a differentiated planet. The core is the dominant repository of HSE in the Earth. Element ratios of HSE in peridotites provide insights into the accretion processes of the Earth and the effect of core formation. Depletion of HSE in the Earth's mantle results from core formation. Refractory

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

1995-01-01

183

SEPARATION OF RARE EARTH ELEMENTS BY CONTINUOUS ELECTROPHORESIS. SEPARATION BY CITRIC ACID  

Microsoft Academic Search

The effects of complexing agent concentrations, solution pH, and ; concentration of rare-earth elements on the mobility of La, Ce, Pm, Eu, and Y ; ions were investigated. The experiments used radioactive indicators and citric ; acid as complexing agent in separation of La-Ce-Y-Eu;

V. P. Shvedov; A. V. Stepnov

1959-01-01

184

Cerium redox cycles and rare earth elements in the Sargasso Sea  

Microsoft Academic Search

Two profiles of the rare earth elements (REEs) are reported for the upper water column of the Sargasso Sea. The trivalent-only REEs have remarkably constant concentrations in the upper 500m of an April 1989 profile and in the upper 200m of a May 1989 profile. In contrast, Ce concentrations decrease smoothly with increasing depth. In April 1989 Ce decreases from

E. R. Sholkovitz; D. L. Schneider

1991-01-01

185

Rare earth element mobility in vesicular lava during low-grade metamorphism  

Microsoft Academic Search

A geochemical comparison of basaltic relicts and spilitic domains from two burial metamorphosed flows in central Chile, of similar original composition and rich and poor in amygdules, respectively, demonstrates a relationship between initial vesicularity and rare earth element (REE) mobility. During spilitization the REE were partly leached from permeable parts of the flows and precipitated in voids, now amygdules and

Jan Olov Nyström

1984-01-01

186

Rare earth element distributions among coexisting granulite facies minerals, Scourian complex, NW Scotland  

Microsoft Academic Search

The major rock-forming mineral phases (pyroxenes, plagioclase, garnet, hornblende) of a suite of granulite-facies gneisses from the Scourian complex, NW Scotland, have been analyzed for their rare earth element (REE) content. Although host rock compositions range from felsic to ultramafic, REE abundances and patterns for each mineral group show only limited variation. The REEs exhibit regular and consistent distribution patterns

C. Pride; G. K. Muecke

1981-01-01

187

Mobility of rare-earth elements and copper during shear-zone-related retrograde metamorphism  

Microsoft Academic Search

In Mid Proterozoic crystalline rocks of the Mount Isa Inlier, around Cloncurry, Australia, 2000 km2 of alteration and brecciation are the product of high-temperature (> 450 °C) concentrated saline solution activity. During retrogression, this fluid was locally responsible for mobility of V, Y, Nb and light rare-earth elements (15 × enrichment). Copper and S were leached during alteration and this

Geoffrey de Jong; Jackie Rotherham; G. Neil Phillips; Patrick J. Williams

1997-01-01

188

The geochemistry of rare earth elements in the metamorphic rocks of the Kola series  

Microsoft Academic Search

The effect of rare earth element redistribution in the processes of sodium and potassium metasomatism of the metamorphic rocks of the Archean age plagiogranitic sequences of the Kola series are examined with reference to the results of neutron activation and X-ray fluorescence analyses of 43 samples. It is found that as a result of potassium metasomatism, the total concentration of

V. D. Nartikoev; M. Z. Abdrakhimov; N. E. Galdin; A. V. Gurevich

1982-01-01

189

Microdistributions and petrogenetic implications of rare earth elements in polymict ureilites  

Microsoft Academic Search

Polymict ureilites contain various mineral and lithic clasts not observed in monomict ureilites, including plagioclase, enstatite, feldspathic melt clasts and dark inclusions. This paper investigates the microdistributions and petrogenetic implications of rare earth elements (REEs) in three polymict ureilites (Elephant Moraine (EET) 83309, EET 87720 and North Haig), focusing particularly on the mineral and lithic clasts not found in monomict

Yunbin Guan; Ghislaine Crozaz

2001-01-01

190

Improved Ion-Exchange Separation of Rare-Earth Elements for Spectrographic Analysis.  

National Technical Information Service (NTIS)

Rare-earth elements are separated from scandium and base metals by adsorption onto anion resin BIORAD AG1-X8 in the nitrate form from a mixture of 5% 7 M nitric acid and 95% methanol. The yttrium subgroup is eluted with a mixture of 45% 7 M nitric acid an...

E. A. Jones

1978-01-01

191

Far-Zone Field of a Monopole Element on a Disk Ground Plane above Flat Earth.  

National Technical Information Service (NTIS)

Richmond's moment-method analysis for the current distribution and input impedance of a monopole element on a disk ground plane above flat Earth is used to obtain the far-zone field in the free-space region. Numerical results for directivity and radiation...

M. M. Weiner

1992-01-01

192

Input Impedance and Gain of Monopole Elements with Disk Ground Planes on Flat Earth.  

National Technical Information Service (NTIS)

This paper extends previously reported results for a quarterwave monopole element on a disk ground plane in free space to the case where the disk ground plane rests on flat earth. Numerical results are obtained by utilizing Richmond's method of moments co...

M. M. Weiner

1990-01-01

193

Black Body Temperature in Terms of Earth's Orbital Elements and the Milankovitch Precession Index  

Microsoft Academic Search

The temperature T of a black or gray body orbiting the Sun can be expressed in terms of spherical harmonics in latitude and longitude, its Keplerian orbital elements, and a variable describing rotation about its axis. Assuming that the Earth is a gray body, the resulting equation for T exhibits previously unrecognized odd-degree zonal terms dubbed \\

D. P. Rubincam

2002-01-01

194

Origin of Planetary Cores: Evidence for Mars-Earth Similarity in Distribution of Highly Siderophile Elements  

Microsoft Academic Search

New bulk compositional data for six martian meteorites, including highly siderophile elements Ni, Re, Os, Ir, and Au [ I ], are utilized along with literature data for comparison with the siderophile systematics of igneous rocks from Earth, the Moon, and the HED asteroid. Queen Alexandra Range 94201 and EET 79001-B are both depleted in the \\

P. H. Warren; G. W. Kallemeyn; F. T. Kyte

1998-01-01

195

Rare earth element partitioning between clinopyroxene and silicate liquid at moderate to high pressure  

Microsoft Academic Search

Experimental determination of over seventy sets of clinopyroxene\\/silicate liquid (glass) partitition coefficients (D) for four rare earth elements (REE — La, Sm, Ho, Lu) in a range of REE-enriched natural rock compositions (basalt, basaltic andesite, andesite and rhyodacite) demonstrate a convex upward pattern, favouring the heavy REE (Ho, Lu) and markedly discriminating against the light REE (La). These patterns are

T. H. Green; N. J. Pearson

1985-01-01

196

Rare earth elements in soil and in soil-grown plants  

Microsoft Academic Search

Concentrations of the rare earth elements (REEs) La, Ce, Nd, Sm, Eu, Gd, Tb, Yb and Lu were determined in leaves of 6 plant species (Norway spruce, silver fir, maple, ivy, blackberry, and wood fern), and in pertinent soils and soil extracts, also taken from the same site. The distribution of the individual REEs in plants showed little or no

A. Wyttenbach; V. Furrer; P. Schleppi; L. Tobler

1998-01-01

197

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

198

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

Microsoft Academic Search

A method of analysis of geological materials for the determination of the rare-earth elements using the inductively coupled plasma mass spectrometric technique (ICP-MS) has been developed. Instrumental parameters and factors affecting analytical results have been first studied and then optimized. Samples are analyzed directly following an acid digestion, without the need for separation or preconcentration with limits of detection of

Frederick E. Lichte; Allen L. Meier; James G. Crock

1987-01-01

199

Island weathering: river sources of rare earth elements to the Western Pacific Ocean  

Microsoft Academic Search

This paper focuses on two of the largest rivers and estuaries of Papua New Guinea (PNG), the Fly and Sepik and explores the degree to which river input and estuarine reactions affect the rare earth element (REE) composition of surface sea water in the western tropical Pacific Ocean. The dissolved phases of the Fly and Sepik River waters have striking

E. r. Sholkovitz; H. Elderfield; R. Szymczak; K. Casey

1999-01-01

200

The partitioning of rare earth elements between garnet and liquid at high pressures: Preliminary experiments  

Microsoft Academic Search

Preliminary experiments were made to determine the partition coefficients of rare earth elements between garnet and liquid at 30 kb and 1275°C in the system diopside (30 wt%) -pyrope(70%) -water. REE were added to the system by titration at concentration levels in the range of natural basalts. The phases were separated by differential dissolution technique (DDT) and analized for REE

N. Shimizu; I. Kushiro

1975-01-01

201

Reversibility of exchange of alkaline-earth elements on hydrated tin and titanium oxides  

Microsoft Academic Search

The sorption of alkaline-earth elements by hydrated tin and titanium oxides was investigated. It was found that the reversibility of exchange, due to the stability of the sorption complex and to the conditions of competition in the system, is determined by a combination of the characteristics of the sorbate and the sorbent. The most important of these characteristics are their

T. N. Perekhozeva; L. M. Sharygin; S. M. Vovk

1988-01-01

202

Enthalpies of dissolution of elements in liquid tin: II. Transition, alkali and alkaline-earth metals  

Microsoft Academic Search

In the framework of a general compilation devoted to the enthalpies of dissolution of elements in liquid tin, the data concerning the partial enthalpies at infinite dilution of transition metals, alkali metals and alkaline–earth metals in tin have been collected from literature and selected data are given. When the number of data was large enough, they were fitted against temperature

Abeer Yassin; Robert Castanet

2001-01-01

203

The Behavior of Some Lines of Rare-Earth Elements on the Solar Disk.  

National Technical Information Service (NTIS)

The behavior of equivalent widths and half-widths of some lines of rare earth elements on the solar disk was investigated: the center-limb effect, the transition from absorption to emission and the emission in active regions. The variation of the equivale...

N. N. Stefanovich

1965-01-01

204

Modeling 3D Wave Propagation in Global Earth Models Using a Spectral\\/Mortar Element Method  

Microsoft Academic Search

The Spectral Element Method (SEM) has been shown in recent years to provide an efficient, accurate solution to wave propagation in the Earth at both regional and global scales. Based on a high order polynomial approximation of the weak form of the wave equation, the SEM naturally takes into account the free surface condition (which is crucial for surface wave

E. O. Chaljub; J. Vilotte

2001-01-01

205

Seasonality of dissolved rare earth elements in the lower Mississippi River  

Microsoft Academic Search

Dissolved rare earth element (REE) concentrations were determined in a 27-month time series of the lower Mississippi River. Overall, the results agree with limited previous investigations; that is, the river shows enrichment of heavy REEs relative to light REEs and also has a significant Ce anomaly. However, the previous investigations relied on only single samples from the river. This seasonal

Alan M. Shiller

2002-01-01

206

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...

207

Effect of paleosol formation on rare earth element signatures in fossil bone  

Microsoft Academic Search

The rare earth element (REE) content of fossil bones was analyzed and compared with the degree of ancient pedogenic development and depositional environments from several locations in the Orellan Scenic Member of the Oligocene Brule Formation in Badlands National Park, South Dakota. Paleosols ranged from weakly developed Entisols to more strongly developed Inceptisols, all typical of fluvial environments and possible

Christine A. Metzger; Dennis O. Terry Jr.; David E. Grandstaff

2004-01-01

208

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

National Technical Information Service (NTIS)

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

S. A. Wood

2001-01-01

209

Prediction of trajectories in the Earth's gravitational field with axial symmetry using KS uniform regular elements  

Microsoft Academic Search

In this paper, a motion prediction algorithm based on the KS regular elements is developed for the motion in the Earth's gravitational field with axial symmetry. The algorithm is of recursive nature and general in the sense that it could be applied for any conic motion whatever the number of zonal harmonic coefficientsN = 2 may be. Applications of the

Amr A. Sharaf

1993-01-01

210

PRESENCE OF RARE-EARTH ELEMENTS IN BLACK FERROMANGANESE COATINGS FROM VÂNTULUI CAVE (ROMANIA)  

Microsoft Academic Search

This study examines the rare-earth elements (REEs) found in ferromanganese coatings covering both sandy alluvium and submerged boulders in an underground stream from Vântului Cave, Romania. The black ferromanganese sediments are mainly composed of birnessite and other poorly-crystallized man- ganese oxide and hydroxides (pyrolusite, romanechite, todorokite, rhodochrosite) as well as goethite and kaolinite. Scanning electron microscope and EDX analyses performed

BOGDAN P. O NAC; ROLF B. PEDERSEN; MAGNE TYSSELAND

211

Analysis of Impurities in Rare Earth and Transplutonium Elements by Direct Spectral Method.  

National Technical Information Service (NTIS)

A direct spectral analysis method is developed for a quantitative determination of the main impurities (Ca, Fe, Si, Mg, Mn, Cr, Ni, Al, Pb, B, Be, La) in transplutonium and rare earth elements. The method permits the determination of 12 main impurities si...

G. V. Shishalova T. A. Nazarenko

1980-01-01

212

Rare earth elements of the Altar Desert dune and coastal sands, Northwestern Mexico  

Microsoft Academic Search

Twenty-one surficial sand samples from the Altar Desert coastal and desert dune systems were analysed for rare earth elements (REE) content. This was done to observe the provenance signatures for four strategic dune localities near the Colorado River Delta, the El Pinacate dune fields, and the beaches of the north of the Gulf of California in the state of Sonora,

Juan José Kasper-Zubillaga; Beatriz Acevedo-Vargas; Ofelia Morton Bermea; Glicinia Ortiz Zamora

2008-01-01

213

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

SciTech Connect

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

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

1985-04-20

214

Fractions and background concentrations of potentially toxic elements in Hungarian surface soils.  

PubMed

This work established background concentrations for the pseudo total (HNO(3) + H(2)O(2)-soluble), mobilisable (NH(4)-acetate + EDTA-soluble) and mobile (1 M NH(4)NO(3)-soluble) element fractions of Hungarian surface soils that can be used as reference values for the soil quality standards. The 193 soils investigated were taken from the Hungarian Soil Information and Monitoring System. The background values for Al, As, B, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr and Zn were given as a range covering 95% of the variance of the representative samples. The differences between observed element concentrations and the calculated background values indicated anthropogenic or pedogenic impact in each fraction. The comparison of the calculated background values with the Hungarian quality standards and the contamination limit values of other countries showed that the limit values of a certain region or country are not suitable for other areas. Generally, Mn and Al had the highest, while Cd had the lowest concentration in each fraction. Cr and Al were the least and Sr was the most mobile element. The principal component analysis indicated different geochemical and physico-chemical behaviour of the elements in the fractions; the pseudo total fraction was influenced more by the geological behaviour, while mobilisable and mobile fraction explained a much higher proportion of the total variance of soil physico-chemical properties than soil geochemical properties. The Cd-Ni and Co-Mn element pairs were always in the same principal component in each fractions indicating similar geogenic origin and showing that their solubility changes are similar in function of soil properties. PMID:22350444

Rékási, Márk; Filep, Tibor

2012-02-21

215

Oceanic crustal thickness from seismic measurements and rare earth element inversions  

SciTech Connect

Seismic refraction results show that the igneous section of oceanic crust averages 7.1 [plus minus] 0.8 km thick away from anomalous regions such as fracture zones and hot-spots, with extremal bounds of 5.0-8.5 km. Rare earth element inversions of the melt distribution in the mantle source region suggest that sufficient melt is generated under normal oceanic spreading centers to produce an 8.3 [plus minus] 1.5 km thick igneous crust. The difference between the thickness estimates from seismics and from rare earth element inversions is not significant given the uncertainties in the mantle source composition. The inferred igneous thickness increases to 10.3 [plus minus] 1.7 km (seismic measurements) and 10.7 [plus minus] 1.6 km (rare earth element inversions) where spreading centers intersect the regions of hotter than normal mantle surrounding mantle plumes. This is consistent with melt generation by decompression of the hotter mantle as it rises beneath spreading centers. Maximum inferred melt volumes are found on aseismic ridges directly above the central rising cores of mantle plumes, and average 20 [plus minus] 1 and 18 [plus minus] 1 km for seismic profiles and rare earth element inversions respectively. Both seismic measurements and rare earth element inversions show evidence for variable local crustal thinning beneath fracture zones, though some basalts recovered from fracture zones are indistinguishable geochemically from those generated on normal ridge segments away from fracture zones. The authors attribute the decreased mantle melting on very slow-spreading ridges to the conductive heat loss that enables the mantle to cool as it rises beneath the rift.

White, R.S.; McKenzie, D.; O'Nions, R.K. (Cambridge Univ. (United Kingdom))

1992-12-10

216

Rare earths and other trace elements in iron-manganese concretions from a catenary sequence of yellow-grey earth soils, New Zealand  

Microsoft Academic Search

Analyses of samples of iron-manganese concretions and their surrounding soil materials, from a catenary sequence of four yellowgrey earth soils (two Fragiaquepts and two Fragiochrepts) near Allanton, have been carried out using spark source mass spectrometry. Data are presented for 12 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) and 5 others

P. C. Rankin; C. W. Childs

1987-01-01

217

Uncertainty propagation through correction methodology for the determination of rare earth elements by quadrupole based inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Determination of rare earth elements by quadrupole based inductively coupled plasma mass spectrometry (ICP-QMS) shows several spectroscopic overlaps from M+, MO+ and MOH+ ions. Especially, the spectroscopic interferences are observed from the atomic and molecular species of lighter rare earth elements including Ba during the determination of Eu, Gd and Tb. Mathematical correction methods, knowing the at.% abundances of different

Narendra M. Raut; Li-Shing Huang; King-Chuen Lin; Suresh K. Aggarwal

2005-01-01

218

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

Microsoft Academic Search

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

Weiwei WAN; Jianmin HAN; Weijing LI; Jinhua WANG

2006-01-01

219

Evolution of the lithosphere beneath Oahu, Hawaii: rare earth element abundances in mantle xenoliths  

NASA Astrophysics Data System (ADS)

Rare earth element contents of clinopyroxenes in Hawaiian mantle xenoliths from Oahu were determined with an ion microprobe. The analyzed xenoliths are from four vents of the alkali Honolulu Volcanics (HV). Three (Kaau, Pali and Kalihi—KPK) are located close to the caldera of the extinct Koolau shield volcano, and the fourth, Salt Lake Crater (SLC), is on the periphery of the shield volcano. Systematic differences exist in REE contents between clinopyroxenes of the KPK and SLC xenoliths: (1) KPK pyroxenes are typically zoned in REE contents whereas SLC pyroxenes are homogeneous, (2) the LREE-depleted (chondrite-normalized) patterns that characterize many of the KPK xenoliths are not found in SLC xenoliths, and (3) the convex-upward REE patterns that are characteristic of SLC xenoliths are not found in KPK xenoliths. Relative to abyssal peridotites, the LREE-depleted Hawaiian lherzolite pyroxenes (interpreted to be residual oceanic lithosphere) have higher contents of REE, Na 2O, TiO 2 and FeO, and more modal clinopyroxene. These LREE-depleted Hawaiian xenoliths represent deeper, less-depleted parts of the melting column, whereas the abyssal peridotites represent the uppermost, more strongly depleted part of the mantle. The spoon-shaped, LREE-enriched and convex-upward REE patterns in the xenoliths have resulted from metasomatic enrichment of the lithosphere caused by reaction with magmas that formed the Honolulu Volcanics. A model for the evolution of the oceanic lithosphere is presented in which fractures were the main mode of transport of the Honolulu Volcanics. Metasomatic enrichment resulted from interaction between percolating Honolulu Volcanics magmas and wallrock. The differences between SLC and KPK xenoliths are attributed to chromatographic fractionation effects: SLC xenoliths are postulated to have come from a greater depth where they equilibrated to a larger extent with the percolating magmas than the KPK rocks.

Sen, Gautam; Frey, Frederick A.; Shimizu, Nobumichi; Leeman, William P.

1993-08-01

220

Rare-Earth-Element and Isotopic Evidence for the Genesis of the Bajiazi Stratabound Sulfide Ore Bodies of Northeast China  

Microsoft Academic Search

This study examines the rare-earth-elemenl and isotopic geochemistry of sulfide ores and associated rocks in the Bajiazi sulfide deposits of northeastern China. The distribution and concentration of rare earth elements (REE) in sulfide ores and associated rocks from the Bajiazi deposits have been determined by inductively coupled plasma spectroscopy (ICP) methods. Birdwing-shaped rare-earth-element profiles are only observed in granitic rocks

Baohong Hou; Dong Pu Zhao

1999-01-01

221

Elements in size-fractionated bottom sediments of the Elbe River in its Czech part  

Microsoft Academic Search

The concentrations of 45 elements, and the content of organic substances, amorphous inorganic substances and minerals were determined in 26 samples of Elbe River bottom sediments to determine the correlation between the element composition and the grain size in the $ \\\\le $4, 4--8, 8--16, 16--32, 32--63 7m and bulk samples $ \\\\le $63 7m fractions. The purpose of this

Zden?k Borovec

2000-01-01

222

Photometric determination of rare-earth elements with arsenazo III in glasses with titanium  

SciTech Connect

This paper develops a method of determining rare-earth elements in the presence of large quantities of titanium in glasses designed for work under conditions of intensive luminous fluxes. The authors improve the procedure by selecting a masking reagent to eliminate the interfering influence of titanium. The method was tested on artificial mixtures prepared from quartz glasses, alloyed with titanium and rare-earth oxides. The proposed method is distinguished by simplicity, speed (without considering decomposition of the sample, the time of analysis is 25 min), and gives readily reproducible results.

Nesterova, M.D.

1986-08-01

223

Element for separating gaseous isotopes into at least two fractions and with a separating basket consisting of several separating elements  

SciTech Connect

A separating element for gaseous isotopes into two fractions, and consisting of several elongated separating chips with a row of entry openings for the process gas at one side of the chips and a row of exit openings for the heavy fraction at the other side of the chips, with exit openings for the light fraction at the edges of the chips, and of two tubes holding the chips and having at least one chamber, with said tubes being connected by means of connecting elements, and equipped with entry and exit openings on their contact surfaces, with said entry and exit openings arranged in rows in a longitudinal direction of the chips, and for simplifying of installation and construction, this invention provides that the chips are arranged in a longitudinal direction to the tubes, with their sides abutting directly against the smooth contact surfaces of the tubes, and whereby the connecting elements are positioned in one row in the center of the two tubes.

Grossstuck, W.; Schafer, R.

1985-07-09

224

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

NASA Astrophysics Data System (ADS)

Major and trace element zonation patterns were determined in ultrahigh-pressure eclogite garnets from the Western Gneiss Region (Norway). All investigated garnets show multiple growth zones and preserve complex growth zonation patterns with respect to both major and rare earth elements (REE). Due to chemical differences of the host rocks two types of major element compositional zonation patterns occur: (1) abrupt, step-like compositional changes corresponding with the growth zones and (2) compositionally homogeneous interiors, independent of growth zones, followed by abrupt chemical changes towards the rims. Despite differences in major element zonation, the REE patterns are almost identical in all garnets and can be divided into four distinct zones with characteristic patterns. In order to interpret the major and trace element distribution and zoning patterns in terms of the subduction history of the rocks, we combined thermodynamic forward models for appropriate bulk rock compositions to yield molar proportions and major element compositions of stable phases along the inferred pressure-temperature path with a mass balance distribution of REEs among the calculated stable phases during high pressure metamorphism. Our thermodynamic forward models reproduce the complex major element zonation patterns and growth zones in the natural garnets, with garnet growth predicted during four different reaction stages: (1) chlorite breakdown, (2) epidote breakdown, (3) amphibole breakdown and (4) reduction in molar clinopyroxene at ultrahigh-pressure conditions. Mass-balance of the rare earth element distribution among the modelled stable phases yielded characteristic zonation patterns in garnet that closely resemble those in the natural samples. Garnet growth and trace element incorporation occurred in near thermodynamic equilibrium with matrix phases during subduction. The rare earth element patterns in garnet exhibit distinct enrichment zones that fingerprint the minerals involved in the garnet-forming reactions as well as local peaks that can be explained by fractionation effects and changes in the mineral assemblage.

Konrad-Schmolke, Matthias; Zack, Thomas; O'Brien, Patrick J.; Jacob, Dorrit E.

2008-07-01

225

Element fractionation by sequential extraction in a soil with high carbonate content  

Microsoft Academic Search

The influence of carbonate and other buffering substances in soils on the results of a 3-step sequential extraction procedure (BCR) used for metal fractionation was investigated. Deviating from the original extraction scheme, where the extracts are analysed only for a limited number of metals, almost all elements in the soils were quantified by X-ray fluorescence spectroscopy, in the initial samples

Margareta Sulkowski; Alfred V. Hirner

2006-01-01

226

Rare earth element patterns in a Chinese stalagmite controlled by sources and scavenging from karst groundwater  

NASA Astrophysics Data System (ADS)

The rare earth elements and yttrium (REY) in a Chinese stalagmite (SJ3) have been studied to delineate their possible sources and controlling mechanisms. The following results are obtained: (1) The REY in karst groundwater at the study site have very low concentrations, e.g. ranging from 59 × 10-6 to 614 × 10-6 ?mol/L for La, and are transported predominantly in particle/colloidal phases.These elements show a high linear positive correlation with Fe, Mn and Al (r2 = 0.98, 0.95 and 0.91, respectively), which are also transported largely in particle/colloidal phases, suggesting a close association of REY with Fe, Mn and Al in colloidal/particle phases; (2) REY mobilization from the sources, i.e. the limestone host rock and the overlying soil layer, may not have exerted a significant influence on the REY patterns for SJ3 including anomalies of La, Ce and Y and fractionation between light and heavy REY; (3) The REY patterns of SJ3 display significant variations which are controlled in part by change in contributions from the limestone host rock and the overlying soil layer and can be associated with stadial-interstadial changes in past climate and environment. The REY contribution from the overlying soil layer is higher under a warm-humid climate phase than a cold-dry one and the REY contribution from the limestone host rock is reversed; (4) Some of the variations of the SJ3 REY patterns could not be explained with a simple mixing of different REY sources. Removal of REY from the groundwater in association with precipitation of colloidal and particle materials, an analogue to REY scavenging from seawater, is the most important mechanism influencing the SJ3 REY patterns. Strong REY "scavenging", which may be caused by both less dynamic hydrology, longer travel-time and increased ionic strength of karst groundwater, is suggested to be responsible for the large positive Y anomalies and negative Ce anomalies and depletion of light REE relative to heavy REE during the cold-dry climate phases (e.g. the periods corresponding to the last glacial maximum and Heinrich event 1).

Zhou, Houyun; Greig, Alan; Tang, Jing; You, Chen-Feng; Yuan, Daoxian; Tong, Xiaoning; Huang, Ying

2012-04-01

227

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

228

The effect of rare earth elements on the texture and formability of asymmetrically rolled magnesium sheet  

SciTech Connect

The lack of formability is a serious issue when considering magnesium alloys for various applications. Standard symmetric rolling introduces a strong basal texture that decreases the formability; however, asymmetric rolling has been put forward as a possible route to produce sheet with weaker texture and greater ductility. It has also been shown in recent work that weaker textures can be produced through the addition of rare earth elements to magnesium alloys. Therefore, this study has been carried out to investigate the effect of rare earth additions on the texture changes during asymmetric rolling. Two alloys have been used, AZ31B and ZEK100. The effect that the rare earth additions have on the texture of asymmetrically rolled sheet and the subsequent changes in formability will be discussed.

Alderman, Dr. Martyn [Magnesium Elektron North America; Cavin, Odis Burl [ORNL; Davis, Dr. Bruce [Magnesium Elektron North America; Muralidharan, Govindarajan [ORNL; Muth, Thomas R [ORNL; Peter, William H [ORNL; Randman, David [Magnesium Elektron North America; Watkins, Thomas R [ORNL

2011-01-01

229

Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China  

Microsoft Academic Search

The Lesser Qinling carbonatite dykes are mainly composed of calcites. They are characterized by unusually high heavy rare earth element concentrations (HREE; e.g. Yb>30 ppm) and flat to weakly light rare earth element (LREE) enriched chondrite-normalized patterns (La\\/Ybn=1.0–5.5), which is in marked contrast with all other published carbonatite data. The trace element contents of calcite crystals were measured in situ by

Cheng Xu; Ian H. Campbell; Charlotte M. Allen; Zhilong Huang; Liang Qi; Huan Zhang; Guishan Zhang

2007-01-01

230

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

NASA Astrophysics Data System (ADS)

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

Collerson, K.; Kamber, B.

2001-12-01

231

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

National Technical Information Service (NTIS)

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, fat...

2004-01-01

232

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

233

Heterogeneous Accretion of the Earth and the Timing of Volatile Element Depletion  

NASA Astrophysics Data System (ADS)

The Earth is depleted in moderately volatile elements relative to CI chondrites and thus average solar system material. The timing of this depletion has been a matter of debate. Isotopic constraints from the short-lived Pd-Ag, Mn-Cr and Hf-W decay systems can be used to model the accretion history of the Earth and the timing of moderately volatile element depletion [1]. While the Pd-Ag decay system provides evidence for the accretion of volatile-rich material, other systems like Mn-Cr and Rb-Sr require that the Earth accreted volatile-depleted material [2, 3]. As recently shown [1], the contrasting evidence from these decay systems can be reconciled by heterogeneous accretion, which implies that the composition of the material from which the Earth accreted changed over time. A continuous core formation model was used and the best match was obtained for the Earth mainly accreting volatile-depleted material in the beginning and more volatile-rich material towards the end, while core formation was still ongoing [1]. However, a different study proposed that the bulk of the moderately volatile elements was delivered in a volatile-rich late veneer after core formation ceased [4]. This is not supported by the Pd-Ag data (Ag is a moderately volatile element, while Pd is more refractory). A late veneer of volatile-rich CI material (Pd = 556 ppb and Ag = 197 ppb) after core formation is limited to a maximum of ~0.4 % of the Earth's mass by the Pd concentration of the Earth's mantle today (~3.3 ppb). This amount of CI material does not supply enough Ag to substantially modify the Ag isotope composition of the Earth's mantle. In a scenario where the Earth accretes exceedingly volatile depleted material, its high Pd/Ag ratio would lead to an extreme radiogenic Ag isotope composition of the bulk silicate Earth (BSE), which cannot be counterbalanced by the late veneer to match the observed BSE composition. We also tested the heterogeneous accretion scenario using N-body accretion simulations [5] for the Pd-Ag decay system. Again the best results were obtained when materials with different degrees of volatile depletion (= different Pd/Ag ratios) were accreted. The simulations include early accretion of close-in material and later accretion of material from greater heliocentric distances, which is consistent with a transition from volatile-depleted to volatile-enriched material. Therefore, N-body accretion simulations and the continuous core formation model yield similar results, which demonstrates the robustness of the heterogeneous accretion scenario. [1] Schönbächler et al. (2010), Science 328, 884. [2] Carlson & Lugmair (1988), Earth Planet Sci. Lett. 90, 119. [3] Qin et al. (2009), Geochim. Cosmochim. Acta 74, 1122. [4] Albarède (2009), Nature, 461, 1227.[5] O'Brien et al. (2006), Icarus 184, 36.

Schönbächler, M.; Nimmo, F.

2011-12-01

234

Low-Molecular-Weight-Organic-Acids as Extractant to Predict Plant Bioavailability of Rare Earth Elements  

Microsoft Academic Search

A mixture of malic acid and citric acid as extractant for the evaluation of plant bioavailability of rare earth elements (REEs) in soils is presented. Extractable REEs by malic-citric acid, acetic acid (CH3COOH), DTPA, EDTA, Mehlich 3 and total REEs in soils were compared with the REEs in winter wheat (Triticum aestivum L.) grown in the soils in greenhouse. Malic-citric

Shuzhen Zhang; Xiao-Quan Shan; Fuliang Li

2000-01-01

235

Isolation and characterization of rare earth element-binding protein in roots of maize  

Microsoft Academic Search

Rare earth element-binding protein was isolated from maize, which was grown under greenhouse conditions and characterized\\u000a in terms of molecular weight, amino acid composition, and ultraviolet absorption. The molecular weight of the maize protein\\u000a was determined to be 183,000, with two distinct subunits of approximately molecular weights of 22,000 and 69,000, respectively.\\u000a The protein is particularly rich in asparagine\\/aspartic acid,

Dong-an Yuan; Xiao-quan Shan; Bei Wen; Qing Huai

2001-01-01

236

Determination of rare-earth elements in coal using microwave digestion and gradient ion chromatography  

Microsoft Academic Search

The combined application of microwave digestion, high-performance ion chromatography (HPIC) and on-line sample solution concentration provides a technique for the routine determination of rare-earth elements (REE) in coals. Acid dissolution of whole powdered coal samples using microwave pressure digestion removes the necessity of dry ashing to eliminate organic carbon, providing considerable time savings and significantly reducing the risk of sample

Ronald T. Watkins; Moira K. Ridley; M. A. Bruno Pougnet; James P. Willis

1995-01-01

237

High-resolution spectrometric analysis of rare earth elements-activated cathodoluminescence in feldspar minerals  

Microsoft Academic Search

Cathodoluminescence (CL) investigations of igneous, metamorphic and sedimentary feldspars indicate that rare earth elements (REE)-activated CL in feldspars is more common than previously assumed. Hot-cathode CL microscopy combined with high-resolution spectrometric analysis of CL emission allow to detect some REE below the detection limits of electron microprobe and proton-induced X-ray emission analysis (PIXE) and reveal variations in the REE distribution

Jens Götze; Dirk Habermann; Rolf D Neuser; Detlev K Richter

1999-01-01

238

Behaviour of rare earth elements during seawater\\/basalt interactions in the Mururoa Massif  

Microsoft Academic Search

The rare earth elements (REE) were analysed in the interstitial fluids, in the basalts and in the alteration products (clays and zeolites) of Mururoa atoll volcanic rocks (French Polynesia) in order to investigate REE behaviour during seawater\\/basalt interactions at low temperature. The REE distribution coefficients between fluids and secondary products were calculated using the EQ3\\/6 geochemical code. The reversible\\/irreversible character

C Guy; V Daux; J Schott

1999-01-01

239

Comparative study of yttrium and rare-earth element behaviours in fluorine-rich hydrothermal fluids  

Microsoft Academic Search

The mineral ‘fluorite’ is utilized as a probe to investigate the behaviour of the pseudolanthanide yttrium with respect to the lanthanides (rare-earth elements, REE) in fluorine-rich hydrothermal solutions. Hydrothermal vein fluorites are characterized by the close association of Y and REE, but in contrast to igneous and clastic rocks they show variable and nonchondritic Y\\/Ho ratios of up to 200.

Michael Bau; Peter Dulski

1995-01-01

240

Depletion of heavy rare-earth elements in metamorphic minerals from Adirondack anorthosites  

Microsoft Academic Search

Repartitioning of rare-earth elements (REE) during the Grenville granulite facies metamorphism of Adirondack anorthosite has produced metamorphic minerals depleted in the heavy REE relative to concentrations predicted by igneous partition coefficients. The heavy- REE depletion is observed in garnet-bearing metamorphosed anorthosites and results from closed-system repartitioning of REE among heavy-REE-rich garnet and other recrystallizing minerals. The resulting heavy-REE-depleted patterns contrast

Karl E. Seifert; Sarah A. Chadima

1989-01-01

241

INSIGHTS FROM RARE EARTH ELEMENTS INTO THE GENESIS OF THE BUCK CREEK COMPLEX, CLAY COUNTY, NC  

Microsoft Academic Search

The Buck Creek complex is among the largest and most lithologically diverse of the mafic\\/ultramafic bodies found in the eastern Blue Ridge province of the southern Appala- chians. Rare-earth element (REE) analyses on a representative suite of Buck Creek am- phibolites and meta-troctolites supplements an ongoing undergraduate research pro- gram examining the origins and history of mafic\\/ultramafic units in southwestern

SUZETTE BERGER; DEBORAH COCHRANE; KYLA SIMONS; IVAN SAVOV; J. G. RYAN; V. L. P ETERSON

242

Light Rare Earth Elements enrichment in an acidic mine lake (Lusatia, Germany)  

Microsoft Academic Search

The distribution of Rare Earth Elements (REE) was investigated in the acidic waters (lake and groundwater) of a lignite mining district (Germany). The Fe- and SO4-rich lake water (pH 2.7) displays high REE contents (e.g. La?70 ?g\\/l, Ce?160 ?g\\/l) and an enrichment of light REE (LREE) in the NASC normalised pattern. Considering the hydrodynamic model and geochemical data, the lake

Elke Bozau; Marc Leblanc; Jean Luc Seidel; Hans-Joachim Stärk

2004-01-01

243

Rare-earth elements and genesis of lamprophyres in the Laowangzhai gold orefield, Yunnan Province  

Microsoft Academic Search

The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailao tectonic zone, Yunnan Province, is a typical\\u000a gold orefield where lamprophyres are temporally and spatially related to gold mineralization. Major element data show that\\u000a lamprophyres in the orefield are of alkalic series and can be divided into potassic and K-rich calc-alkaline lamprophyres.\\u000a The rocks are enriched in rare-earth

Huang Zhilong; Zhu Chengming; Wang Liankui

1996-01-01

244

Population growth responses of Tetrahymena shanghaiensis in exposure to rare earth elements  

Microsoft Academic Search

This article presents the population growth responses of Tetrahymena shanghaiensis s1 in exposure to rare earth elements (REEs). Both the light REEs (La, Sm) and the heavy REEs (Y, Gd) were investigated with\\u000a 24- and 96-hr population growth assays to evaluate their aquatic toxicity. Four end points, cell count, frequency of neutral\\u000a red (NR) uptake, total protein, and nucleic acid

Yongxing Wang; Min Zhang; Xiaorong Wang

2000-01-01

245

Complexation of trivalent rare earth elements (Ce, Eu, Gd, Tb, Yb) by carbonate ions  

Microsoft Academic Search

Carbonate stability constants for five rare earth elements (Ce[sup 3+], Eu[sup 3+], Gd[sup 3+], Tb[sup 3+], and Yb[sup 3+]) have been determined at t = 25[degrees]C and 0.70 [plus minus] 0.02 M ionic strength through solvent exchange techniques. Estimated stability constants for Ce, Eu, and Yb are in close agreement with previous work. Analyses using Gd and Tb provide the

Jong Hyeon Lee; R. H. Byrne

1993-01-01

246

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

Microsoft Academic Search

The concentration of rare earth elements and yttrium (REE + Y) was determined in Holocene Mg-calcite microbialites from shallow reef framework cavities at Heron Reef, Great Barrier Reef. Shale-normalized REE + Y patterns of 52 microbialite samples show: (1) uniform heavy REE enrichment (NdSN\\/YbSN = 0.236, SD = 0.026); (2) consistent negative Ce and positive La anomalies; (3) marine Y\\/Ho

Gregory E. Webb; Balz S. Kamber

2000-01-01

247

Behaviour of rare earth elements during submarine weathering of tholeiitic basalt  

Microsoft Academic Search

DREDGED oceanic basalts and those sampled by deep-ocean drilling have commonly undergone some weathering with subsequent changes in their chemical composition1-7. The rare-earth elements (REE) La-Lu are generally considered to be unaffected by weathering and are thus often used to characterise variations in basalt and magma composition. When considered relative to chondritic abundances8, the overall REE distribution is a critical

John N. Ludden; Geoffrey Thompson

1978-01-01

248

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

Microsoft Academic Search

Rare earth element (REE) and yttrium (Y) concentrations were measured in fluids collected from deep-sea hydrothermal systems including the Mid-Atlantic Ridge (MAR), i.e., Menez Gwen, Lucky Strike, TAG, and Snakepit; the East Pacific Rise (EPR), i.e., 13°N and 17–19°S; and the Lau (Vai Lili) and Manus (Vienna Woods, PacManus, Desmos) Back-Arc Basins (BAB) in the South-West Pacific. In most fluids,

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

1999-01-01

249

Rare earth elements in chloride-rich groundwater, Palo Duro Basin, Texas, USA  

Microsoft Academic Search

Rare earth element (REE) data for groundwater samples from the Deep-Basin Brine aquifer of the Palo Duro Basin, Texas, USA, illustrates the potential use of REE for inferring groundwater flow paths through different geologic materials. The REE content of the groundwaters range over 2.5 orders of magnitude and are depleted by 10² to 10⁵ relative to aquifer materials. The shale-normalized

D. C. Gosselin; M. R. Smith; E. A. Lepel; J. C. Laul

1992-01-01

250

Oceanic crustal thickness from seismic measurements and rare earth element inversions  

Microsoft Academic Search

Seismic refraction results show that the igneous section of oceanic crust averages 7.1 [plus minus] 0.8 km thick away from anomalous regions such as fracture zones and hot-spots, with extremal bounds of 5.0-8.5 km. Rare earth element inversions of the melt distribution in the mantle source region suggest that sufficient melt is generated under normal oceanic spreading centers to produce

Robert S. White; Dan McKenzie; R. K. ONions

1992-01-01

251

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

Microsoft Academic Search

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

Hiroshi Maeda; Yoshiaki Tanaka; Masao Fukutomi; Toshihisa Asano

1988-01-01

252

Removal of Rare Earth Elements and Precious Metal Species by Biosorption  

Microsoft Academic Search

\\u000a In Rare Earth Elements (REE) or Precious Metal Species (PMS) removal many types of biological phenomena can take place, such\\u000a as biosorption, bioaccumulation, resistance\\/detoxification mechanisms, and direct or indirect utilization in the microbial\\u000a metabolism. The high demand for the REE or PMS implies demand on increased production of ores containing REE or PMS (i.e.\\u000a mining) and recycling of solutions to

Yves Andrès; Claire Gérente

253

Determination of rare earth elements in rocks and meteorites by the radioactivation method  

Microsoft Academic Search

Methods of digestion of samples by acidic dissolution and in fused sodium peroxide were modified in conformity with the chemical\\u000a composition of basalts, periotites and stone meteorites as well as the method of REE pre-concentration by the lanthanum fluoride\\u000a cycle. The enriching methods were used for the neutron-activation determination of the individual rare-earth elements in rocks\\u000a and meteorites with a

G. M. Kolesov; V. I. Fernadsky

1976-01-01

254

Colloidal Control on the Distribution of Rare Earth Elements in Shallow Groundwaters  

Microsoft Academic Search

A 7-year monitoring period of rare earth element (REE) concentrations and REE pattern shapes was carried out in well water\\u000a samples from a 450 m long transect setup in the Kervidy\\/Coët-Dan experimental catchment, France. The new dataset confirms\\u000a systematic, topography-related REE signatures and REE concentrations variability but challenges the validity of a groundwater\\u000a mixing hypothesis. Most likely, this is due to

Olivier Pourret; Gérard Gruau; Aline Dia; Mélanie Davranche; Jérôme Molénat

2010-01-01

255

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

256

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

Microsoft Academic Search

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

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

1997-01-01

257

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

Microsoft Academic Search

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

P. H. OlinJ; J. A. Wolff

2010-01-01

258

Effect of rare earth elements on the thermal cracking resistance of high speed steel rolls  

Microsoft Academic Search

The effect of rare earth elements on the thermal cracking resistance of high speed steel (HSS) rolls was investigated. Laser rapid heating was used for thermal fatigue experiments. Thermal cracks and microstructure were observed using metalloscopy and scanning electron microscopy. The results showed that thermal cracks initiated from the interface between the matrix and eutectic carbides (including M6C and M7C3

Mingjia WANG; Yanmei LI; Zixi WANG; Er BAO

2011-01-01

259

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

PubMed Central

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

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

2008-01-01

260

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

2012-02-29

261

Stability Constants for Sulfate Complexation of Yttrium and the Rare Earth Elements  

NASA Astrophysics Data System (ADS)

In natural waters, yttrium and the rare earth elements (YREE) are mostly complexed with inorganic anions such as carbonate and chloride. YREE complexation with sulfate is minor (<5%) in seawater and generally negligible in fresh waters, yet it can be quite important in situations where oxidation of pyrite leads to high dissolved sulfate concentrations. The development of a consensus pattern of stability constants for YREE monosulfato-complexes has a quite convoluted history. It is based on a 1974 'compilation' that was derived from a much older, somewhat questionable, dataset, by adding interpolations and omitting a few elements. During subsequent transcriptions, some errors were introduced and the omitted data were interpolated rather than replaced with the original values. All this has resulted in a consensus pattern that is essentially flat, without any structure or fractionation between light and heavy REE. It is widely quoted and has been used to argue that sulfate complexation does not cause YREE fractionation. Conversely, flat YREE patterns in natural waters have been taken as evidence for substantial complexation of the YREE with sulfate. We have taken a new approach to measuring the stability constants of all YREE monosulfato-complexes with the greatest possible precision. Stability constants were determined by comparing the solubility of barium sulfate in YREE chloride solutions and in an ammonium chloride reference solution, all at the ionic strength of seawater. The reference solution and solutions of individual YREE chlorides were equilibrated with a small amount of high purity barium sulfate at t = 25°C for at least one week. The equilibrated solutions were then filtered and analyzed for concentrations of YREE and Ba (ICP-MS), chloride and sulfate (ion chromatography), and pH (glass electrode). A simple model was used to determine the stability constants from these measurements. Averaged results from four experiments, two with and two without added sulfate, have standard deviations of 0.03 log units or less. Within this precision, the pattern of stability constants is not flat, as has been assumed, but has a very distinct shape. The pattern is nearly flat from La to Gd, possibly with a slight maximum at Eu. From Gd to Lu it shows a gradual and almost linear decrease, with the stability constant of Lu being more than 0.2 log units below that of La. The stability constant of Y is close to that of Er. Our pattern is in broad agreement with several careful earlier studies that have been largely ignored in the recent literature. Comparison with the substantial body of existing work also indicates that our stability constants are well within the published range for individual YREE. This revised pattern may have significant consequences for the interpretation of YREE patterns in high-sulfate environments such as runoff from mine tailings and certain groundwaters.

Schijf, J.; Byrne, R. H.

2002-12-01

262

Effects of rare earth elements on the growth of Cistanche deserticola cells and the production of phenylethanoid glycosides.  

PubMed

The rare earth elements Nd, La, Ce at proper concentrations had positive effects on the cell growth of Cistanche deserticola and production of phenylethanoid glycosides (PeG). A mixture of rare earth elements (MRE, La(2)O(3):CeO(2):Pr(6)O(11):Sm(2)O(3)=255:175:3:1, mol/mol) showed the most remarkable effects. After 30 day's culture, 0.02 mmoll(-1) MRE gave the highest content (20.8%) and production (1.6 gl(-1)) of PeG, which were 104 and 167% higher than those obtained in control (without rare earth elements). PMID:12697390

Ouyang, Jie; Wang, Xiaodong; Zhao, Bing; Yuan, Xiaofan; Wang, Yuchun

2003-04-24

263

Determination of picogram quantities of rare-earth elements in meteoritic materials by direct-loading thermal ionization mass spectrometry  

SciTech Connect

A procedure for direct-loading isotope dilution mass spectrometry (DL-IDMS) of rare-earth elements (REE), alkaline-earth metals, (Mg, Ca, Sr, and Ba), alkali metals (K and Rb), and iron in microcomponents of meteorites is described. Without chemical separation the acid-decomposed sample was directly loaded onto a mass spectrometer filament and subjected to thermal ionization mass spectrometry with careful control of the filament current and the oxygen partial pressure. This technique permits, on a routine basis, precise concentration determinations of individual REE at the levels of > 10/sup /minus/13/ g (or > 10/sup /minus/15/ mol) in meteroritic and terrestrial materials such as chondrules, mineral fragments, and basaltic samples. The results demonstrate the presence of highly fractionated REE in microcomponents of meteorites, which indicates a new chemical aspect of REE in the early planetary materials. The DL-IDMS technique can thus be used as the only means of high-precision analyses of small planetary materials with low REE contents.

Nakamura, N.; Yamamoto, K.; Noda, S.; Nishikawa, Y.; Komi, H.; Nagamoto, H.; Nakayama, T.; Misawa, K.

1989-04-01

264

Fractionation, sources and budgets of potential harmful elements in surface sediments of the East China Sea.  

PubMed

Total concentrations, chemical fractions by BCR procedure and enrichment factors of nine potential harmful elements (V, Cr, Co, Ni, Cu, Zn, Mo, Cd and Pb) in surface sediments of the East China Sea (ECS) were investigated. Spatial distributions illustrated that PHEs (potential harmful elements) were mainly from the Changjiang River and the Jiangsu coastal current, except Pb which was influenced by atmospheric input. Sediments in the ECS were moderately polluted with Cd, Pb, Zn and Cu according to their enrichment factors (EFs). Distributions of EFs and labile fractions revealed that anthropogenic Cd and Cu were mainly input though the Changjiang, Pb pollutant was delivered from the Changjiang and atmosphere, while Zn was impacted by terrestrial pollution from the Changjiang and the Hangzhou Bay. Budget calculation showed that the Changjiang contributed 82-90% of PHE influxes. Thirty-eight to 77% of PHEs were buried in sediment, mainly along the inner shelf. PMID:23265773

Yu, Yu; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning

2012-12-22

265

Monopole Elements with Disk Ground Planes on Flat Earth: Atlas of Directivity, Radiation Efficiency, Radiation Resistance, and Input Impedance.  

National Technical Information Service (NTIS)

Richmond's moment-method programs RICHMOND3 and RICHMOND4 for monopole elements with disk ground planes above flat Earth are used to obtain computer plots of directivity, radiation efficiency, radiation resistance, and input impedance at 15 MHz. Results, ...

M. M. Weiner

1992-01-01

266

Monopole elements with disk ground planes on flat earth: Atlas of directivity, radiation efficiency, radiation resistance, and input impedance  

Microsoft Academic Search

Richmond's moment-method programs RICHMOND3 and RICHMOND4 for monopole elements with disk ground planes above flat Earth are used to obtain computer plots of directivity, radiation efficiency, radiation resistance, and input impedance at 15 MHz. Results, in the form of an atlas, are presented as a function of Earth classification for thin, quarter-wave monopole elements whose ground planes or radii 0

M. M. Weiner

1992-01-01

267

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

Microsoft Academic Search

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

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

1996-01-01

268

Photosystem 2 activities of hyper-accumulator Dicranopteris dichotoma Bernh from a light rare earth elements mine  

Microsoft Academic Search

The distribution of rare earth elements (REEs) in the fern Dicranopteris dichotoma Bernh plants from a light rare earth elements mine (LRM) and a non-mining (NM) area in Longnan county of Jiangxi province,\\u000a China were investigated by means of inductively coupled plasma-mass spectrometry, transmission electron microscopy, and energy-dispersive\\u000a X-ray microanalysis. The photosynthetic characteristics of D. dichotoma were studied by chlorophyll

L. F. Wang; H. B. Ji; K. Z. Bai; L. B. Li; T. Y. Kuang

2006-01-01

269

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

270

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

2011-08-16

271

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

2007-01-08

272

TES microcalorimeter SEM-EDS system for rare-earth elements analyses  

NASA Astrophysics Data System (ADS)

A field-emission scanning electron microscope (FE-SEM) with energy-dispersive X-ray spectrometer (EDS) detector of a superconducting transition-edge sensor (TES) microcalorimeter is a new system for electron-microprobe chemical analyses. FE-SEM with TES was used for qualitative and semi-quantitative analyses of rare-earth elements (REE) at a low accelerating voltage of 5 kV. Four characteristic M-lines were detected in the LaB6 spectrum: LaM? at 640, LaM?? at 841, LaM? at 1021, and a weak line (M2N4 transition) at 1100 eV. The spectra of other rare-earth borides, rare-earth phosphates, and monazite were assigned in the same way as the La M-lines were. For quantitative analyses, we used a calibration curve method, using standard specimens of known chemical compositions. Linear calibration curves for plots of P, Ca, La, Ce, Pr, and Nd intensities versus each weight percentage were obtained. Semi-quantitative analyses of rare-earth minerals should be carried out at low accelerating voltages using a calibration curve method. In a TES-EDS system, a low accelerating voltage can be used to improve the spatial resolution, without the sensitivity disadvantages of low-energy X-ray emissions. Moreover, a strong increase in the M?? intensity with increasing atomic number Z was seen, so the detection limits of heavy REE was much lower than those of light REEs. These results suggest that the TES-EDS system could be a useful analytical tool in rare-earth mineralogy.

Uehara, Seiichiro; Takai, Yasuhiro; Shirose, Yohei; Fujii, Yuki

273

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

PubMed

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

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

2013-07-12

274

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

275

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

Microsoft Academic Search

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

Xiong Yongliang; Zhai Yusheng

1991-01-01

276

Studies of rare earth element distribution and action in human erythrocyte and animal hepatocyte by PIXE  

NASA Astrophysics Data System (ADS)

PIXE analysis is applied to investigate a long-term disputed issue whether the rare earth element (REE) can enter the cell across the cell membrane or not. It has been illustrated that REE could travel across the biomembrane into the cells by cell studies in vitro as well as in studies of animals fed with REEs diet. The binding of REE by membrane changes its permeability and makes intracellular ion transportable. Entrance of REEs may influence the cellular function. In addition, the REE distribution and behavior in cell are discussed.

Wu, Y. P.; Mi, Y.; Shen, H.; Yao, H. Y.; Cheng, Y.; Wang, X.; Zhang, J. X.

2002-04-01

277

Effect of rare-earth elements on luminescence properties of ZnSe-based Chalcogenide scintillators  

NASA Astrophysics Data System (ADS)

Afterglow in two types of semiconductor scintillators, ZnSe(Te) and ZnSe(O,Al), after pulsed X-ray excitation is studied. It is demonstrated that the afterglow can be significantly reduced by annealing in a zinc-rich atmosphere and co-doping by rare-earth elements. The co-doping also decreases the light yield of the ZnSe(Te) crystal, but has a minor influence on the light yield of annealed ZnSe(O,Al). The influence of the co-doping on carrier trapping is discussed.

Katrunov, K. A.; Starzhinskiy, N. G.; Malyukin, Yu. V.; Silin, V. I.; Zenya, I. M.; Tamulaitis, G.

2010-10-01

278

Rare earth elements in the peats of Moscow and Tver oblasts  

NASA Astrophysics Data System (ADS)

Noticeable amounts of rare-earth elements were first detected in the peats of the earlier drained bogs of Moscow and Tver oblasts. The analysis was carried out by inductively coupled plasma mass spectrometry on an ELAN DRC II instrument (PerkinElmer, United States). The contents of REEs in peat ash of certain deposits are higher than their average contents in the basic rocks and vary in the range of 0.5-60 and 0.1-41.3 mg/kg for the cerium and yttrium groups, respectively.

Savvin, S. B.; Akhmet'eva, N. P.; Mikhailova, A. V.; Ermolaeva, V. N.; Podkolzin, I. V.

2013-01-01

279

Plant consisting of modular elements for degrading organic wastes by means of earth worms  

US Patent & Trademark Office Database

A plant consisting of modular elements for reducing organic wastes by degrading them by means of earth worms, comprising a tank for organic wastes, arranged outside the plant assembly, an inclined main screw feeder for lifting the materials onto work stations and discharging them onto horizontal screw-feeders arranged at any work station, the horizontal feeders conveying the materials to horizontal conveyers which discharge them into modular containers arranged on the work stations, whereby, at the end of the transformation, the material is discharged through hoppers onto conveyors arranged at the plant base and conveyed to storage containers.

Grappelli; Adriana (Rome, IT); Tomati; Umberto (Rome, IT); Palma; Grazio (Mentana, IT)

1985-11-12

280

The behavior of volatile elements during the formation and evolution of the Earth and planetary cores  

NASA Astrophysics Data System (ADS)

Core formation is one of the major events in early planetary differentiation. For terrestrial planets, an efficient way to form the core is through gravitational segregation in a magma ocean. The hypothesis of core formation in a deep magma ocean has been tested by experimental results on the partitioning of siderophile/chalcophile elements under high pressures and high temperatures. While abundant data have been reported for refractory elements, those on volatile elements are relatively sparse. Here, we review the existing data on the partitioning of volatile elements between core-forming alloys and mantle silicates under the pressure and temperature conditions that are pertinent to the formation and evolution of the Earth and planetary cores. We will also report new experimental data on the partitioning of a number of volatile elements (including Cu, Zn, Ga, Ge, Ag, and Pb) between liquid Fe-Ni-S alloy and liquid silicate, up to 20 GPa and 2273 K. The implications for the origin and evolution of terrestrial cores will be discussed.

Li, J.; Horn, I.; McDonough, W. F.; Rudnick, R.; Agee, C. B.

2003-04-01

281

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

282

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

283

Biosorption of Uranium and Rare Earth Elements Using Biomass of Algae  

PubMed Central

In order to investigate the behavior of rare earth elements (REEs) and uranium (U) in marine organism, the concentrations of REEs and U in some brown algae samples taken on the coast of Niigata Prefecture were determined. In addition, laboratory model experiment to uptake these elements using living and dried algae (Undaria pinnatifida and Sargassum hemiphyllum) was also carried out to survey the uptake and bioaccumulation mechanism of REEs and U in algae. Consequently, the following matters have been mainly clarified. (1) The order of the concentration of REEs for each organ in Sargassum hemiphyllum is “main branch” > “leaf” > “vesicle,” however for U, the order is “leaf” > “vesicle” > “main branch.” (2) The concentration of REEs in Sargassum hemiphyllum may be strongly affected by suspended solid in seawater. (3) The uptake and/or accumulate mechanism of REEs in brown algae may be different from that of U.

Sakamoto, Nobuo; Kano, Naoki; Imaizumi, Hiroshi

2008-01-01

284

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

285

Trace rare earth element analysis of IAEA hair (HH-1), animal bone (H-5) and other biological standards by radiochemical neutron activation  

SciTech Connect

A radiochemical neutron activation analysis using a rare earth group separation scheme has been used to measure ultratrace levels of rare earth elements (REE) in IAEA Human Hair (HH-1), IAEA Animal Bone (H-5), NBS Bovine Liver (SRM 1577), and NBS Orchard Leaf (SRM 1571) standards. The REE concentrations in Human Hair and Animal Bone range from 10/sup -8/g/g to 10/sup -11/g/g and their chondritic normalized REE patterns show a negative Eu anomaly and follow as a smooth function of the REE ionic radii. The REE patterns for NBS Bovine Liver and Orchard Leaf are identical except that their concentrations are higher. The similarity among the REE patterns suggest that the REE do not appear to be fractionated during the intake of biological materials by animals or humans. 14 refs., 3 figs., 2 tabs.

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

1986-03-01

286

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

Microsoft Academic Search

As one fundamental part of the global recycling process between the Earth's mantle and lithosphere, sinking slabs in the deep mantle play a crucial role on mantle geochemical evolution. Many previous studies in the mantle dynamics subject area focused on understanding how stirring and mixing acts in the convective mantle, and thus how slab heterogeneities are spread out through the

S. Ferrachat; L. H. Kellogg

2001-01-01

287

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

NASA Astrophysics Data System (ADS)

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.

Zheng, Liugen; Liu, Guijian; Chou, Chen-Lin; Qi, Cuicui; Zhang, Ying

2007-10-01

288

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

SciTech Connect

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

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

1997-04-09

289

Experimental partitioning of high field strength and rare earth elements between clinopyroxene and garnet in andesitic to tonalitic systems  

Microsoft Academic Search

Partition coefficients of the rare earth elements (REE) and the high field strength elements (HFSE: Ti, Zr, Hf, Nb, Ta) among clinopyroxenes, garnets, and andesitic to granodioritic melts were experimentally determined at pressures ranging from 1 to 3 GPa and temperatures between 900 and 1150°C. Natural rocks of quartz–dioritic and basaltic composition were used as starting materials. Melt compositions covered

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

2000-01-01

290

Origin of anomalous rare-earth element and yttrium enrichments in subaerially exposed basalts: Evidence from French Polynesia  

Microsoft Academic Search

Basalts from French Polynesian islands occasionally display extremely high abundances and anomalous distributions of rare-earth elements (REE) and yttrium, whereas other incompatible element concentrations and O, Sr, Nd and Pb isotopic ratios do not differ from those of “normal” basalts from the same area. The REE- and Y-enriched basalts contribute up to 15% of the sample set, suggesting that this

J. Cotten; A. Le Dez; M. Bau; M. Caroff; R. C. Maury; P. Dulski; S. Fourcade; M. Bohn; R. Brousse

1995-01-01

291

Rare earth elements in stream waters from the Rokko granite area, Japan: Effect of weathering degree of watershed rocks  

Microsoft Academic Search

The concentrations of major elements and rare earth elements (REE) of the stream waters from the Rokko granite area, Japan, were analyzed to examine the relationship between the degree of weathering and chemistry of the waters. The clay minerals in the related soils from the watershed areas were also examined. It was found that the relative proportion of kaolinite to

TAIGA NAKAJIMA; YASUTAKA TERAKADO

292

Rare earth and trace element geochemistry of termite mounds in central and northeastern Namibia: Mechanisms for micro-nutrient accumulation  

Microsoft Academic Search

Rare earth element (REE) and trace element concentrations of ten termite mounds and adjacent topsoil from central and northeastern Namibia were used to investigate the processes underlying the alteration of soil chemical and physical properties by termites (Macrotermes spp.). Accumulation of micro-nutrients in the mounds was of particular interest because of the ecological implications of the enhanced availability of these

Aboubakar Sako; Anthony J. Mills; Alakendra N. Roychoudhury

2009-01-01

293

Major element fractionation in chondrites by distillation in the accretion disk of a T Tauri Sun?  

NASA Astrophysics Data System (ADS)

Redistribution or loss of batches of condensate from a cooling protosolar nebula is generally thought to have led to the formation of the chemical groups of chondrites. This demands a nebula hot enough for silicate vaporization over 1-3 AU, the region where chondrites formed. Alternatively, heating of a protosolar accretion disk may have been confined to an annular zone at its inner edge, about 0.06 AU from the protosun. Most infalling matter was accreted by the protosun, but a proportion was heated and carried outwards by an x-wind. Shu et al. (1996; 1997) proposed that larger objects such as chondrules and Ca-, Al-rich inclusions (CAIs) were returned to the disk at asteroidal distances by sedimentation from the x-wind. Fine dust and gas were lost to space. The model implies that solids were not lost from the cold disk. The chemical compositions of the chondrite groups were produced by mixing different proportions of CAIs and chondrules with disk solids of CI composition. Heating at the inner edge of the disk was accompanied by particle irradiation, which synthesized nuclides including 26Al. The x-wind model can produce CAIs, not chondrules, and allows survival of presolar grains >0.06 AU from the protosun. Normalization to Al and CI indicates that non-carbonaceous chondrites (CCs) may be disk material that gained a Si- and Mg-enriched fraction. CCs are different; they appear to be CI that lost lithophile elements more volatile than Ca. Five CC groups also lost Ni and Fe but the CH group gained siderophiles. Elemental loss from CI is incompatible with the x-wind model. Silicon and CI normalization confirms that the CM, CO, CK and CV groups may be CI that gained refractories as CAIs. The Si-, Mg-rich fraction may have formed by selective vaporization followed by precipitation on grains in the x-wind. This fractional distillation mechanism can account for lithophile element abundances in non-CC groups, but an additional process is required for the loss of Ca and Mn in the EL group and for fractionated siderophile abundances in the H, L and LL groups. Heated and recycled fractions were not homogenized across the disk so the chondrite groups were established in a single cycle of enhanced protosolar activity in <104 yr, the time for a mm-sized particle to drift into the Sun from 2-3 AU, due to gas-drag.

Hutchison, Robert

2002-01-01

294

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

NASA Astrophysics Data System (ADS)

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

Kulaks?z, Serkan; Bau, Michael

2007-08-01

295

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

NASA Astrophysics Data System (ADS)

Past workers have used rare-earth element patterns recorded in biogenic apatite as proxies for original seawater chemistry. To explore the potency of this approach, we analyzed Pennsylvanian conodonts from limestones, gray shales, and black shales of the Fort Scott and Pawnee formations (Desmoinesian) and Swope and Dennis formations (Missourian) in Kansas, Missouri, and Iowa, U.S.A. Analysis of individual platform conodonts from seven taxa using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) revealed a consistent enrichment in the middle rare-earth elements (MREE). Analogous MREE enrichment has been observed in authigenic apatite and bulk samples of phosphate-rich black shales from the same formations. Importantly, however, phosphate-depleted shales intimately associated with the P-rich intervals are relatively depleted in MREE. These antithetic patterns argue convincingly for secondary migration from the bulk sediment into the phosphate, and the extent of MREE enrichment in the conodonts is correlated positively with the total REE content. MREE enrichment in conodonts does not vary systematically as a function of lithology, stratigraphic level, conodont genus, geographic location, or with independent estimates of paleoredox conditions in the bottom waters. Collectively, these results argue for postmortem (diagenetic) REE uptake resulting in a pronounced (and progressive) MREE enrichment. Any cerium anomalies, if initially present, were masked by diagenetic uptake of REE. Paleoenvironmental interpretations of conodont REE, particularly for samples exhibiting MREE enrichment, should therefore be viewed with caution.

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

2009-03-01

296

Effect of mixing three rare-earth elements on the superconducting properties of ?  

NASA Astrophysics Data System (ADS)

We report the effect of mixing three rare-earth (RE) elements in the RE site on the superconducting properties of melt-processed 0953-2048/10/9/006/img10, in which RE elements are selected from the group of Nd, Sm, Eu and Gd. The heat treatment profiles for melt processing were determined according to the peritectic decomposition temperatures obtained from the thermal analysis measurements. Microstructural observations and compositional analysis showed that the main phase was (0953-2048/10/9/006/img11, in which the ratio of three RE elements (R1, R2, R3) was equal to that of the nominal composition, indicating that mixing of RE elements was uniform. All the samples showed relatively high 0953-2048/10/9/006/img12 in the range 93.1 - 95.3 K and exhibited the secondary peak effect in the magnetization curves at 77 K with the irreversibility field higher than that of melt-processed Y - Ba - Cu - O. A high 0953-2048/10/9/006/img13 value of 0953-2048/10/9/006/img14 at 77 K and 2 T was achieved in (Nd, Eu, Gd)0953-2048/10/9/006/img15 for field parallel to the c-axis.

Muralidhar, M.; Chauhan, H. S.; Saitoh, T.; Kamada, K.; Segawa, K.; Murakami, M.

1997-09-01

297

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

NASA Astrophysics Data System (ADS)

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.

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

2006-03-01

298

Earth  

NSDL National Science Digital Library

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

299

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

300

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

PubMed

In this work, the elemental content (C, N, H, S, O), the organic matter content and the calorific value of various organic components that are commonly found in the municipal solid waste stream were measured. The objective of this work was to develop an empirical equation to describe the calorific value of the organic fraction of municipal solid waste as a function of its elemental composition. The MSW components were grouped into paper wastes, food wastes, yard wastes and plastics. Sample sizes ranged from 0.2 to 0.5 kg. In addition to the above individual components, commingled municipal solid wastes were sampled from a bio-drying facility located in Crete (sample sizes ranged from 8 to 15 kg) and were analyzed for the same parameters. Based on the results of this work, an improved empirical model was developed that revealed that carbon, hydrogen and oxygen were the only statistically significant predictors of calorific value. Total organic carbon was statistically similar to total carbon for most materials in this work. The carbon to organic matter ratio of 26 municipal solid waste substrates and of 18 organic composts varied from 0.40 to 0.99. An approximate chemical empirical formula calculated for the organic fraction of commingled municipal solid wastes was C(32)NH(55)O(16). PMID:22119517

Komilis, Dimitrios; Evangelou, Alexandros; Giannakis, Georgios; Lymperis, Constantinos

2011-11-26

301

Modeling of the lung impedance using a fractional-order ladder network with constant phase elements.  

PubMed

The self similar branching arrangement of the airways makes the respiratory system an ideal candidate for the application of fractional calculus theory. The fractal geometry is typically characterized by a recurrent structure. This study investigates the identification of a model for the respiratory tree by means of its electrical equivalent based on intrinsic morphology. Measurements were obtained from seven volunteers, in terms of their respiratory impedance by means of its complex representation for frequencies below 5 Hz. A parametric modeling is then applied to the complex valued data points. Since at low-frequency range the inertance is negligible, each airway branch is modeled by using gamma cell resistance and capacitance, the latter having a fractional-order constant phase element (CPE), which is identified from measurements. In addition, the complex impedance is also approximated by means of a model consisting of a lumped series resistance and a lumped fractional-order capacitance. The results reveal that both models characterize the data well, whereas the averaged CPE values are supraunitary and subunitary for the ladder network and the lumped model, respectively. PMID:23850980

Ionescu, C M; Machado, J A T; De Keyser, R

2011-02-01

302

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

303

Rare earth element compositions of core sediments from the shelf of the South Sea, Korea: Their controls and origins  

NASA Astrophysics Data System (ADS)

Rare earth elements (REEs) of bulk sediments and heavy mineral samples of core sediments from the South Sea shelf, Korea, were analyzed to determine the constraints on REE concentrations and distribution patterns as well as to investigate their potential applicability for discriminating sediment provenance. Bulk sediment REEs showed large variation in concentrations and distribution patterns primarily due to grain size and carbonate dilution effects, as well as due to an abundance of heavy minerals. In the fine sandy sediments (cores EZ02-15 and 19), in particular, heavy minerals (primarily monazite and titanite/sphene) largely influenced REE compositions. Upper continental crust-normalized REE patterns of these sand-dominated sediments are characterized by enriched light REEs (LREEs), because of inclusion of heavy minerals with very high concentrations in LREEs. Notably, such a strong LREE enrichment is also observed in Korean river sediments. So, a great care must be taken when using the REE concentrations and distribution patterns of sandy and coarse silty shelf sediments as a proxy for discriminating sediment provenance. In the fine-grained muddy sediments with low heavy mineral abundance, in contrast, REE fractionation ratios and their UCC-normalized patterns seem to be reliable proxies for assessing sediment provenance. The resultant sediment origin suggested a long lateral transportation of some fine-grained Chinese river sediments (probably the Changjiang River) to the South Sea of Korea across the shelf of the northern East China Sea.

Jung, Hoi-Soo; Lim, Dhongil; Choi, Jin-Yong; Yoo, Hae-Soo; Rho, Kyung-Chan; Lee, Hyun-Bok

2012-10-01

304

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

2012-06-28

305

Geochemistry and biogeochemistry of rare earth elements in a surface environment (soil and plant) in South China  

NASA Astrophysics Data System (ADS)

Plants and soils derived from different kinds of parent materials in South China were collected for analyses of rare earth elements (REEs) by inductively coupled plasma-mass spectrometry (ICP-MS). The distribution patterns and transportation characteristics of REEs in the soil-plant system were studied. The results show that geochemical characteristics of REEs depend on the types of soils, soils derived from granite being the highest in REE concentration. In a soil profile, REE concentrations are higher in B and C horizons than those in A horizon, with Eu negative anomaly and Ce positive anomaly. Plants of different genera growing in the same sampling site have quite similar REE distribution pattern, but plants of the same genera growing in different soils show considerable variation in characteristics of REEs. The patterns of the different parts of plant resemble each other, but the slope of the patterns becomes different. REEs have fractionated when they were transported and migrated from soil to plant root, stem and leaf, revealing that heavy REEs are relatively less available. REEs distributions in plants are influenced by the soil they grow in and also characterized by their individual biogeochemical characteristics. Biological absorption coefficients indicate difference of REE absorption capacity of plants.

Miao, Li; Xu, Ruisong; Ma, Yueliang; Zhu, Zhaoyu; Wang, Jie; Cai, Rui; Chen, Yu

2008-11-01

306

Rare earth element geochemistry of the Scourian complex N.W. Scotland — Evidence for the granite-granulite link  

Microsoft Academic Search

Medium-to high-pressure granulite facies complexes represent samples of lower crustal material and are, therefore, important in the study of crustal processes. New rare earth element data for the Scourian granulite facies terrain of the Precambrian Lewisian complex of N.W. Scotland indicate that:1.Overall, the Scourian complex has a light rare earth enriched pattern with a small but distinct positive Eu anomaly;2.While

C. Pride; G. K. Muecke

1980-01-01

307

Finite element analysis of the magnetic field in rare-earth permanent magnet systems, with consideration of temperature dependence  

Microsoft Academic Search

A finite element method for the solution of the electromagnetic field taking account of the temperature properties of rare-earth magnets is presented. The nonuniform distribution of magnetization caused by the temperature-dependent properties of rare-earth permanent magnets is considered, and both reversible and irreversible changes in the magnetic strength of magnets with temperature are investigated. An analysis of the thermoelectromagnetic coupled

S. Chen; K. J. Binns; Z. Liu; D. W. Shimmin

1992-01-01

308

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

Microsoft Academic Search

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

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

1995-01-01

309

Inter-element fractionation of highly siderophile elements in the Tonga Arc due to flux melting of a depleted source  

NASA Astrophysics Data System (ADS)

Highly siderophile element concentrations (HSEs: Os, Ir, Ru, Pt, Pd, and Re) have been determined for a suite of fresh, submarine mafic lavas from the northern Tonga Arc front and the nascent backarc Fonualei Spreading Centre (FSC). Prior melt depletion of the Tongan mantle wedge combined with a high degree of fluid fluxed melting is thought to have produced boninitic magmas at several arc and FSC locations. As such, this arc system provides an opportunity to assess the fluid mobility of HSEs and to investigate the effects of fluid-induced melting and prior melt depletion on HSE behaviour during both mantle melting and magma evolution. Tongan lavas display extreme enrichment of Pt (2.5-32 ng/g) and Pd over Os (0.002-0.6 ng/g), Ir, and Ru, significantly greater than basalts from mid-ocean ridges. Magma evolution increases the degree of fractionation, resulting in the highest recorded Pt/Ru ratios (>300) in arc front samples with MgO <8 wt.%. This increasing fractionation is due to the mild incompatibility of Pt and Pd, and concurrent compatibility of Ru, during sulphide undersaturated magma evolution. However, the fractionation of Pt and Pd from Os, Ir, and Ru is observed in the highest MgO samples, indicating source inheritance. Prior melt depletion of the mantle and elevated oxygen fugacity both increase the likelihood of complete consumption of sulphide in the source during melting, which typically leads to melts with high concentrations of all the HSE. Indeed, modelling indicates that 25% aggregate partial melting of a depleted MORB-mantle source, proposed for the Tonga Arc, will lead to complete base-metal sulphide consumption unless there is considerable addition of S by the slab flux (at least 200 ?g/g). Although source enrichment of Pt, Pd, and Re by slab fluids may take place, the fractionation of Pt and Pd from Os, Ir, and Ru can largely be explained by relatively low-temperature, yet high-degree, melting of fluid-fluxed melt-depleted mantle. The high Pt and Pd contents can be produced by the exhaustion of sulphide in the source, while the presence of Ru-Os-(Ir) alloys or sulphides (e.g. laurite) associated with Cr-spinel can explain Os, Ir, and Ru retention in the source residue. Such phases have been documented in fluid-fluxed sub-arc mantle from ophiolites. Osmium isotopes co-vary negatively with Os abundance and thus appear to be dominated by shallow level contamination. The most Os-rich samples, however, have 187Os/188Os ratios (0.126-0.132) which are typical of DMM and MORB, suggesting an indistinguishable flux of radiogenic Os from the slab. The significant fractionation of Pt and Re from Os in arc settings will lead, over time, to elevated 186Os and 187Os which may be relevant to the observed enrichments of these isotopes in some mantle regions. In addition, the differing behaviour of Ru and Ir, and the implication of a mantle source containing Ru-rich microphases, may have consequences for the estimation of the HSE composition of primitive upper mantle.

Dale, Christopher W.; Macpherson, Colin G.; Pearson, D. Graham; Hammond, Samantha J.; Arculus, Richard J.

2012-07-01

310

Sequential separation of the yttrium—heavy rare earths by fractional hydroxide precipitation  

Microsoft Academic Search

In the course of the treatment of monazite in Brazil a fraction of crude yttrium carbonate is obtained. The main constituents of this fraction are: Y2O3 (76.7%), Dy2O3 (9.31%), Er2O3 (3.21%), Yb2O3 (2.34%), Lu2O3 (1.56%), Ho2O3 (1.40%), Tb4O7 (0.97%), Gd2O3 (0.69%), CeO2 (0.43%), Tm2O3 (0.33%), Nd2O3 (0.22%), La2O3 (0.21%), Sm2O3 (0.14%), Pr6O11 (0.13%), and minor impurities like nickel, calcium, and

Mari E. de Vasconcellos; Carlos A. da S. Queiroz; Alc??dio Abrão

2004-01-01

311

Fractionation of volatile elements in the early solar system: evidence from heating experiments on primitive meteorites  

NASA Astrophysics Data System (ADS)

Compared to the average composition of the solar nebula (as determined by solar photospheric abundances), most meteorites and planets are depleted in volatile elements. The only exceptions are CI chondrites and perhaps interstellar dust particles and comets. The depletion of volatile elements is one of the most important fractionation processes that has affected solid matter in the early solar system. Loss of volatile elements may have occurred either by evaporation during heating of material of solar composition or by incomplete condensation in the early solar nebula. To test the evaporation hypothesis heating experiments on chunks of the Allende CV3 chondrite were performed under controlled oxygen fugacities ( fO 2), from air to log fO 2 = -16.5, and at temperatures ranging from 1050 to 1300°C. After removal from the furnace, residues were analyzed by instrumental neutron activation analysis, spark source mass spectrometry and with a C,S analyzer. Experiments in closed quartz vials, with solid fO 2 buffers (Fe?FeO, etc.), were found to be problematic because of strong preference of quartz for alkalis and Ga. Most experments were therefore made in an open system with fO 2 controlled by CO?CO 2 gas mixing. The volatile element pattern of heated samples from the Murchison CM meteorite is very similar to that of heated Allende. Since Murchison and Allende are different in chemical composition (in particular in volatile element contents), texture and mineralogy, the results of the heating experiments do not strongly depend upon these parameters. Most experiments were therefore confined to Allende. The results show for most elements a strong dependence of apparent volatilities on fO 2. The elements Os, Re, Au and As are stable at reducing (low fO 2) and volatile under oxidizing conditions (high fO 2). The transition occurs for Re, Au and As between the Fe?FeO and Ni?NiO buffers. Volatilization of Os requires oxygen fugacities several orders of magnitude above Ni?NiO. Alkali elements (Na, K), Cu, Ga and Zn show the apposite behavior, losses in experiments at reducing and retention at oxidizing conditions. The element Mn shows no depletion, even in the 1300°C experiments, while the major fraction of Se is lost in all experiments, reflecting loss of sulfide, which is confirmed by the results of S analyses. Lead was found to be similarly volatile to Se and S. Since the host phases of most of the volatile elements are similar in CM, CV and ordinary chondrites, the results obtained in the present study should be applicable to carbonaceous and ordinary chondrites. Metamorphism at temperatures above 1050°C and at oxygen fugacities above the Fe?FeO buffer would thus lead to large losses of Au, As and Re, which is observed neither in carbonaceous nor in ordinary chondrites. Ratios of volatile to non-volatile metals, e.g. Au/Ir, As/Ir and Re/Ir ratios, are "normal" in these meteorites (i.e. minor depletion in Au and As and chondritic Re/Ir ratios). Apparently, carbonaceous and ordinary chondrites were never exposed to such conditions. The strong depletion of Ga and Zn in experiments at low oxygen fugacities excludes metamorphism of chondritic meteorites under these conditions. This is confirmed by earlier results of Matza, S. D. and Lipschutz, M. E. ( Proc. 8th Lunar Sci. Conf., pp. 161-176, 1977), who found that in reducing conditions losses of Zn are observed at temperatures as low as 700°C and Ga losses at 900°C. A detailed comparison of the volatile element patterns in residues of heating experiments with volatile element patterns of CV3 meteorites shows that samples produced during heating at the IW buffer (iron-wüstite buffer) have volatile element patterns approximately resembling the CV3 pattern, although there are still significant differences, making the origin of such patterns by thermal metamorphism of CI material unlikely. Additional arguments are presented suggesting that heating of meteoritic material to produce fractionated volatile element patterns is unlikely.

Wulf, A. V.; Palme, H.; Jochum, K. P.

1995-02-01

312

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

PubMed

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

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

2013-07-03

313

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

Microsoft Academic Search

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

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

2003-01-01

314

Rare earth elements in Ca-phosphates of Allende carbonaceous chondrite  

SciTech Connect

The Ca-phosphate phases in the Allende CV3 meteorite were selectively dissolved in ammoniacal EDTA solution and measured for abundances of the rare earth elements (REE) by radiochemical neutron activation and mass-spectrometric isotope dilution analyses. The REE abundances in CA-phosphates of Allende are remarkably different from those of ordinary chondrites. All the REE except Eu were observed to be enriched by factors of 50-100 relative to the Cl values. This is 3-4 times lower than concentrations of REE in the ordinary-chondrite phosphates. Allende phosphates have a small positive Eu anomaly, in contrast to the large negative Eu anomaly in phosphates from ordinary chondrites. Though the positive Eu anomaly in Allende Ca-phosphates is puzzling, the lack of a negative Eu anomaly in Allende Ca-phosphates suggests that they never have been in equilibrium with Allende coarse-grained Ca, Al-rich inclusions or their precursor materials. 42 references.

Ebihara, M.; Honda, M.

1987-09-01

315

New autoionizing states near the first ionization limit of rare earth element Dy  

NASA Astrophysics Data System (ADS)

This paper describes the investigation of autoionizing states near the first ionization limit of rare-earth element Dy. The 62, 51, 97 and 25 new autoionizing states resulting from the states of 4f10(5I8)6s6p(3P20) 3I70, 4f9(6H0)5d2(3F) (8G0)6s9G70, 4f9(6F0)5d6s2 7H70 and 4f95d6s2 7K70, respectively, were found by using a laser resonance ionization time-of-flight mass spectrometer (LRI-TOFMS). The photoionization efficiencies for different channels were compared with each other. In addition, the Shore-Fano parameters of autoionizing states were determined by a nonlinear fitting program.

Hai-jun, Zhou; Xiang-yuan, Xu; Wen, Huang; Die-yan, Chen

1993-12-01

316

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

317

Thermochemical treatment of zeolitic cracking catalysts containing rare-earth elements  

SciTech Connect

The authors report on the optimization of process conditions in the thermochemical treatment in commercial production of the catalyst KMTsR-N. Freshly molded zeolitic hydrogel beads, with or without specially introduced aluminum hydroxide, were treated successively with a nitrate solution of rare-earth elements (REE) and an ammonium nitrate solution. A simplified flow plan for the thermochemical treatment is shown. The dynamics of the variation and concentration of the treating solutions and the composition of the hydrogen beads during thermochemical treatment is shown. The studies show that in order to obtain a uniform distribution of REE cations in zeolitic aluminosilicate hydrogel beads, the beads must be treated with a solution containing a mixture of ammonium and REE cations.

Baiburskii, V.L.; Kosolapova, A.P.; Rabinovich, S.I.; Bol'shakova, T.A.

1987-01-01

318

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

PubMed

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

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

2010-10-19

319

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

NASA Astrophysics Data System (ADS)

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

Webb, Gregory E.; Kamber, Balz S.

2000-05-01

320

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

SciTech Connect

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

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

1988-08-01

321

Rare earth element and stable isotope (O, S) geochemistry of barite from the Bijgan deposit, Markazi Province, Iran  

NASA Astrophysics Data System (ADS)

The Bijgan barite deposit, which is located northeast of Delijan in Markazi Province of Iran, occurs as a small lenticular body at the uppermost part of an Eocene volcano-sedimentary rock unit. The presence of fossiliferous and carbonaceous strata suggests that the host rocks were deposited in a quiet marine sedimentary environment. Barite, calcite, iron oxides and carbonaceous clay materials are found as massive patches as well as thin layers in the deposit. Barite is marked by very low concentrations of Sr (1-2%) and total amounts of rare earth elements (REEs) (6.25-17.39 ppm). Chondrite-normalized REE patterns of barite indicate a fractionation of light REEs (LREEs) from La to Sm, similar to those for barite of different origins from elsewhere. The LaCN/LuCN ratios and chondrite-normalized REE patterns reveal that barite in the Bijgan deposit is enriched in LREE relative to heavy rare earth elements (HREEs). The similarity between the Ce/La ratios in the barite samples and those found in deep-sea barite supports a marine origin for barite. Lanthanum and Gd exhibit positive anomalies, which are common features of marine chemical sediments. Cerium shows a negative anomaly in most samples that was inherited from the negative Ce anomaly of hydrothermal fluid that mixed with seawater at the time of barite precipitation. The ?18O values of barites show a narrow range of 9.1-11.4‰, which is close to or slightly lower than that of contemporaneous seawater at the end of the Eocene. This suggests a contribution of oxygen from seawater in the barite-forming solution. The ?34S values of barites (9.5-15.3‰) are lower than that of contemporaneous seawater, which suggests a contribution of magmatic sulfur to the ore-forming solution. The oxygen and sulfur isotope ratios indicate that submarine hydrothermal vent fluids are a good analog for solutions that precipitated barite, due to similarities in the isotopic composition of the sulfates. The available data including tectonic setting, host rock characteristics, REE geochemistry, and oxygen and sulfur isotopic compositions support a submarine hydrothermal origin for the Bijgan barite deposit. At the seafloor, barite deposition occurred where ascending Ba-bearing hydrothermal fluids encountered seawater. Sulfate was derived from the sulfate-bearing marine waters, and, to a lesser extent, by oxidized H2S, which was derived from magmatic hydrothermal fluids.

Ehya, Farhad

2012-01-01

322

The geochemical characteristics of aqueous rare-earth elements in shallow karst groundwater in Guiyang City, China  

Microsoft Academic Search

Fifty-seven shallow groundwater samples were collected from Guiyang karst basin, China, to analyze the aqueous rare-earth\\u000a elements in low-water seasons and it is shown that the total amount of rare-earth elements (?REE) in karst groundwater is\\u000a exceedingly low compared with that in carbonate rocks or weathering crusts of carbonate rocks, and ranges from 0.01 to 0.43,\\u000a from 0.03 to 0.27,

Shouyang He; Lijun Zhu; Ruidong Yang; Zheng Shen; Xiaohong Yu

2011-01-01

323

Tracing irradiation-induced defect state of monazite by photoluminescence of rare Earth elements  

NASA Astrophysics Data System (ADS)

Natural monazite is known in contrast to zircon, to almost never be found in the metamict state (Ewing, 1975) despite the fact that it received intensive radiation doses during geologic history by U and Th incorporation. Radiation damages in natural monazite seems to be limited to isolated domains within the crystal (Meldrum et al., 1998). Such property controlled the fact that the monazite lattice is easily healed even at low temperature as it was shown by TEM, XRD and Raman spectrometry (Seydoux-Guillaume et al., 2002). In order to estimate the degree of disorder and the healing of defects we used trivalent neodymium as an internal luminescent probe (Gaft et al., 2001). As a matter of fact the radiative electronic transitions of rare earth elements are very sensible to the short-range crystallographic order around them. Three natural monazites thermally untreated and quenched at 450, 500, 700, 800 and 1000^oC were analyzed under 514 nm Argon laser excitation with a Renishaw microspectrometer. Nd3+ emission was recorded in the range of 750 nm to 1 ?m. The ^4F3/2 rightarrow ^4I9/2 transition parameters (position and width) show that 1) the position of the Stark levels do not change during thermal treatment, and 2) that the emission line widths decrease continuously (from 25 to 37%) from room temperature to 1000^oC. These results indicates that before annealing, sub sites of Nd were present with slight different environments induced by internal irradiation induced displacement of ions around them (short range disorder). After thermal treatment a continuous reorganization of the lattice occurs up to 1000^oC with quite strong rearrangement of the environment around the rare-earth leading to a decrease of the Nd sub site number. Thus, the luminescent probe reveals that defect healing continue at much higher temperatures than what was previously reported indicating that luminescence is a very sensible tool to appreciate the degree of disorder in mineral phases. Gaft M., Panczer G., Reisfeld R. &Uspensky E. (2001) Laser-induced time-resolved luminescence as a tool for rare-earth element identification in minerals., Phys. Chem. Minerals, 28, 347-363.

Panczer, G.; Seydoux-Guillaume, A. M.; Montel, J. M.; Champagnon, B.

2003-04-01

324

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

SciTech Connect

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

Perl, M.

2000-01-12

325

A Modified Streamline-Fractional-Step Finite Element Method for Solving Unsteady Incompressible Viscous Flow  

NASA Astrophysics Data System (ADS)

This paper proposes a numerical method for computing the flows at high Reynolds number (Re). A modified fractional step (FS) finite element method (FEM) is based upon the velocity correction method (VCM) and uses two concepts to conduct intermediate velocity. The first is the streamline method, which provides an accurate multidimensional generalization, and the second is the balancing tensor diffusivity (BTD), which is used as the artificial diffusion for the stabilization techniques. The accuracy of this method for the advection-diffusion equation is demonstrated for the rotating cone problem. The unsteady incompressible viscous flows, such as square cavity flow at Re?10000 and flow past a cylinder at Re?2000, are simulated without any numerical instability.

Morinaga, Eiji

326

Carbon and other light element contents in the Earth's core based on first-principles molecular dynamics.  

PubMed

Carbon (C) is one of the candidate light elements proposed to account for the density deficit of the Earth's core. In addition, C significantly affects siderophile and chalcophile element partitioning between metal and silicate and thus the distribution of these elements in the Earth's core and mantle. Derivation of the accretion and core-mantle segregation history of the Earth requires, therefore, an accurate knowledge of the C abundance in the Earth's core. Previous estimates of the C content of the core differ by a factor of ?20 due to differences in assumptions and methods, and because the metal-silicate partition coefficient of C was previously unknown. Here we use two-phase first-principles molecular dynamics to derive this partition coefficient of C between liquid iron and silicate melt. We calculate a value of 9 ± 3 at 3,200 K and 40 GPa. Using this partition coefficient and the most recent estimates of bulk Earth or mantle C contents, we infer that the Earth's core contains 0.1-0.7 wt% of C. Carbon thus plays a moderate role in the density deficit of the core and in the distribution of siderophile and chalcophile elements during core-mantle segregation processes. The partition coefficients of nitrogen (N), hydrogen, helium, phosphorus, magnesium, oxygen, and silicon are also inferred and found to be in close agreement with experiments and other geochemical constraints. Contents of these elements in the core derived from applying these partition coefficients match those derived by using the cosmochemical volatility curve and geochemical mass balance arguments. N is an exception, indicating its retention in a mantle phase instead of in the core. PMID:23150591

Zhang, Yigang; Yin, Qing-Zhu

2012-11-13

327

A mathematical model of trace element and isotopic behavior during simultaneous assimilation and imperfect fractional crystallization  

NASA Astrophysics Data System (ADS)

The process of coupled assimilation and fractional crystallization (AFC) is one of the most popular petrogenetic concepts that explains magmatic differentiation. Conventional geochemical models for this process assume that crystals are removed instantaneously from the magma body as they are produced; however, recent advances in isotopic microanalysis have clarified that the crystals are suspended within the magma body for a certain period, affecting the whole-rock composition in response to the intra-grain isotopic zoning. This study develops a mass balance model for simultaneous assimilation and imperfect fractional crystallization (AIFC) to describe the effects of suspended crystals on the path of magma evolution. The mass balance differential equations for the liquid and suspended crystals are solved simultaneously. The analytical solution of the AIFC equations gives a quantitative account of the evolution paths of trace elements and isotopes within bulk crystals, liquid, and magma (crystals plus liquid). The chemical path of the magma differs markedly from that predicted by the conventional AFC model.

Nishimura, Koshi

2012-09-01

328

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

329

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

330

Shoshonitic volcanism in the Northern Mariana Arc: 2. Large-ion lithophile and rare earth element abundances: Evidence for the source of incompatible element enrichments in intraoceanic arcs  

NASA Astrophysics Data System (ADS)

The Mariana-Volcano-Izu arc system extends 2400 km north to south and is an outstanding example of an intraoceanic magmatic arc. In spite of this, the system is poorly known because most of it is submarine. Volcanism is entirely submarine in the northernmost Mariana arc, between 20°40' and 24°N. This is the Northern Seamount Province (NSP) and was the focus of a detailed marine geologic and geochemical study, with additional data drawn from adjacent arc segments to the north (Volcano arc) and south (Central Island Province (CIP) of the Mariana arc). Samples from 24 submarine volcanoes and three islands were analyzed for concentrations of K, Rb, Sr, Ba, and the rare earth elements (REE). These data show strong variations along the arc, being relatively depleted in the more mature, tholeiitic and low-K calc-alkaline volcanoes of the Volcano arc and the Mariana CIP, containing on average 6100 ppm K, 300 ppm Sr, 200 ppm Ba, and 6 ppm La. All of the NSP is enriched in large ion lithophile (LIL) and light rare earth elements (REE), particularly the northern half (26,000 ppm K, 700 ppm Sr, 900 ppm Ba, 47 ppm La); these lavas have strong shoshonitic affinities. These enrichments do not result from fractional crystallization of CIP-type melts. The source responsible for these enrichments shares some features in common with Mariana CIP and Volcano arc sources: K/Rb and K/Ba in particular are similar (˜500 and ˜30, respectively). However, Ba/La, Sr/Nd, and (Ce/Yb)n change drastically, with Ba/La and Sr/Nd decreasing to mantle values with increasing LIL and LREE enrichment. The origin of the LIL and LREE enrichments in the NSP shoshonites does not result from variations in the behavior or composition of the subducted lithosphere. Melting occurs exclusively within the mantle wedge, and forward modeling of the REE patterns for all Mariana and Volcano arc lavas indicates that melt generation occurs within the stability field of spinel lherzolite, probably within the upper 40-50 km of the subarc asthenosphere. Lavas from the large volcanoes of the Mariana CIP and Volcano arc result from 10-20% melting of spinel lherzolite, followed by varying amounts of low-P fractional crystallization. Inferences based on REE forward models that the NSP shoshonites manifest very low (1%) degrees of partial melting of LIL- and LREE-enriched spinel lherzolite are inconsistent with observed similar concentrations in tholeiites and shoshonites of high field strength cations such as TiO2 and Yb. Some of this inconsistency can be explained as resulting from source or melt mixing, with the NSP shoshonites being derived from a LIL- and LREE-enriched source or melt, with Ba/La and La/Yb indistinguishable from that of ocean island basalts (OIB), while Mariana CIP and Volcano arc melts are derived from a depleted mild-ocean ridge basalt-like mantle that has been recharged with K, Rb, Sr, and Ba by hydrous fluids. These variations are interpreted as reflecting the evolution of the subarc asthenosphere, with a depletion in time resulting from the continuous extraction of basaltic melts.

Lin, Ping-Nan; Stern, Robert J.; Bloomer, Sherman H.

1989-04-01

331

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

332

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

333

Determination of rare-earth elements in rock samples by an improved high-performance ion chromatography  

Microsoft Academic Search

An analytical technique of rare-earth elements (REE) in rock samples using a high-performance ion chromatography (HPIC) is described. The REE in rock samples were separated from other elements using a conventional ion-exchange column, and then measured by the HPIC. ? -hydroxyisobutyric acid and Arsenazo III were used for eluants and a post-column reagent for the HPIC, respectively. The use of

TSUYOSHI ISHIKAWA; KENJI SUGIMOTO; KAZUYA NAGAISHI

334

The properties of Sn9Zn lead-free solder alloys doped with trace rare earth elements  

Microsoft Academic Search

The Sn-Zn alloys have been considered as lead-free solders. It is well known that their poor properties of wetting and oxidation\\u000a resistance are the main problems to prevent them from becoming commercially viable solders. In this paper, trace rare earth\\u000a (RE) elements of mainly Ce and La have been used as alloying elements into the Sn-9Zn alloy. The results indicated

C. M. L. Wu; D. Q. Yu; C. M. T. Law; L. Wang

2002-01-01

335

Determination of rare earth elements in geological materials by inductively coupled argon plasma\\/atomic emission spectrometry  

Microsoft Academic Search

Inductively coupled argon plasma\\/optical emission spectrometry (ICAP\\/OES) is useful as a simultaneous, multielement analytical technique for the determination of trace elements in geological materials. A method for the determination of trace-level rare earth elements (REE) in geological materials using an ICAP 63-channel emission spectrometer is described. Separation and preconcentration of the REE and yttrium from a sample digest are achieved

J. G. Crock; F. E. Lichte

1982-01-01

336

High-resolution records of location and stratigraphic provenance from the rare earth element composition of fossil bones  

Microsoft Academic Search

Bone apatite acts as a natural, timed sampling device, scavenging trace elements from local pore waters over timescales of ca. 1–50ka. The rare earth element (REE) and U\\/Th composition of fossil bones reflects associated pore water compositions during the period of recrystallisation. The REE composition of fossil bones is controlled by partitioning of REE between pore waters and particle surfaces,

C. N. Trueman; A. K. Behrensmeyer; R. Potts; N. Tuross

2006-01-01

337

Linking rare earth element zoning in major and accessory minerals to better understand metasedimentary migmatites  

NASA Astrophysics Data System (ADS)

Trace element signatures from major and accessory minerals are increasingly used to place constraints on the ages of tectonothermal events and gain insights into processes operating in the deep continental crust. Minerals such as garnet, zircon or monazite represent sensitive recorders of events if a solid understanding exists of what trace element signatures represent. A study underway on granulite facies migmatites is providing insights into trace element signatures in garnet, and when integrated with in situ, microbeam analysis of zircon and monazite, is allowing a complex polymetamorphic history to be deciphered. The Larsemann Hills, east Antarctica, are composed of felsic orthogneisses and metasediments that were affected by high-grade metamorphism and partial melting at c. 7 kbar and >800 °C. Initially interpreted to have experienced a single cycle of metamorphism at c. 550-530 Ma, recent ages suggest that the area was affected by an earlier high-grade event at c. 900 Ma; the timing of migmatization relative to these two events remains uncertain. To address this, a detailed study has targeted metasedimentary migmatites. Garnet, zircon and monazite were analysed from melanosome, leucosome and selvage domains. Garnet (predominantly almandine-pyrope) preserves little, if any, major element zoning. In contrast, it records systematic within-grain variations in heavy rare earth element (HREE) concentration depending on textural context. Garnet within residuum domains displays broad cores with flat HREE slopes in chondrite-normalized plots, but are HREE-depleted (negative slopes) at boundaries adjacent to leucosome. In contrast, garnet boundaries adjacent to cordierite-rich selvages are typically HREE-enriched, with positive-sloping patterns. It is interpreted that core-rim depletions in HREE may reflect evolution of the whole-rock reservoir towards depletion during migmatization and garnet growth. Enrichment in garnet HREE adjacent to selvage domains likely resulted from local reaction between solids and melts either during melt transit and/or crystallization. Monazite, which is preferentially located in leucosome domains, preserves ages that reflect growth at c. 900 Ma and c. 530 Ma, although trace element signatures are ambiguous. However, zircon, which is preferentially located in selvage domains, preserves c. 530 Ma rims with depleted, flat to negatively sloping HREE patterns. It is interpreted that these zircon rims grew in, or near to equilibrium with garnet cores and rims during partial melting, and may date at least part of migmatite formation in the Larsemann Hills. They do not date the final crystallization of melts and development of selvage domains. Preliminary results of this study have shown that the trace element composition of garnet from high-temperature terrains can be a powerful tool in tracking metamorphic and melting processes where major elements zoning is no longer preserved. This study also demonstrates the utility of textural context when interpreting trace element patterns and ages from dateable accessory minerals in rocks from polycyclic metamorphic terrains.

Matthews, J. A.; Kelly, N. M.; Koenig, A.; Harley, S. L.

2011-12-01

338

Rare earth element trends and cerium-uranium-manganese associations in weathered rock from Koongarra, Northern Territory, Australia  

Microsoft Academic Search

At Koongarra, Australia, three drill cores from the Cahill Schist Formation containing U-ore, and regolith above it containing secondary U-ore, were studied to ascertain the distribution of rare earth elements (REEs) and U. The unaltered schist has a REE trend similar to the Post Archaean Australian Shale (PAAS), which is, therefore, used as a normalising standard. Unweathered rock from the

Anthony J. Koppi; Robert Edis; Damien J. Field; Harold R. Geering; David A. Klessa; David J. H. Cockayne

1996-01-01

339

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

Microsoft Academic Search

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

E. Tertre; A. Hofmann; G. Berger

2008-01-01

340

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

National Technical Information Service (NTIS)

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

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

1998-01-01

341

Carbonate complexation of yttrium and the rare earth elements in natural waters 1 1 Associate Editor: D. Rimstidt  

Microsoft Academic Search

Potentiometric measurements of Yttrium and Rare Earth Element (YREE) complexation by carbonate and bicarbonate indicate that the quality of carbonate complexation constants previously obtained via solvent exchange analyses are superior to characterizations obtained using solubility and adsorptive exchange analyses. The results of our analyses at 25°C are combined with the results of previous solvent exchange analyses to obtain YREE carbonate

Yu-Ran Luo; Robert H. Byrne

2004-01-01

342

Separation of Actinides from Rare Earth Elements by Electrorefining in LiC1KC1 Eutectic Salt  

Microsoft Academic Search

A pyrometallurgical partitioning technology to recover actinides from high level radioactive wastes is being developed. In the process, actinides are separated from fission products by electrorefining in molten chloride systems. It is expected that REs (rare earth elements), main components of fission products are hardly separated from actinides. In order to estimate separation factors, electrorefining experiments to recover actinides from

Yoshiharu SAKAMURA; Takatoshi HIJIKATA; Kensuke KINOSHITA; Tadashi INOUE; T. S. STORVICK; C. L. KRUEGER; L. F. GRANTHAM; S. P. FUSSELMAN; D. L. GRIMMETT; J. J. ROY

1998-01-01

343

Seasonal dissolved rare earth element dynamics of the Amazon River main stem, its tributaries, and the Curuaí floodplain  

Microsoft Academic Search

We present a comprehensive dissolved rare earth element (REE) data set for the Amazon River and its main tributaries, Rio Negro, Solimões, and Madeira, as well as the Curuaí floodplain. The two-year time series show that REE vary seasonally with discharge in each of the tributaries, and indicate a hydrologically dominated control. Upper crust normalized REE patterns are relatively constant

Gwénaël Barroux; Jeroen E. Sonke; Geraldo Boaventura; Jérôme Viers; Yves Godderis; Marie-Paule Bonnet; Francis Sondag; Sébastien Gardoll; Christelle Lagane; Patrick Seyler

2006-01-01

344

Enrichment and Release of Rare Earth Elements during Weathering of Sedimentary Rocks in Wujiang Catchments, Southwest China  

Microsoft Academic Search

Thirteen weathering profiles of sedimentary rocks such as limestone, dolomitic limestone, dolomite, sillicalite, black shale and purple sandrock from Wujiang catchments were selected for study on enrichment and release behavior of rare earth elements (REE) during weathering, and its impact on plant growth and riverine REE distribution in the catchments with methods of hierachical cluster analysis and mass balance calculation

Zhaoliang Song; Congqiang Liu; Guilin Han; Zhongliang Wang; Zhaozhou Zhu; Cheng Yang

2006-01-01

345

The mobility of the rare earth elements: Evidence and implications from selected terrains affected by burial metamorphism  

Microsoft Academic Search

The mobility of the rare earth element (REE) during hydrous burial metamorphism is described from three localities. Comparison of REE abundances in relict domains and metadomains from flood lavas in the Maddina Volcanics, Fortescue Group, Western Australia shows that, relative to the relict domains, REE may be strongly depleted in certain metadomains. Strong variations in La\\/Yb, La\\/Sm and Eu may

Phillip L. Hellman; Raymond E. Smith; Paul Henderson

1979-01-01

346

Rare earth element geochemistry of hydrothermal deposits from the active TAG Mound, 26°N Mid-Atlantic Ridge  

Microsoft Academic Search

The rare earth element (REE) geochemistry of various phases from the active TAG hydrothermal mound has been examined and related to their mineralogy and fluid chemistry. The mound deposits range from black and white smoker chimneys, massive anhydrite\\/sulphide mixtures, oxides, and ochres. All phases, except black smoker chimney anhydrite, demonstrate a positive Eu anomaly when normalised to chondrite REE values.

Rachel A. Mills; Henry Elderfield

1995-01-01

347

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

Microsoft Academic Search

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

Bruno Reynard; Christophe Lécuyer; Patricia Grandjean

1999-01-01

348

An evaluation of the behavior of the rare earth elements during the weathering of sea-floor basalt  

Microsoft Academic Search

We present rare earth element (REE) data for fresh and altered tholeiitic basalts sampled during a dredging transect at 23°N in the Atlantic Ocean and covering a time span of 0 to 57 million years. These data have been used to evaluate the behavior of the REE during low-temperature weathering processes. Compositional trends from altered basalt interiors to palagonitized rinds

John N. Ludden; Geoffrey Thompson

1979-01-01

349

The behavior of rare earth elements in seawater: Precise determination of variations in the North Pacific water column  

Microsoft Academic Search

The authors present new, highly precise and accurate data for ten rare earth elements (REEs) in two water column profiles and in bottom waters from three additional localities in the North Pacific. Results presented here, and in an earlier publication, indicate that the water column in the western North Pacific is stratified with respect to the isotopic composition of Nd

D. J. Piepgrass; S. B. Jacobsen

1992-01-01

350

Stable isotope and Rare Earth Element evidence for recent ironstone pods within the Archean Barberton greenstone belt, South Africa  

Microsoft Academic Search

There is considerable debate about the mode and age of formation of large (up to ˜200 m long) hematite and goethite ironstone bodies within the 3.2 to 3.5 Ga Barberton greenstone belt. We examined oxygen and hydrogen isotopes and Rare Earth Element (REE) concentrations of goethite and hematite components of the ironstones to determine whether these deposits reflect formation from

Michael T. Hren; Donald R. Lowe; Michael M. Tice; Gary Byerly; C. Page Chamberlain

2006-01-01

351

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

Microsoft Academic Search

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

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

2003-01-01

352

The geochemistry of rare earth elements (REE) in acid mine drainage from the Sitai coal mine, Shanxi Province, North China  

Microsoft Academic Search

In this paper, geochemical characteristics of rare earth elements (REE) in acid mine drainage (AMD) from the Sitai coal mine of Shanxi Province, North China were investigated by determining concentrations of dissolved REEs and major solutes in the AMD samples, concentrations of REEs in the AMD precipitate samples and country rock samples (mudstone and coal), and modeling REEs species in

Fenghua Zhao; Zhiyuan Cong; Hongfu Sun; Deyi Ren

2007-01-01

353

Distribution of U and Th decay series and rare earth elements in sediments of Santos Basin: Correlation with industrial activities  

Microsoft Academic Search

Summary  Santos Basin, located in Southwest Brazil, is considered the most important industrial region of the country. Among the industrial activities present, phosphate fertilizer plants are responsible for the production of 69 million tons of phosphogypsum waste, which is stockpiled in the surrounding environment. This waste concentrates radionuclides of the natural series as well as rare earth elements originally present in

D. I. T. Fávaro; B. P. Mazzilli

2005-01-01

354

Uptake of alkali and alkaline-earth elements on suspended iron and manganese in the kalix river, northern sweden  

Microsoft Academic Search

Scavenging of alkali and alkaline-earth elements by suspended Fe and Mn in the Kalix River, northern Sweden, has been studied for a period of seventeen months. More than 95% (by weight) of suspended nondetrital concentrations of Ca, Mg, and Sr are scavenged on suspended nondetrital Fe throughout all seasons. Barium is correlated to suspended Fe during winter, but during the

Johan Ingri; Anders Widerlund

1994-01-01

355

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

Microsoft Academic Search

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

D. Merten; E. Kothe; G. Büchel

2004-01-01

356

Sums Over States of the Atoms and Singly and Doubly Charged Ions of Rare-Earth Elements  

Microsoft Academic Search

The sums over states of the atoms and singly and doubly charged ions of rare-earth elements that are required for a theoretical study of thermochemical processes in high-temperature plasma spectral sources are calculated in the temperature range 2500–12,000 K.

A. A. Pupyshev; E. V. Semenova

2000-01-01

357

Effect of rare earth elements doping on the electrical properties of (Ba,Sr)TiO3 thin film capacitors  

Microsoft Academic Search

Barium strontium titanate (BST) thin film capacitors are being intensively investigated for tunable microwave devices, because of their high permittivity, low dielectric loss in the microwave region and field dependent permittivity. This study investigates the effect of rare earth elements doping on the electrical properties of BST thin film capacitors. BST thin films were deposited by an RF magnetron sputtering

Nobuo Kamehara; Kazuaki Kwihara

2008-01-01

358

The rare earth elements in rivers, estuaries, and coastal seas and their significance to the composition of ocean waters  

Microsoft Academic Search

The concentrations of the rare earth elements (REEs) in samples from 15 rivers, from 6 estuarine transects, and of 5 coastal seawaters are reported and have been used with literature data to examine the continuity in average REE pattern between average continental crust and the dissolved input of REE to the oceans via estuaries. Concentrations in river waters span a

H. Elderfield; R. Upstill-Goddard; E. R. Sholkovitz

1990-01-01

359

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

PubMed

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

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

2009-05-20

360

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

Microsoft Academic Search

Integrated kraft pulp and paper mill wastewater was characterized before (influent) and after (effluent) the activated sludge process by microfiltration (8, 3, 0.45 and 0.22?m) and ultrafiltration (100, 50, 30 and 3kDa) into different size fractions. Wood extractives, lignin, suspended solids and certain trace elements were determined in each fraction. Forty four percent of the resin and fatty acids in

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

2009-01-01

361

Effect of dietary rare earth elements on growth performance and blood parameters of rats.  

PubMed

Rare earth elements (REE) have been shown to influence growth performance in animal production, especially in pigs. In the present study, the effect of oral administration of rare earth elements on growing rats was investigated. Pure LaCl3 or an REE mixture containing 38% of LaCl3, 52% of CeCl3, 3% of PrCl3 and 7% of chlorides of other REE were used at two different concentrations as supplements to the diets. Fifty male Wistar rats at 4 weeks of age were allotted to five experimental groups: a control group; a La-low group and a La-high group with 75 and 150 mg/kg LaCl3.6H2O, respectively; a REE-low and an REE-high group with 75 and 150 mg/kg REE mixture, respectively. The animals were housed in individual pens. Feed and water were provided ad libitum. After 18 days the oral supplementation of LaCl3.6H2O or of the REE mixture improved daily body weight gain (BWG) by up to 5 or 9% (p > 0.05), respectively. LaCl3.6H2O as well as the REE mixture had positive effects (p < 0.05) on feed conversion ratio (FCR) with a decreased ratio by up to 8 and 11%, respectively. Supplementation of REE also had clear effects on blood serum parameters. The activities of alkaline phosphatase (AP) and alanine amino transferase (ALT) increased significantly (p < 0.05). At the same time, blood glucose level decreased and blood creatine level increased significantly (p < 0.05). There was no significant difference in cholesterol, total protein, albumin and urea nitrogen among the groups. There was no significant difference in triglyceride level between the control and those REE groups, however, a significantly lower (p < 0.01) triglyceride level was found in the 150 mg/kg REE mixture group compared with that in 75 mg/kg REE mixture group and the 150 mg/kg LaCl3.6H2O group. The results suggest that oral supplementation of REE improves growth performance in rats as in pigs. In this respect, concentration and type of REE supplemented to the diets are two important factors herein. PMID:12752829

He, M L; Wang, Y Z; Xu, Z R; Chen, M L; Rambeck, W A

2003-06-01

362

Interferences of oxide, hydroxide and chloride analyte species in the determination of rare earth elements in geological samples by inductively coupled plasma-mass spectrometry  

Microsoft Academic Search

The analytical procedure for the determination of Ba and rare earth elements in rocks and minerals by ICP-MS is described. The yield of mono-oxide and hydroxide ions of Ba and rare earth elements, and chloride ions of Ba has been determined. A Microsoft Excel spreadsheet template has been written to calculate the expected peak intensities for all possible analyte species

Peter Dulski

1994-01-01

363

Rare earth elements in suspended and bottom sediments of the Mandovi estuary, central west coast of India: Influence of mining  

NASA Astrophysics Data System (ADS)

Rare earth elements (REEs) in the suspended particulate matter (SPM) of the Mandovi estuary indicated that the mean total-REEs (?REE) and light REE to heavy REE ratios are lower than that of the average suspended sediment in World Rivers and Post-Archean average Australian shale. High ?REE were associated with high SPM/low salinity and also with high SPM/high salinity. Although the ?REE broadly agree with SPM levels at each station, their seasonal distributions along transect are different. SPM increased seaward in the estuary both during the monsoon and pre-monsoon, but consistently low at all stations during the post-monsoon. The mean ?REE decreased marginally seaward and was <25% at sea-end station than at river-end station. Spatial variations in ?REE are maximum (64%) during the pre-monsoon. Strong to moderate correlation of ?REE with Al, Fe and Mn in all seasons indicates adsorption and co-precipitation of REEs with aluminosilicate phases and Fe, Mn-oxyhydroxides. The ratio of mean ?REE in sediment/SPM is low during the monsoon (1.27), followed by pre-monsoon (1.5) and post-monsoon (1.62). The middle REE- and heavy REE-enriched patterns with positive Ce and Eu anomalies are characteristic at every station and season, both in SPM and sediment. They also exhibit tetrad effect with distinct third and fourth tetrads. Fe-Mn ore dust is the most dominant source for REEs. However, the seasonal changes in the supply of detrital silicates, Fe-Mn ore dust and particulates resuspended from bottom sediments diluted the overall effect of salinity on fractionation and distribution of REEs in the estuary.

Shynu, R.; Rao, V. Purnachandra; Kessarkar, Pratima M.; Rao, T. G.

2011-10-01

364

Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica  

NASA Astrophysics Data System (ADS)

We report the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g-1 for Ce and 0.0035- 0.24 pg g-1 for Lu in glacier ice, and between <0.1-24 pg g-1 for Ce and <0.0004-0.02 pg g-1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC1;characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC1 formation. Interestingly, if the LREE enrichment found in AC1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

Barbante, C.; Gabrielli, P.; Turetta, C.; Planchon, F.; Boutron, C.; Petit, J. R.; Bulat, S.; Hong, S.; Cozzi, G.; Cescon, P.

2009-12-01

365

Geochemical fixation of rare earth elements into secondary minerals in sandstones beneath a natural fission reactor at Bangombé, Gabon  

NASA Astrophysics Data System (ADS)

To study geochemical processes for migration and fixation of fissiogenic rare earth elements (REE) in association with uranium dissolution, in situ isotopic analyses using an ion microprobe were performed on U- and REE-bearing secondary minerals, such as coffinite, françoisite, uraniferous goethite, and uraninite found in a sandstone layer 30 to 110 cm beneath a natural fission reactor at Bangombé, Gabon. Phosphate minerals such as phosphatian coffinite and françoisite with depleted 235U ( 235U/ 238U = 0.00609 to 0.00638) contained large amount of fissiogenic light REE, while micro-sized uraninite grains in a solid bitumen aggregate have normal U isotopic values ( 235U/ 238U = 0.00725) and small amount of fissiogenic REE components. The proportions of fissiogenic and non-fissiogenic REE components in four samples from the core of BAX03 vary in depth ranging from 30 cm to 130 cm beneath the reactor, which suggests mixing between fissiogenic isotopes from the reactor and non-fissiogenic isotopes from original minerals in the sandstone. Significant chemical fractionation was observed between Ce and the other REE in the secondary minerals, which shows evidence of an oxidizing atmosphere during their formation. Pb-isotopic analyses of individual minerals do not directly provide chronological information because of the disturbance of U-Pb decay system due to recent geologic alteration. However, systematic Pb-isotopic results from all of the minerals reveal the mobilization of fissiogenic isotopes, Pb and U from the reactor in association with dolerite dyke intrusion ˜0.798 Ga ago and the formation of the secondary minerals by mixing event between 2.05 Ga-old original minerals and reactor materials due to recent alteration.

Hidaka, Hiroshi; Janeczek, Janusz; Skomurski, Frances N.; Ewing, Rodney C.; Gauthier-Lafaye, François

2005-02-01

366

Dissolved rare earth elements in a seasonally snow-covered, alpine/subalpine watershed, Loch Vale, Colorado  

NASA Astrophysics Data System (ADS)

Dissolved rare earth elements (REEs) were determined in a four-year time series at the outlet of Loch Vale. The Loch Vale watershed is a seasonally snow-covered alpine/subalpine basin in Rocky Mountain National Park, USA. The time series was mainly distinguished by an annual early spring peak in the concentrations of all REEs. REE concentrations at this time were as much as 8-fold greater than at other times of the year. This annual peak was coincident with an early spring peak in dissolved organic carbon (DOC) which results from flushing of soils at the beginning of spring snow melting. The REE/DOC peak occurs as discharge starts to increase from wintertime lows but well before the spring peak in discharge. Speciation considerations suggest complexation of the REEs by DOC. The Ce anomaly also increases (i.e., is less fractionated) during the spring flush indicating that the most reducing (or least oxidizing) REE sources in the system are comparatively more important at that time. Mn data and the La/Yb ratio also support this. The behavior of REEs in the Loch Vale system has additionally been compared with metal and DOC behavior in other systems. Hydrologic and climatic differences can be important especially with regard to timing and duration of the spring flush peak. Damping of hydrologic events in the lower floodplain of major rivers may also partially result in the differences observed between Loch Vale and the lower Mississippi River. However, comparison with the Amazon River system additionally suggests that seasonal flooding of wetlands may be an important regulator of REE concentrations. Chemical differences are also important for these systems. This includes pH and suspended matter concentrations which affect the balance between adsorption and complexation. Additionally, the relative complexing ability of DOC in different systems is a factor needing further consideration.

Shiller, Alan M.

2010-04-01

367

Forms of rare earth elements' sorption by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris  

NASA Astrophysics Data System (ADS)

The adsorption of a mixture of 16 isotopes of 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) present in the initial solution in equal concentrations by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris was studied under different acidity conditions. The solution pH was apparently the leading factor in the interaction of rare earth ions with the surface of mineral and biological sorbents. These interactions were controlled by electrostatic forces in acid (pH 4) and neutral (pH 7) solutions; the precipitation of elements from the solution was the predominant mechanism under alkaline conditions (pH 9). Microorganisms affected the adsorption of lanthanides by quartz in the entire pH range under study, especially at pH 7. In the presence of bacteria, the adsorption of the elements studied by goethite increased in an acid solution, remained unchanged under neutral conditions, and slightly decreased under alkaline conditions. Microorganisms increased the concentration of nonexchangeable forms of the elements adsorbed on the surface of quartz and goethite, which could be due to the formation of low-soluble complexes of rare earth elements with organic substances produced by bacteria.

Perelomov, L. V.; Perelomova, I. V.; Yoshida, S.

2009-12-01

368

Electron affinities of alkaline-earth and actinide elements calculated with the local-spin-density-functional theory  

SciTech Connect

The generalized exchange local-spin-density-functional theory withself-interaction correction and correction of the statistical exchangepotential was used to calculate the electron affinities of alkaline-earth andactinide elements. The effect of relativistic correction by the mass velocityand Darwin terms and correlation correction on the electron affinities isdiscussed. The calculation of the negative ions shows that, although thecorrelation correction to the potential is very small, it is essential forobtaining converged values for most of the negative ions. The calculatedresults predict stable negative ions for the alkaline-earth elements Ca, Sr,Ba, and Ra, supporting the calculations of Vosko /ital et/ /ital al/. (Phys. Rev. A39, 446 (1989)) and Fischer (Phys. Rev. Lett. 59,2263 (1987); Phys. Rev. A 39, 963 (1989)). Estimated electronaffinities for the actinide elements are given.

Guo, Y.; Whitehead, M. A.

1989-07-01

369

Rare earth element geochemistry of the Betts Cove ophiolite, Newfoundland: complexities in ophiolite formation  

NASA Astrophysics Data System (ADS)

The Betts Cove ophiolite includes the components of typical ocean crust: pillow lavas, sheeted dikes, gabbros and ultramafics. However, the trace element geochemistry of basaltic rocks is unusual. Three geochemical units are recognized within the lava and dike members. Within the pillow lavas, the geochemical units correspond to stratigraphic units. Upper lavas have `normal' ( i.e ., typical for ocean floor basalts) TiO 2 contents (0.75 to 2.0 wt%), heavy rare earth elements (HREE) values in the range 6-20× chondrites and chondrite-normalized REE patterns with relative LREE depletion. Intermediate lavas have TiO 2 contents between 0.30 and 0.50 wt%, HREE contents from 4-7× chondrites and extreme relative LREE depletion. Lower lavas have anomalously low TiO 2 contents (<0.30 wt%) and unusual convex-downwards REE patterns with REE abundances around 2-5 × chondrite. These geochemical differences can be explained if the three groups were derived from different mantle sources. Independent mantle sources for the three units are consistent with their different 143 Nd / 144 Nd ratios varying at 480 m.y.B.P. from 0.51222 in a lower lava to 0.51238 in an upper lava. The upper lavas may be partial melts of a source similar in composition to that of modern MORB, the intermediate lavas may be from a very depleted oceanic mantle (second stage melt), and the lower lavas may have formed by melting an extremely depleted mantle that had been invaded by a LREE-enriched fluid. A possible tectonic environment where these different sources could be juxtaposed is a back-arc or inter-arc basin.

Coish, R. A.; Hickey, R.; Frey, F. A.

1982-11-01

370

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

371

Microwave absorbing properties of rare-earth elements substituted W-type barium ferrite  

NASA Astrophysics Data System (ADS)

W-type barium ferrites Ba(MnZn)0.3Co1.4R0.01Fe15.99O27 with R=Dy, Nd and Pr were prepared by chemical coprecipitation method. Effects of rare-earth elements (RE) substitution on microstructural and electromagnetic properties were analyzed. The results show that a small amount of RE3+ ions can replace Fe3+ ions and adjust hyperfine parameters. An obvious increase in natural resonance frequency and high frequency relaxation, and a sharp decrease for complex permittivity have been observed. Furthermore, the matching thickness and the reflection loss (RL) of one-layer ferrite absorber were calculated. It reveals that thin and broad-band can be obtained by RE-substitution. But only when the magnetic moment of RE3+ is higher than that of Fe3+, can substitution be effective for higher RL. Dy-substituted ferrite composite has excellent microwave absorption properties. The frequency (with respect to -10 dB RL) begins from 9.9 GHz, and the bandwidth reaches far more than 8.16 GHz. The peak value is -51.92 dB at a matching thickness of 2.1 mm.

Jing, Wang; Hong, Zhang; Shuxin, Bai; Ke, Chen; Changrui, Zhang

2007-05-01

372

Effect of paleosol formation on rare earth element signatures in fossil bone  

NASA Astrophysics Data System (ADS)

The rare earth element (REE) content of fossil bones was analyzed and compared with the degree of ancient pedogenic development and depositional environments from several locations in the Orellan Scenic Member of the Oligocene Brule Formation in Badlands National Park, South Dakota. Paleosols ranged from weakly developed Entisols to more strongly developed Inceptisols, all typical of fluvial environments and possible paleocatena variation. Paleosols were alkaline and well drained. Sediments with sparse soil features from an oxbow lake system suggest that conditions were too waterlogged and sedimentation rates too rapid for significant pedogenesis. The variance of REE signatures in fossil bones from the paleosol sites was significantly greater than that of fossils from minimally altered sediments of the former oxbow lake. Positive Ce anomalies were associated with low U concentrations and indicate paleoredox conditions. Greater degrees of pedogenesis, regardless of the horizon in which the bone was found, systematically correlated with increased heavy REE enrichment in fossil bones. The fossil-bone REE signatures from the different paleosols and depositional environments were significantly different and distinguishable.

Metzger, Christine A.; Terry, Dennis O., Jr.; Grandstaff, David E.

2004-06-01

373

Geochemistry of rare earth elements of playa sediments from the eastern Thar desert, India.  

NASA Astrophysics Data System (ADS)

The saline lakes (Sambhar, Didwana, Kuchaman and Phulera) occurring in the eastern part of the Thar desert (Rajasthan, India), in front of the Aravalli mountain range provide a prominent example for alkaline brine and evaporites. The chemical evolution of lakes has resulted in the precipitation of (mainly) halite together with minor amounts of anhydrite, thenardite, mirabilite, kieserite, sylvite and trona, occurring in the evaporitic crusts of all these lakes (except Phulera). Phulera exhibits a carbonaceous crust, consisting of calcite and Ca-Mg-carbonates (dolomite and huntite). Quartz and several silicates in these playas are of detrital origin, brought into the playas by aeolian and subordinately fluvial transport processes. The contents of rare earth elements (REE) were determined quantitatively in some selected sediment samples from the above mentioned playa lakes. The REE patterns seems to be comparable for all the studied samples and with that of upper continental crust and PAAS of Taylor and McLennen (1985). But the amount of REE differs from sample to sample, showing the highest values in sediments being rich in detrital minerals than that of evaporite rich. Among the evaporites the higher abundance of REE occurs in the carbonates than chlorides and sulphates.

Roy, P. D.; Smykatz-Kloss, W.

2003-04-01

374

Rare-earth elements in geothermal waters from Oregon, Nevada, and California  

NASA Astrophysics Data System (ADS)

The concentrations of rare-earth elements (REE) were determined in thermal waters from hot springs in the Oregon Cascades and southeastern Oregon, and from wells in the Beowawe (NV), Dixie Valley (NV) and Heber (CA) geothermal fields. The waters are all near-neutral to slightly alkaline, and dominated by sodium chloride or sodium bicarbonate. Concentrations of REE range from <10-6 to approximately 10-3 times chondrite. In general, filtered aliquots of the fluids contain substantially less REE (sometimes by an order of magnitude or more) than corresponding unfiltered aliquots, suggesting a considerable particulate contribution to the total REE. Concentrations of REE in the waters from Beowawe and Dixie Valley are generally quite low, possibly owing to loss of REE on boiling. Most of the waters exhibit LREE-enriched, chondrite-normalized REE patterns, with slight or non-existent Eu anomalies. The main exceptions are the waters from Heber, which exhibit a concave-upward pattern with a prominent, positive Eu anomaly (``Mexican hat'' pattern). The behavior of REE in waters from continental geothermal systems is a useful indicator of water-rock interaction and holds promise as a potential tool for exploration.

Wood, Scott A.; Shannon, William M.

2003-02-01

375

Rare earth element geochemistry of spring water, north western Bam, NE Iran  

NASA Astrophysics Data System (ADS)

In this paper, based on the analysis of major ions and rare earth elements (REEs), spring water samples from the north western Bam area, central Iran were investigated for the hydrochemical processes, geochemical behavior of REEs and ion concentration background in the region . In the study area, the order of cation and anion abundance is Na+ > K+ > Mg2+ > Ca2+ and Cl- > SO{4/-2} > HCO3 - > NO3 -, and the dominated hydrochemical water are of Na-Cl type. The groundwater shows heavy REEs enrichment relative to light REEs. Depending on water types, REEs show different behaviors in study area. The increase in TDS and Fe contents in groundwater is accompanied by an increase in REE concentrations, while an increase in pH and Eh values is accompanied by a decrease in REE concentrations. Moreover, correlation analysis indicates that Eh-pH condition, TDS and Fe content, aquifer rock as well as their minerals play an important role in controlling the REE enrichment of groundwater.

Pazand, Kaveh; Javanshir, Ali Reza

2013-09-01

376

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

377

Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa  

Microsoft Academic Search

Shale-normalized rare-earths and yttrium (REYSN; Y inserted between Dy and Ho) patterns for detritus-free samples from both the Kuruman and Penge Iron-Formations (IFs) in the Late-Archaean to Early-Palaeoproterozoic Transvaal Supergroup display pronounced heavy rare-earth element (REE) enrichment, and positive anomalies of LaSN, EuSN, GdSN, YSN, and ErSN, but neither positive nor negative CeSN anomalies. Excepting CeSN and EuSN anomalies, the

Michael Bau; Peter Dulski

1996-01-01

378

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

379

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

SciTech Connect

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., 3 figs., 3 tabs.

Close, D.A.; Parker, J.L.; Haycock, D.L. (Los Alamos National Lab., NM (United States)); Dragnev, T. (International Atomic Energy Agency, Vienna (Austria))

1991-01-01

380

Rare Earth Element Behavior During Incongruent Weathering and Varying Discharge Conditions in Silicate Dominated River Systems: The Australian Victorian Alps  

NASA Astrophysics Data System (ADS)

The distribution of rare earth elements (REE) and trace elements was measured by ICP-MS on fresh, slightly weathered and weathered granite and surface water samples from a network of 11 pristine rivers draining the Australian Victorian Alps during (i) high and (ii) low discharge conditions. River water REE concentrations are largely derived from atmospheric precipitation (rain, snow), as indicated by similar Chondrite normalized REE patterns (higher LREE over HREE; negative Ce anomalies, positive Eu anomalies) and similar total REE concentrations during both dry and wet seasons. Calculations based on the covariance between REE and Cl concentrations and oxygen and hydrogen isotopes indicate precipitation input coupled with subsequent evaporation may account for 30% o 100% of dissolved REE in stream waters. The dissolved contribution to the granitic substratum to stream water comes mainly from the transformation of plagioclase to smectite, kaolinite and gibbsite and minor apatite dissolution. However, since most REE of the regional granite are present in accessory minerals (titanite, zircon, etc.) they do not significantly contribute to the river REE pool. REE concentrations drop sharply downstream as a result of dilution and chemical attenuation. A trend of downstream enrichment of the heavier REE is due to selective partitioning of the lighter REE (as both free REE or REECO3 complexes) to hydrous oxides of suspended Al which, in turn, is controlled by a downstream increase of pH to values > 6.1 (for free REE) and > 7.3 (for REECO3 complexes). Although most circumneutral waters were supersaturated with REE phosphate compounds, precipitation of LnPO4 is not believed to have been a dominant process because the predicted phosphate fractionation pattern is inconsistent with the observed trends. Negative saturation indices of hydrous ferric oxides also militate against surface complexation onto goethite. Instead, REE attenuation most likely resulted from adsorption onto hydrous aluminium oxide. Seasonally, higher total REE concentrations during the dry season are due to longer residence time of water within rock fractures as well as high rainfall REE concentrations which, for the summer of 2007, might be related to organic carbon rich dust released after bushfires in the region. Lower pH values and low oxidation potentials at that time also contribute to raise REE concentrations through desorption.

Hagedorn, K. B.; Cartwright, I.

2008-12-01

381

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

NASA Astrophysics Data System (ADS)

The behaviour of rare earth elements (REE) during fluid-rock interaction in mid-crustal shear zones has received little attention, despite their potential for mass balance calculation and isotopic tracing during deformation. In this study, several cases of large REE mobility during Alpine fluid-driven shear zone development in the pre-Alpine granitic basement of the Mont Blanc Massif are considered. On a regional scale, the undeformed granite compositions range within 5 wt% SiO 2 (70.5-75.3 wt%) and magmatic chemical variations are of the order of 10-20%, ascribed to minor effects of crystal fractionation. Major and trace element mobility observed in shear zones largely exceeds these initial variations. Shear zones developed a range of mineral assemblages as a result of shearing at mid-crustal depths (at ˜0.5 GPa, 400°C). Five main shear zone assemblages involve muscovite, chlorite, epidote, actinolite and calcite, respectively, as major phases. In most cases, selective enrichments of light or heavy REE (and Y, Ta, Hf) are observed. REE mobility is unrelated to deformation style (cataclastic, mylonitic), the intensity of strain, and to the shear zone's major metamorphic mineral assemblages. Instead, the changes in REE concentrations are ascribed to the alteration of pre-existing magmatic REE-bearing minerals during deformation-related fluid-rock interaction and to the syntectonic precipitation of metamorphic REE-bearing minerals (mainly monazite, bastnäsite, aeschynite and tombarthite). Minor proportions (<2%) of these accessory phases, with grain sizes mostly <20 ?m, account for enrichments of up to 5:1 compared to the initial granite whole-rock REE budget. The stability of the REE phases appears to be largely dependent on the altering fluid composition. REE mobility is ascribed to changes in pH and to the availability of CO 32-, PO 42-, and SO 42-ligands in the fluid. Such processes are likely to influence the mobility of REE, Y, Hf and Ta in shear zones.

Rolland, Yann; Cox, Stephen; Boullier, Anne-Marie; Pennacchioni, Giorgio; Mancktelow, Neil

2003-09-01

382

The Koshak section: Evidence for element fractionation and an oxidation event at the K/T boundary  

NASA Astrophysics Data System (ADS)

The Koshak site is a new K/T section located about 125 km EEN of the Fort Shevchenko city, Mangyshlak, Kazakhstan. In this paper, we report results of geochemical and mineralogical studies of this section which indicate a deep element fractionation and an oxidation event at the K/T boundary.

Nazarov, M. A.; Badjukov, D. D.; Barsukova, L. D.; Kolesov, G. M.; Naidin, D. P.

1993-03-01

383

Analytical modelling and finite element computation of radial vibration force in fractional-slot permanent magnet brushless machines  

Microsoft Academic Search

Analytical models have been developed for analysing the radial vibration force in fractional-slot permanent magnet machines and validated extensively by finite element analyses. They are used to investigate the influence of (a) stator slotting, (b) tangential field component, (c) radius in the airgap for computation, and (d) load condition etc. on the radial vibration force calculation. The major findings can

Z. Q. Zhu; Z. P. Xia; L. J. Wu; G. W. Jewell

2009-01-01

384

Spectral finite element approach to postseismic deformation in a viscoelastic self-gravitating spherical Earth  

NASA Astrophysics Data System (ADS)

Theoretical models of the viscoelastic relaxation of a spherical Earth are derived to model large-scale postseismic deformation resulting from great earthquakes (M > 7) over decadal timescales. Most existing models of postseismic deformation do not consider strong lateral heterogeneities in mantle viscosity, in particular in the subducting slab where such events occur. In addition, the self-gravitation effect is often treated only approximately. Both effects become important when observations from space geodetic techniques such as GPS and GRACE are interpreted. In this paper, we present a spectral finite-element approach that allows these two effects to be considered in a rigorous way. In this way, much larger lateral viscosity variations can be handled than by perturbation techniques. We derive interface conditions for an arbitrary shear fault in the form of double-couple forces that are equivalent to a prescribed dislocation and simulate a relaxation process for an incompressible Maxwell earth with a 3-D viscoelastic structure. Computational results are validated for a spherically symmetric model by an independent method based on the inverse Laplace integration, and good agreement is obtained. As an example, we apply this approach to the 2004 Sumatra-Andaman earthquake and simulate a large-scale postseismic gravity potential variation by a forward calculation. In the presence of a slab, the secular variation in geoid height change decreases by 30 per cent for wavelengths longer than 500km, with respect to the case excluding the slab. The effect of the slab can exceed 0.3mmyr-1 for short-term variations when the asthenosphere viscosity is 1019Pas, which are larger than the observation errors of GRACE. For a displacement field, a decrease in deformation rates can amount to 70 per cent due to the inclusion of a slab, which is detectable with geodetic observations such as GPS. The effect of the slab is attenuated in the gravity field for such longer wavelengths since horizontal scales of the slab are smaller than its spatial resolution. Lateral heterogeneities in viscosity due to a slab should therefore be considered for interpreting observed postseismic relaxation due to a large thrust event in a subduction zone.

Tanaka, Y.; Klemann, V.; Fleming, K.; Martinec, Z.

2009-03-01

385

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

386

Constraining Major Element Fractionation in an Alkali Gabbroic Sill using Mass Balance Modelling.  

NASA Astrophysics Data System (ADS)

The Ringkallen hill gabbro (RHG) is an ~225m thick layered alkali gabbroic sill in central Sweden. It is a part of the much larger ~1.26 Ga Ulvö Gabbro complex, a series of 200-300m thick saucer-shaped alkali gabbroic intrusions with diameters of 30-80km. The anorthite (An.) content of plagioclase decrease gradually from ~70% at the margins to ~45% at the Sandwich Horizon, and the bulk composition of the RHG calculated from whole-rock analyses closely resembles the chilled margin composition, suggesting that the intrusion crystallised from a single pulse of magma in a closed system. Mass balance calculations were used to calculate the evolution of the supernatant liquid to the point where 90% of the intrusion had crystallised. The results show a successive decrease in the concentration of Al2O3 and MgO, an increase in MnO, TiO2, Na2O and K2O, while the concentrations of SiO2 and CaO remain stable. The major element variations of the calculated supernatant liquid were used to constrain the proportion between cumulus phases and crystallising liquid fraction (CLF). By iteratively changing the bulk partition coefficient by varying the proportion between the cumulus phases and the CLF for a given interval, the best estimate was found using root mean square method. The results indicate that the intrusion crystallised with a CLF of ~0.8 for the first 50% of crystallisation, and the next 30% had an estimated CLF of ~0.6 and the final 10% had ~0.8 CLF. At the point where 90% of the intrusion had crystallised, the stratigraphy contained only ~25% cumulus minerals. In strong contrast, simulation of the stratigraphic decrease in An. content of plagioclase by thermodynamic modelling suggests more than 70% fractional crystallisation. The strong stratigraphic decrease of plagioclase An. content is inconsistent with the modest change of the An. content of the calculated liquid. This suggests that the linear partitioning in the binary plagioclase system for these alkali gabbroic intrusions may be different from experimental results.

Ek, M.; Hogmalm, K. J.; Larson, S.-Å.

2012-04-01

387

Preconcentration and determination of rare-earth elements in iron-rich water samples by extraction chromatography and plasma source mass spectrometry (ICP-MS)  

Microsoft Academic Search

A 100-fold preconcentration procedure based on rare-earth elements (REEs) separation from water samples with an extraction chromatographic column has been developed. The separation of REEs from matrix elements (mainly Fe, alkaline and alkaline-earth elements) in water samples was performed loading the samples, previously acidified to pH 2.0 with HNO3, in a 2ml column preconditioned with 20ml 0.01M HNO3. Subsequently, REEs

Carolina Hernández González; Alberto J. Quejido Cabezas; Marta Fernández Díaz

2005-01-01

388

Experimental determination of partition coefficients for rare earth and high-field-strength elements between clinopyroxene, garnet, and basaltic melt at high pressures  

Microsoft Academic Search

Clinopyroxene\\/melt and garnet\\/melt partition coefficients have been determined for Ti, Sr, Y, Zr, Nb, Hf, and rare earth\\u000a elements from 19 doped experiments on 1921 Kilauea basalt. The experiments were carried out from 2.0 to 3.0 GPa and 1310°\\u000a to 1470?°C. The purpose was to derive a set of partition coefficients for high-field-strength elements (HFSE) and rare earth\\u000a elements (REE)

Kevin T. M. Johnson

1998-01-01

389

Submarine groundwater discharge of rare earth elements: Evidence of an important trace element flux to coastal waters  

NASA Astrophysics Data System (ADS)

Johannesson and Burdige [2007, EPSL 253, 129] suggested that submarine groundwater discharge (SGD) represents a substantial, unrecognized source of Nd to the oceans. Based on a globally averaged terrestrial SGD flux equal to 6 percent of the global river discharge and mean groundwater Nd concentrations obtained from the literature, we estimated a global SGD Nd flux that was within a factor of 2 of the previously proposed missing global Nd flux. To test our hypothesis that SGD is an important source of Nd to the oceans, rare earth element (REE) concentrations were measured in SGD samples collected beneath a coastal lagoon on the Florida Atlantic coast (Indian River Lagoon). Shale (PAAS)-normalized REE patterns for all SGD samples exhibit substantial enrichments in the heavy REEs (HREE) compared to the light REEs (LREE) as shown by their PAAS-normalized Yb/Nd ratios, which range from 5 to 73 (mean = 16). SGD from piezometers located 10 m and 22.5 m from shore exhibit PAAS-normalized REE plots that are most similar to the patterns of the overlying lagoon (surface) water. For example, mean PAAS-normalized Yb/Nd ratios for groundwaters sampled from the 10 m and 22.5 m piezometers are 6.7 and 8.3, which compare well with the PAAS- normalized Yb/Nd ratio of water column samples (8.7). In contrast, the mean PAAS-normalized Yb/Nd ratio of terrestrial-derived groundwater from the piezometer at the shoreline is 41. Neodymium concentrations of the SGD samples range from 230 to 2400 pmol/kg (mean = 507 pmol/kg), and thus are substantially higher than reported for open ocean seawater (typical Nd = 20 pmol/kg). Based on SGD fluxes previously determined with seepage meters, porewater Cl concentrations, and Rn-222 deficiencies of porewaters [Martin et al., 2007, Water Resour. Res. 43, W0544, doi: 10.1029/2006WR005266], we estimate daily inputs of Nd to the Indian River Lagoon of 50 to 2100 umoles for the terrestrial-derived component of SGD, and 171 mmoles for the marine component of SGD (81 to 3400 times greater). Residence times of Nd in the portion of the lagoon studied are estimated to range from 6 to more than 250 years based on the terrestrial-derived SGD flux of Nd, compared to 26 days using the marine-derived SGD flux of Nd. The substantially shorter residence time determined using the marine-derived SGD component compares well with the estimated flushing time for this portion of the estuary (~3 weeks). The similarity between SGD and lagoon water Nd concentrations and PAAS-normalized REE patterns, in conjunction with the larger, marine-derived SGD flux of Nd, strongly suggests that recirculation of lagoon water and subsequent SGD exerts the principal control on Nd concentrations in the lagoon. The elevated Nd concentration for deep groundwater (186 cmbsf) located 22.5 m from shore also agrees well with another study that reported recirculated, marine SGD as a source of REEs to coastal waters [Duncan and Shaw, 2003, Aquatic Geochem. 9, 233]. Thus, our observations demonstrate the importance of recirculated, marine SGD to these lagoon surface waters, and further support our hypothesis that SGD contributes substantial fluxes of Nd to the coastal oceans.

Johannesson, K. H.; Chevis, D.; Burdige, D. J.; Cable, J. E.; Martin, J. B.; Roy, M.

2008-12-01

390

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

391

Effect of low doses of dietary rare earth elements on growth performance of broilers.  

PubMed

The present study was designed to investigate effect of dietary rare earth elements (REE), including both organic and inorganic compounds, on growth performance of broilers. In experiment 1, a total of 180 male Ross broiler chicks were allocated to 72 pens with different assignment: four chicks per pen or individually. The following three treatment diets were applied: control, REE-chlorides at a dose of 40 mg/kg and REE-citrate at a dose of 70 mg/kg. Each treatment group had 24 pens containing both assignments (12 pens each). In experiment 2, a total of 72 male 3-day-old Ross broiler chicks were separated to four groups: control, REE-chlorides at a dose of 70 mg/kg and REE-citrate at doses of 70 mg/kg and 100 mg/kg. In experiment 1, dietary REE-citrate improved body weight gain during the overall period by 5.0% (p < 0.05) while the increase with REE-chloride was not significant. In experiment 2, growth effects (p < 0.05) were only found in the period from day 21 to slaughter with all REE forms, and feed conversion ratio was improved by 3.4% (p < 0.05) with REE-citrate. No significant effects of REE were found on chill weight, percentages of breast meat, thigh weight, drumstick weight and wing weight. Concentrations of La and Ce in the liver and muscles were very low, accounting for 0.11-0.76 and 0.02-0.30 mg/kg respectively. There was weak tendency for a dose-response relationship especially in the groups supplemented with REE-chlorides. The main blood serum biochemical parameters were not significantly affected by REE in the diets. The results suggest that dietary supplementation of low doses of REE-citrates might improve growth performance of broilers without affecting carcass composition and health of the broilers. PMID:19364383

He, M L; Wehr, U; Rambeck, W A

2009-03-31

392

Recovery and separation of rare earth elements using columns loaded with DNA-filter hybrid.  

PubMed

Given that the supply of several rare earth elements (REEs) is sometimes limited, recycling REEs used in various advanced materials, such as Nd magnets, is important for realizing efficient use of REE resources. In the present work, the feasibility of using DNA for REE recovery and separation was examined, along with the identification of the binding site of REEs in DNA. In particular, a DNA-cellulose filter paper hybrid was prepared so that DNA-based materials can be used for the separation of REEs using columns loaded with DNA. N,N'-Disuccinimidyl was used as a cross-linker reagent for the fixation of DNA onto a fibrous cellulose filter. The results showed that (i) the DNA-filter hybrid has a sufficiently high affinity to adsorb REEs; (ii) the adsorption capacity was 0.182 mg/g for Nd; and (iii) the affinity of REEs for DNA was stronger for REEs with larger atomic numbers. The difference of the affinity among REEs in the third result was compared with the adsorption patterns of REEs discussed in the literature. The comparison suggests that phosphate in the DNA-filter paper hybrid was responsible for REE adsorption onto the hybrid. The results were supported by the Nd, Dy, and Lu L(III)-edge EXAFS; the REE-P shell was identified for the second neighboring atom, showing the importance of the phosphate site as REE binding sites. The difference in the affinity among REEs suggest that group separation of REEs (such as La, Ce, (Pr and Nd), (Ho, Dy, and Er), (Tb and Gd), (Sm, Eu), Tm, Yb, and Lu) is possible, although complete isolation of each REE from a solution containing all REEs may be difficult. For practical applications, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste using columns loaded with the DNA-filter hybrid. PMID:23059995

Takahashi, Yoshio; Kondo, Kazuhiro; Miyaji, Asami; Umeo, Miyuki; Honma, Tetsuo; Asaoka, Satoshi

2012-01-01

393

Nernst-Ettingshausen Effect in Elemental Rare-Earth Single Crystals  

NASA Astrophysics Data System (ADS)

The transverse Nernst-Ettingshausen (N-E) coefficient N measurements of the elemental rare-earth (R-E) single-crystal are for the first time presented from 80 to 420 K. Since they have mainly hexagonal symmetry at room temperature, measurements are given with the heat flux along the [100] and the [001] axes. Due to their complex band structure and Fermi surface, their small thermopower (S) and their multicarrier systems involving electron (e) and hole (h) pockets, their N are expected to be large. Indeed, for such systems, both S and N can be expressed as^1 S=(Se?e+ Sh?h)/( ?e+?h) while N=[(Ne?e+ Nh?h)( ?e+?h)+(Sh-Se)(RHh?h- RHe?e)?e?h]/( ?e+?h)^a, where ? is the electrical conductivity and RH the Hall coefficient and the subscript correspond to either carriers. Since Sh>0 and Se<0, the resulting S should be low thus leading to a large N . These solids are useful in single-material thermoelectric N-E coolers. They create a large temperature differences using thermomagnetic effects, without having to be cascaded. This would resolve th problem of contact resistances of actual multi-stage Peltier coolers, especially in the cryogenic temperature range. The dimensionless figure of merit of N-E coolers is zTN=B^2N^2?(B)T/?(B), with B is the magnetic field, T the absolute temperature and ? the thermal conductivity. a.E.H. Putley, The Hall Effect and Semiconductor Physics , New York: Dover publication, 1968.

Chamoire, Audrey; Heremans, Joseph

2012-02-01

394

Geochemical characteristics of rare earth elements in soil of the Ditru Massif, Eastern Carpathians, Romania  

NASA Astrophysics Data System (ADS)

The present paper describes the level of rare earth elements in soils developed from Ditr?u massif area for evaluating of the background of these elements and accurate assessment of environmental impact. Also this paper contributed to understanding the important role of parent rocks in pedogenic processes. The Ditr?u Alkaline Massif represent an intrusion body with a internal zonal structure, which was emplaced into pre-Alpine metamorphic rocks of the Bucovinian nappe complex close the Neogene - Quaternary volcanic arc of the Calimani-Guurghiu- Harghita Mountain chain. The center of massif was formed by nepheline syenite, which is surrounded by syenite and monazonite. North-western and north-eastern marginal sectors are composed of hornblende gabbro/hornblendite, alkali diorite, monzodiorite, monzosyenites and alkali granite. Small discrete ultramafic bodies (kaersutite-bearing peridotite, olivine, pyroxenite and hornblendite) and alkali gabbros occur in the Jolotca area. All this rocks are cut by late-stage dykes with a large variety of composition including tinguaite, phonolite, nepheline syenite, microsyenite, and aplite. The types of soils predominant in this zone are lithosoils. These soils are shallow developed, have low content in organic matter and reflects mineralogical and geochemical composition of the bedrock. The soil samples were collected from 70 location for all type of representative rocks (approximately 10 soil sampling points for each type of rock). The samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The pH values of these samples varied from 3.6 to 7.3, in general, the soils from massif area are acid or weakly acidic. The pH controls the abundance of REE in soil, the concentration of REE increases with decreasing pH values. In soil samples analyzed the contents of REE follow the order: Ce > La > Nd > Pr > Sm > Eu > Gd > Dy > Yb > Er > Tb > Ho >Tm. ? REE varied from 52.59 ?g g-1 to 579.2 ?g g-1 , the average is 273.14 ?g g-1. The chemical analysis of soil showed an enrichment in LREE (from La to Eu) and a depletion in HREE (from Gd to Lu). Relatively high levels of LREE concentration in soil are genetically associated with REE mineralization. The soil samples developed on the syenite and nephelin syenite are enriched in HREE. The REE chondrite - normalized plots showed for most soils in the sampling area strongly negative anomalies for cerium and europium, positive anomalies for gadolinium and dysprosium. The distribution of REE in soil is given and controlled by the presence of primary minerals (potasic and plagioclase feldspars) and accessory minerals (zircon, monazite, titanite, allanite, apatite, xenotime, thorite, bastnäsite) in bedrock.

Ion, Adriana

2013-04-01

395

Carbonate complexation of yttrium and the rare earth elements in natural waters  

NASA Astrophysics Data System (ADS)

Potentiometric measurements of Yttrium and Rare Earth Element (YREE) complexation by carbonate and bicarbonate indicate that the quality of carbonate complexation constants previously obtained via solvent exchange analyses are superior to characterizations obtained using solubility and adsorptive exchange analyses. The results of our analyses at 25°C are combined with the results of previous solvent exchange analyses to obtain YREE carbonate complexation constants over a wide range of ionic strength (0 ? I ?3 molal). YREE carbonate complexation constants are reported for the following equilibria, M 3++nHCO 3-?M(CO 3) n3-2n+nH +, where n = 1 or 2. Formation constants written in terms of HCO 3- concentrations require only minor corrections for ion pairing relative to the corrections required for constants expressed in terms of CO 32- concentrations. Formation constants for the above complexation equilibria, CO3H? 1=[MCO 3+][H +][M 3+] -1[HCO 3-] -1 and CO3H? 2=[M(CO 3) 2-][H +] 2[M 3+] -1[HCO 3-] -2, have very similar dependencies on ionic strength because the reaction MCO 3++HCO 3-?M(CO 3) 2-+H + is isocoulombic. Potentiometric analyses indicate that the dependence of log CO3H? 1 and log CO3H? 2 on ionic strength at 25°C is given as logCO3H? n= logCO3H? n0-4.088 I0.5/(1+3.033 I0.5)+0.042 I where CO3H? n0 denotes a formation constant at 25°C and zero ionic strength. Recommended values for log CO3H? 1 and log CO3H? 20, expressed in the form (element, -log CO3H? 10, -log CO3H? 20), are as follows: (Y, 2.85, 8.03), (La, 3.60, 9.36), (Ce, 3.27, 8.90), (Pr, 3.10, 8.58), (Nd, 3.05, 8.49), (Sm, 2.87, 8.13), (Eu, 2.85, 8.03), (Gd, 2.94, 8.18), (Tb, 2.87, 7.88), (Dy, 2.77, 7.75), (Ho, 2.78, 7.66), (Er, 2.72, 7.54), (Tm, 2.65, 7.39), (Yb, 2.53, 7.36), (Lu, 2.58, 7.29).

Luo, Yu-Ran; Byrne, Robert H.

2004-02-01

396

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

397

Analysis of the electronic dipole polarizability of ions in cubic oxides, fluorides, and sulfides of alkaline earth elements  

NASA Astrophysics Data System (ADS)

A new approach to calculating the electronic dipole polarizability of ions in crystals which is based on an analysis of the relationship between the electronic dipole polarizability of ion and its effective charge has been proposed. It is shown that applying this method to simple cubic oxides, fluorides, and sulfides of alkaline earth elements yields makes the calculation results consistent with the well-known data on the structure and type of bonds in these compounds.

Yatsenko, A. V.

2010-07-01

398

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

Microsoft Academic Search

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., pKMHA for type A sites, consisting mainly of carboxylic acids), required by the

Jianwu Tang; Karen H. Johannesson

2003-01-01

399

Rare Earth Element Contents of High pCO 2 Groundwaters of Primorye, Russia: Mineral Stability and Complexation Controls  

Microsoft Academic Search

The rare earth element (REE) geochemistry of cold, high pCO2 groundwaters was studied in springs and boreholes in the Primorye region of the Russian Far East. The gas phase in these\\u000a waters is dominated by mantle-derived CO2 (up to 2.6 atm.), being introduced to shallow groundwaters along major fault systems. The aggressive nature of these moderately\\u000a acidic groundwaters has led

Paul Shand; Karen H. Johannesson; Oleg Chudaev; Valentina Chudaeva; W. Mike Edmunds

400

A rare earth element study of complex zircons from early Archaean Am??tsoq gneisses, Godthåbsfjord, south-west Greenland  

Microsoft Academic Search

We present high spatial resolution ion-microprobe rare earth element (REE) data for discrete growth phases of complex polyphase zircons from early Archaean Am??tsoq gneisses, outer Godthåbsfjord, SW Greenland. In Matsuda diagrams, the two major growth phases, >3.8Ga cores and ca. 3.65Ga rims, have steep positive slopes from La to Lu, prominent positive Ce anomalies and negative Eu anomalies that are

Martin J Whitehouse; Balz S Kamber

2003-01-01

401

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

402

Rare earth elements in bottom sediments of major rivers around the Yellow Sea: implications for sediment provenance  

Microsoft Academic Search

Rare earth elements (REEs) of 91 fine-grained bottom sediment samples from five major rivers in Korea (the Han, Keum, and\\u000a Yeongsan) and China (the Changjiang and Huanghe) were studied to investigate their potential as source indicator for Yellow\\u000a Sea shelf sediments, this being the first synthetic report on REE trends for bottom sediments of these rivers. The results\\u000a show distinct

Zhaokai Xu; Dhongil Lim; Jinyong Choi; Shouye Yang; Hoisoo Jung

2009-01-01

403

Application of bromine trifluoride for pre-concentration and determination of rare-earth elements in fuel uranium dioxide  

Microsoft Academic Search

Radioactive indicator's (152Eu) method was used to study the behavior of rare-earth element (REE) micro-impurities at fluorination of fuel UO2 with bromine trifluoride. The proposed process is very simple and carried out under a blanket layer of Freon-113 in the glassy carbon (vitreous) crucibles.It was shown that uranium matrix completely removes from reaction sphere in the form of UF6 and

V. N. Mitkin; B. M. Shavinsky

2009-01-01

404

Partition coefficients of rare-earth elements between igneous matrix material and rock-forming mineral phenocrysts--II  

Microsoft Academic Search

Solid-liquid partition coefficients between phenocrysts and the host lavas have been measured for rare-earth elements by an isotope dilution technique. Phenocrysts analyzed include clinopyroxenes, orthopyroxenes, olivines, micas, amphiboles, garnet, plagioclases and K-feldspar. The consistency of much of the data suggests that most of the phenocrysts crystallized under equilibrium, or quasi-equilibrium, conditions. There is sufficient data on pyroxenes and feldspars to

C. C. Schnetzler; John A. Philpotts

1970-01-01

405

Dissolved indium and rare earth elements in three Japanese rivers and Tokyo Bay: Evidence for anthropogenic Gd and In  

Microsoft Academic Search

New data on the dissolved (<0.04 ?m) rare earth elements (REEs) and In in the Japanese Ara, Tama, and Tone river-estuaries and Tokyo Bay are presented. Unique shale-normalized REE patterns with a distinct positive Gd anomalies and a strong heavy-REE enrichment were seen throughout the data. The dissolved Gd anomaly is caused by local anthropogenic input mainly due to recent

Yoshiyuki Nozaki; Dorte Lerche; Dia Sotto Alibo; Makoto Tsutsumi

2000-01-01

406

Stable isotope and Rare Earth Element evidence for recent ironstone pods within the Archean Barberton greenstone belt, South Africa  

Microsoft Academic Search

There is considerable debate about the mode and age of formation of large (up to ?200m long) hematite and goethite ironstone bodies within the 3.2 to 3.5 Ga Barberton greenstone belt. We examined oxygen and hydrogen isotopes and Rare Earth Element (REE) concentrations of goethite and hematite components of the ironstones to determine whether these deposits reflect formation from sea-floor

Michael T. Hren; Donald R. Lowe; Michael M. Tice; Gary Byerly; C. Page Chamberlain

2006-01-01

407

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

Microsoft Academic Search

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,

Boris N. Zaitsev; Vyacheslav M. Esimantovskiy; Leonard N. Lazarev; Evgeniy G. Dzekun; Valeriy N. Romanovskiy; Terry A. Todd; Ken N. Brewer; Ronald S. Herbst; Jack D. Law

2001-01-01

408

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

409

Rare Earth Element Patterns in the Karst Terrains of Guizhou Province, China: Implication for Water\\/Particle Interaction  

Microsoft Academic Search

The authors determine the concentrations of dissolved (<0.22 ?m) rare earth elements (REE) and suspended particulate matter\\u000a (SPM) of typical karst rivers in Guizhou Province, China during the high-flow period. The concentrations of acid-soluble REE\\u000a extracted from SPM using diluted hydrochloric acid are also obtained to investigate water\\/particle interaction in the river\\u000a water. The dissolved REE contents in the river water

Guilin Han; Zhifang Xu; Yang Tang; Guoping Zhang

2009-01-01

410

Extraction of transplutionium and rare-earth elements, molybdenum and iron with zirconium salt of dibutyl phosphoric acid  

Microsoft Academic Search

Zirconium salt of dibutyl phosphoric acid (ZS-HDBP) dissolved in dilute tributyl phosphate (TBP) is proposed as a solvent\\u000a for separation of transplutonium and rare-earth elements (TPE, RE), including yttrium, from high-level waste in the presence\\u000a of molybdenum and iron. The optimum HDBP:Zr ratio is 9 for RE and TPE extraction and is 12.5 for Mo. IR spectra indicate formation\\u000a of

B. Ya. Zilberman; Yu. S. Fedorov; O. V. Shmidt; N. D. Goletsky; S. Yu. Sukhareva; E. A. Puzikov; D. N. Suglobov; L. G. Mashirov; G. R. Choppin

2003-01-01

411

Determination of rare earth elements in environmental matrices by sector-field inductively coupled plasma mass spectrometry  

Microsoft Academic Search

In the framework of an international certification campaign, sector-field inductively coupled plasma mass spectrometry (sector-field\\u000a ICP–MS) was used for the accurate determination of the rare earth elements in five candidate reference materials: aquatic\\u000a plant, calcareous soil, mussel tissue, river sediment, and tuna muscle. All samples were taken into solution by use of microwave-assisted\\u000a or mixed microwave-assisted \\/ open beaker acid

Jörgen Riondato; Frank Vanhaecke; Luc Moens; Richard Dams

2001-01-01

412

Analysis of the electronic dipole polarizability of ions in cubic oxides, fluorides, and sulfides of alkaline earth elements  

SciTech Connect

A new approach to calculating the electronic dipole polarizability of ions in crystals which is based on an analysis of the relationship between the electronic dipole polarizability of ion and its effective charge has been proposed. It is shown that applying this method to simple cubic oxides, fluorides, and sulfides of alkaline earth elements yields makes the calculation results consistent with the well-known data on the structure and type of bonds in these compounds.

Yatsenko, A. V., E-mail: lab2@crimea.edu [Taurida National University (Ukraine)

2010-07-15

413

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

414

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

PubMed

Stream waters draining an old mining area present very high rare earth element (REE) contents, reaching 928 microg/l as the maximum total value (sigmaREE). 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 the Fenice Capanne Mine (FCM), the most important base metal mine of the study area, the REE source coincides with the mine tailings, mostly the oldest ones composed of iron-rich materials. The geochemical history of the REEs released into Noni stream from wastes in the FCM area is strictly determined by the pH, which controls the REE speciation and in-stream processes. The formation of Al-rich and mainly Fe-rich flocs effectively scavenges the REEs, which are readily and drastically removed from the solution when the pH approaches neutrality. Leaching experiments performed on flocs and waste materials demonstrate that Fe-oxides/oxyhydroxides play a key role in the release of lanthanide elements into stream waters. The origin of the "roof-shaped" REE distribution pattern as well as the peculiar geochemical behavior of some lanthanide elements in the aqueous system are discussed. PMID:11911532

Protano, G; Riccobono, F

2002-01-01

415

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

2012-05-07

416

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

Microsoft Academic Search

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

L. Greenland; J. F. Lovering

1966-01-01

417

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

418

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

Microsoft Academic Search

Major and trace element zonation patterns were determined in ultrahigh-pressure eclogite garnets from the Western Gneiss Region (Norway). All investigated garnets show multiple growth zones and preserve complex growth zonation patterns with respect to both major and rare earth elements (REE). Due to chemical differences of the host rocks two types of major element compositional zonation patterns occur: (1) abrupt,

Matthias Konrad-Schmolke; Thomas Zack; Patrick J. O'Brien; Dorrit E. Jacob

2008-01-01

419

LA-ICPMS Trace- and Rare-Earth Element Zoning in (Ultra)high-Pressure Eclogites of the Western Gneiss Region, Norway  

NASA Astrophysics Data System (ADS)

Laser-ablation inductively coupled plasma mass spectrometry was used to determine Lu, Hf, Sm and Nd zoning in garnets and pyroxenes from 5 (ultra)high-pressure eclogites from the Western Gneiss Region, Norway, to determine the significance of Sm/Nd and Lu/Hf ages for the same rocks. Garnets of the 3 lower temperature eclogites (700°C and ~2.0--2.5 GPa) are strongly zoned in Lu, with core concentrations > 3 times that of the rims. Sm shows more subdued zoning, reflecting the reduced partitioning of Sm into garnet compared to Lu. The profiles are bell-shaped, as expected for Rayleigh fractionation, indicating that they formed during growth. Garnets in two of the three samples are unzoned in major elements, reflecting the enhanced diffusivities of these elements compared to rare-earth elements. Clinopyroxenes are unzoned in major elements and Hf; Sm and Nd are unzoned in two of the three samples. The enhanced concentration of Lu in garnet cores---and the more subdued zoning in Sm---indicates that the Lu/Hf ages will be weighted towards the core age and the Sm/Nd ages will represent an `average' age. Geochronologic data obtained at UW, Madison (Kylander-Clark et al., 2005) show that this is indeed the case---the Lu/Hf ages are 10--15 Myr older than the Sm/Nd ages. Garnets and clinopyroxenes of two higher temperature eclogites (700--800°C and ~3 GPa) are unzoned in Lu, Hf, Sm and Nd, and major elements, indicating that they recrystallized at temperatures high enough for homogenization. If so, they should yield cooling ages that are younger than the growth ages of the lower temperature eclogites. Geochronologic data obtained at UW, Madison (Kylander-Clark et al., 2005) show that this also is true---the high-temperature ages are 20--30 Myr younger than the low-temperature ages.

Kylander-Clark, A. R.; Hacker, B. R.; Vervoort, J. D.

2005-12-01

420

Determination of Rare Earths and Other Trace Elements in Igneous Rocks by Instrumental Activation Analysis.  

National Technical Information Service (NTIS)

An introduction to the use of instrumental activation analysis for geochemical research is provided and the particular significance of rare earth abundances explained. Complete details are given of the experimental techniques used in the instrumental anal...

J. E. Whitley

1974-01-01

421

Mapping of rare earth elements in nuclear waste glass-ceramic using micro laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

A micro-LIBS system was set up based on a quadruple Nd:YAG laser at 266 nm coupled with a microscope. Elemental mapping was performed on a Mo-rich glass-ceramic sample containing CaMoO4 crystallites hundreds of microns in length and about 25 ?m in section diameter. The topography of single-shot laser-induced craters was characterized using an atomic force microscope (AFM), which revealed a crater size less than 7 ?m. Mappings of Mo, Ca, Sr, Al, Fe, Zr and rare earth elements such as Eu, Nd, Pr and La were undertaken. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was conducted to validate the micro-LIBS analysis. Principal components analysis calculation was used to investigate the correlation of elements in the two phases of glass-ceramic. Correlation between Ca, Sr, rare earth elements and Mo indicates their preferential incorporation into the calcium molybdate crystalline phase. Anti-correlation between Fe, Zr, Al and Mo revealed their affinity to the glass phase.

Wang, X.; Motto-Ros, V.; Panczer, G.; De Ligny, D.; Yu, J.; Benoit, J. M.; Dussossoy, J. L.; Peuget, S.

2013-09-01

422

Metal loading effect on rare earth element binding to humic acid: Experimental and modelling evidence  

NASA Astrophysics Data System (ADS)

The effect of metal loading on the binding of rare earth elements (REE) to humic acid (HA) was studied by combining ultrafiltration and Inductively Coupled Plasma Mass Spectrometry techniques. REE-HA complexation experiments were performed at pH 3 for REE/C molar ratios ranging from ca 4 × 10 -4 to 2.7 × 10 -2. Results show that the relative amount of REE bound to HA strongly increases with decreasing REE/C. A middle-REE (MREE) downward concavity is shown by patterns at high metal loading, whereas patterns at low metal loading display a regular increase from La to Lu. Humic Ion Model VI modelling are close to the experimental data variations, provided that (i) the ?LK 2 parameter (i.e. the Model VI parameter taken into account the presence of strong but low density binding sites) is allowed to increase regularly from La to Lu (from 1.1 to 2.1) and (ii) the published log KMA values (i.e. the REE-HA binding constants specific to Model VI) are slightly modified, in particular with respect to heavy REE. Modelling approach provided evidence that logKdREE patterns with varying REE/C likely arises because REE binding to HA occurs through two types of binding sites in different density: (i) a few strong sites that preferentially complex the heavy REE and thus control the logKdREE atterns at low REE/C; (ii) a larger amount of weaker binding sites that preferentially complex the middle-REE and thus control the logKdREE pattern at high REE/C. Hence, metal loading exerts a major effect on HA-mediated REE binding, which could explain the diversity of published conditional constants for REE binding with HA. A literature survey suggests that the few strong sites activated at low REE/C could be multidentate carboxylic sites, or perhaps N-, or P-functional groups. Finally, an examination of the literature field data proposed that the described loading effect could account for much of the variation in REE patterns observed in natural organic-rich waters (DOC > 5 mg L -1 and 4 ? pH ? 7).

Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

2010-03-01

423

Robust elements of Snowball Earth atmospheric circulation and oases for life  

NASA Astrophysics Data System (ADS)

Atmospheric circulation in a Snowball Earth is critical for determining cloud behavior, heat export from the tropics, regions of bare ice, and sea glacier flow. These processes strongly affect Snowball Earth deglaciation and the ability of oases to support photosynthetic marine life throughout a Snowball Earth. Here we establish robust aspects of the Snowball Earth atmospheric circulation by running six general circulation models with consistent Snowball Earth boundary conditions. The models produce qualitatively similar patterns of atmospheric circulation and precipitation minus evaporation. The strength of the Snowball Hadley circulation is roughly double modern at low CO2 and greatly increases as CO2 is increased. We force a 1?D axisymmetric sea glacier model with general circulation model (GCM) output and show that, neglecting zonal asymmetry, sea glaciers would limit ice thickness variations to O(10%). Global mean ice thickness in the 1?D sea glacier model is well?approximated by a 0?D ice thickness model with global mean surface temperature as the upper boundary condition. We then show that a thin?ice Snowball solution is possible in the axysymmetric sea glacier model when forced by output from all the GCMs if we use ice optical properties that favor the thin?ice solution. Finally, we examine Snowball oases for life using analytical models forced by the GCM output and find that conditions become more favorable for oases as the Snowball warms, so that the most critical time for the survival of life would be near the beginning of a Snowball Earth episode.

Abbot, Dorian S.; Voigt, Aiko; Li, Dawei; Le Hir, Guillaume; Pierrehumbert, Raymond T.; Branson, Mark; Pollard, David; Koll, Daniel D. B.

2013-06-01

424

Post-assembly magnetization of rare-earth fractional-slot permanent-magnet machines using a Two-Shot Method  

Microsoft Academic Search

This paper studies the post-assembly magnetization of a fractional-slot brushless rare-earth surface permanent-magnet machine with six rotor poles and nine stator slots. In the paper, the simulation method is discussed and it is illustrated that it is possible to fully magnetize the machine after assembly using two pulses of the winding (“Two-Shot Method”) with a rotation of the rotor between

Min-Fu Hsieh; Yao-Min Lien; D. G. Dorrell

2010-01-01

425

Scavenging of dissolved yttrium and rare earths by precipitating iron oxyhydroxide: experimental evidence for Ce oxidation, Y-Ho fractionation, and lanthanide tetrad effect  

Microsoft Academic Search

Scavenging experiments were performed at pH 3.6 to 6.2 with synthetic solutions containing dissolved Fe (?7 mg\\/L), Rare Earths and Yttrium (?REY: ?61 ?g\\/L) in a matrix of 0.01 M HCl, and with natural water from Nishiki-numa spring, Japan, with the aim to study the fractionation that results from the interaction of dissolved REY with precipitating Fe oxyhydroxide. All patterns

Michael Bau

1999-01-01

426

Controls on the fractionation of isovalent trace elements in magmatic and aqueous systems: evidence from Y\\/Ho, Zr\\/Hf, and lanthanide tetrad effect  

Microsoft Academic Search

The parameters which control the behaviour of isovalent trace elements in magmatic and aqueous systems have been investigated\\u000a by studying the distribution of yttrium, rare-earth elements (REEs), zirconium, and hafnium. If a geochemical system is characterized\\u000a by CHArge-and-RAdius-Controlled (CHARAC) trace element behaviour, elements of similar charge and radius, such as the Y-Ho and Zr-Hf twin pairs, should display extremely\\u000a coherent

Michael Bau

1996-01-01

427