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1

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

Microsoft Academic Search

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

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

1989-01-01

2

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

3

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

E-print Network

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

Chakhmouradian, Anton

4

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

NASA Astrophysics Data System (ADS)

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

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

1989-06-01

5

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

Microsoft Academic Search

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

John S. Pallister; Roy J. Knight

1981-01-01

6

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

Microsoft Academic Search

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

John S. Pallister; Roy J. Knight

1981-01-01

7

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

8

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

Microsoft Academic Search

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

R. C. Price; S. R. Taylor

1973-01-01

9

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

USGS Publications Warehouse

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

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

2007-01-01

10

Rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments  

NASA Astrophysics Data System (ADS)

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

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

1981-04-01

11

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

SciTech Connect

Massive sulfide-sulfate deposits on the Southern Explorer Ridge were analyzed for 14 rare earth elements (REE) by a modified inductively coupled plasma-mass spectrometric technique that included a correction for high Ba content. Bulk samples of finely intermixed sulfides, sulfate, and amorphous silica contain {Sigma}REE concentrations of {le} 6 ppm. REE patterns range from (1) strongly enriched in light REE with positive Eu anomalies, to (2) relatively flat with positive Eu anomalies and slightly negative Ce anomalies, to (3) slightly enriched in light REE with moderately negative Ce anomalies. Pattern 1 is similar to that of 300-350 C solutions discharging at vents on the East Pacific Rise and the Mid-Atlantic Ridge, whereas pattern 3 resembles REE distributions in normal oceanic bottom waters. The sulfide-sulfate patterns are interpreted to result from variable mixtures of hydrothermal and normal seawater. Barite in gossans capping the mounds has an REE pattern almost identical to patterns of high-temperature vent solutions. Hydrothermal barite has lower REE contents and a different REE pattern relative to hydrogenous barite formed slowly on the sea floor.

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

1990-07-01

12

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

13

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

14

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

NASA Astrophysics Data System (ADS)

A twelve cruise time-series study of a seasonally anoxic basin in Chesapeake Bay was carried out between February 1988 and February 1989. Data from filtered bottom water and upper (0-1 cm) porewater samples are presented. This is the first study in which time-series measurements have been employed to understand the low temperature geochemistry of rare earth elements (REEs). The focus is on the coupling between REDOX (Reduction-Oxidation) variations and REE cycling, fractionation of trivalent REEs and development of cerium anomalies. The time-series results demonstrate that REEs have large seasonal cycles in both the water column and porewaters in response to the development of anoxia in the spring and reoxygenation in the fall. The transition from oxic to suboxic to anoxic conditions results in the release of REEs into the upper porewaters and bottom waters. The release of REEs and Fe are coincident in the bottom waters, while the release of REEs lags Fe by approximately 50 days in the upper porewaters. This decoupling is explained in terms of a REDOX front which moves upward from the sediments to bottom waters during the development of seasonal anoxia. The release of REEs to the upper porewaters and bottom water are accompanied by (1) fractionation across the trivalent REE series and by (2) the preferential input of Ce relative to its trivalent-only REE neighbors. REE (III) fractionation is such that the relative rate of release increases from Lu to La (light REE > middleREE > heavyREE). During reoxygenation, removal of dissolved REEs occurs from both the water column and upper porewaters and follows the same relative rates, LREE > MREE > HREE. Cerium removal occurs faster than its neighbor REE(III), indicating a rapid oxidation of Ce(III) to Ce(IV).

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

1992-09-01

15

Earth and Space Sciences Geochemistry 111  

E-print Network

Earth and Space Sciences #12;Geochemistry 111 5 Earth and Space Sciences Research in the realm of Earth and Space Sci- ences focusses on the observation and qualitative and quantitative description of natural phenom- ena on Earth and in the Universe, on the detailed study and experimental and computational

Henkel, Werner

16

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

NASA Astrophysics Data System (ADS)

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

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

2000-01-01

17

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

SciTech Connect

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

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

2000-01-01

18

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

Microsoft Academic Search

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

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

1999-01-01

19

Rare-earth element geochemistry of Colour Lake, an acidic freshwater lake on Axel Heiberg Island, Northwest Territories, Canada  

Microsoft Academic Search

A lake column profile was collected in 24 m of water from Colour Lake, Axel Heiberg Island, Northwest Territories, Canada, in early June of 1991 beneath 1.8 m of lake-ice. The rare-earth element (REE) concentrations of the acidic, fresh waters of Colour Lake were analyzed, along with the major solute chemistry, in order to investigate REE distribution and speciation in

Kevin H. Johannesson; W. Berry Lyons

1995-01-01

20

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

Microsoft Academic Search

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The 87Sr\\/86Sr ratios of the chimneys indicate that they have precipitated from

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

2000-01-01

21

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

23

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

USGS Publications Warehouse

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

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

1983-01-01

24

Early depositional history of metalliferous sediments in the Atlantis II Deep of the Red Sea: Evidence from rare earth element geochemistry  

NASA Astrophysics Data System (ADS)

The Atlantis II Deep is a brine-filled depression on the slowly spreading Red Sea rift axis. It is by far the largest deposit of hydrothermally precipitated metals on the present ocean floor and the only known modern deposit that is analogous to laminated Fe-rich chemical sediments, such as banded iron formation (BIF). The brine pool at the bottom of the Atlantis II Deep creates an environment where most of the hydrothermally sourced elements can be dispersed and deposited over an area of ˜60 km2. We analyzed the rare earth element concentrations in 100 small-volume samples from 9 cores in different parts of the Atlantis II Deep to better understand the origins of different types of metalliferous sediments (detrital, proximal hydrothermal and distal hydrothermal). Our results agree with earlier studies based on larger bulk samples that show the composition of the major depositional units is related to major changes in the location and intensity of hydrothermal activity and the amount of hydrothermal versus background sedimentation. In this paper, we address the origins of chemically distinct laminae (down to sub-millimeter) that correspond to ˜annual deposition. REE patterns clearly reflect 3 different sources (e.g., detrital, scavenging, direct hydrothermal input). Detrital REE that are delivered to the Deep from outside account for most of the REE in the sediments of the Atlantis II Deep, similar to BIF, and are unaffected by fractionation due to hydrothermal processes during deposition and diagenesis. Fe- and Mn-(oxy)hydroxides that form at the anoxic-oxic boundary scavenge REE from the brine pool as they settle. The Fe-(oxy)hydroxides contain a larger proportion of REE from seawater than any other sediment-type and also scavenge REE from pore waters after deposition. In contrast, the Mn-(oxy)hydroxides dissolve before deposition and thus function as transporting agents between seawater and the brine. However, there is little evidence for direct seawater influence in the REE geochemistry of the sediments (e.g., Y/Ho ratio). Non-ferrous sulfides form proximal to the hydrothermal vent source and inherit an hydrothermal REE pattern. The total REE content of the presently forming Fe-(oxy)hydroxides is very low due to limited input of REE into the brine. The largest proportion of non-detrital REE appears to have been deposited early in the history of the basin from an initial brine pool that was relatively enriched in REE, followed by a change in REE chemistry in later sediments. Similar abrupt changes in the REE chemistry of ancient chemical sediments may record similar processes, including changes in local basin evolution and input of REE from different sources.

Laurila, Tea E.; Hannington, Mark D.; Petersen, Sven; Garbe-Schönberg, Dieter

2014-02-01

25

The Medical Geochemistry of Dusts, Soils, and Other Earth Materials  

NASA Astrophysics Data System (ADS)

"Town clenched in suffocating grip of asbestos"USA Today, article on Libby,Montana, February, 2000"Researchers find volcanoes are bad for your health… long after they finish erupting"University of WarwickPress Release, 1999"Toxic soils plague city - arsenic, lead in 5 neighborhoods could imperil 17,000 residents"Denver Post, 2002"Ill winds - dust storms ferry toxic agents between countries and even continents"Science News, 2002A quick scan of newspapers, television, science magazines, or the internet on any given day has a fairly high likelihood of encountering a story (usually accompanied by a creative headline such as those above) regarding human health concerns linked to dusts, soils, or other earth materials. Many such concerns have been recognized and studied for decades, but new concerns arise regularly.Earth scientists have played significant roles in helping the medical community understand some important links between earth materials and human health, such as the role of asbestos mineralogy in disease (Skinner et al., 1988; Ross, 1999; Holland and Smith, 2001), and the role of dusts generated by the 1994 Northridge, California, earthquake in an outbreak of Valley Fever ( Jibson et al., 1998; Schneider et al., 1997).Earth science activities tied to health issues are growing (Skinner and Berger, 2003), and are commonly classified under the emerging discipline of medical geology (Finkelman et al., 2001; Selinus and Frank, 2000; Selinus, in press).Medical geochemistry (also referred to as environmental geochemistry and health: Smith and Huyck (1999), Appleton et al. (1996)) can be considered as a diverse subdiscipline of medical geology that deals with human and animal health in the context of the Earth's geochemical cycle ( Figure 1). Many medical geochemistry studies have focused on how chemical elements in rocks, soils, and sediments are transmitted via water or vegetation into the food chain, and how regional geochemical variations can result in disease clusters either through dietary deficiency of essential elements or dietary excess of toxic elements. (28K)Figure 1. Potential human exposure routes within the earth's geochemical cycle can come from a wide variety of both natural and anthropogenic sources. This chapter focuses on a somewhat narrower area of medical geochemistry: the study of mechanisms of uptake of earth materials by humans and animals and their reactions to these materials. In order for earth materials to affect health, they must first interact with the body across key interfaces such as the respiratory tract, gastrointestinal tract, skin, and eyes. In some way, all of these interfaces require the earth materials to interact chemically with water-based body fluids such as lung fluids, gastrointestinal fluids, saliva, or blood plasma.The primary goal of this chapter, co-authored by a geochemist and a toxicologist, is to provide both geochemists and scientists from health disciplines with an overview of the potential geochemical mechanisms by which earth materials can influence human health. It is clear that significant opportunities for advancement in this arena will require continued and increased research collaborations between geochemists and their counterparts in the health disciplines.

Plumlee, G. S.; Ziegler, T. L.

2003-12-01

26

Global Oceanic Basalt Geochemistry From EarthChem Databases  

NASA Astrophysics Data System (ADS)

For the past 21 years, global trace element systematics in oceanic basalts have been systematically developed, using mass spectrometry, by the MPI geochemistry department in Mainz, starting with Ba-Rb-Cs, and continuing with K-U-Th, Nb-U-Th, Pb-Ce, Pr-Mo, Nb-Ta, Sn-REE, Sb-REE, and Y-Ho relations. These were complemented by other groups, contributing e.g. Sr-REE relationships and more refined Nb-Ta systematics. Goal of these investigations was to establish relative trace element compatibilities during mantle melting, the corresponding enrichment and depletion patterns in MORB, OIB, subduction-related volcanics and the continental crust, and the relationships to Bulk Silicate Earth abundances through comparisons with element abundances in meteorites and in the continental crust (see e.g. [1]). Most of these studies were initially based on extremely limited data sets, often fewer than 100 analyses, because routine analytical techniques such as XRF and INAA were inadequate, either in sensitivity or accuracy or both, for many of the elements of interest. The advent of ICPMS technology has increased the volume of available, useable data enormously. The most recent development of laser source ICPMS is accelerating the acquisition of comprehensive trace element data even more dramatically. Although the general quality of recent trace element analyses has improved significantly, there remain large differences in reliability between published data because of varying analytical uncertainties and sample alteration. Thus, quality assurance remains an enormous task. In any case, now and in the foreseeable future, it will be impossible to assess global geochemical data without the use of comprehensive databases. Such databases are now available under http://www.earthchem.org/, comprising http://beta.petdb.ciesin.columbia.edu/; http://georoc.mpch-mainz.gwdg.de/, and http://navdat.geo.ku.edu/ . Unfortunately, the use of such databases is not without pitfalls. Often, appropriate metadata are inadequate or absent, and a significant fraction of the primary data and metadata contain errors, either in the original publication or in the transfer to the database. Therefore, analysis of these databases must be performed by experienced geochemists, who are best qualified to recognize erroneous or low-quality data. Even so, elimination of such erroneous or poor data frequently requires subjective judgment. Such evaluations should then produce "expert data sets", which can subsequently be used by non-experts, including non-specialist geochemists, geophysicists, and geologists. A partial expert evaluation of global MORB geochemistry has been prepared by Su [2], who gives segment-by-segment MORB averages. We are preparing an expert data set for global trace element and isotope geochemistry of ocean island basalts. On the basis of these data, we reevaluate global compatibility relationships. At this stage, these relationships are remarkably similar to those summarized by Hofmann [3], and by Sun and McDonough [4], using extremely limited data. This validates the original methodology used by these authors. At the same time, basalt suites containing geochemical anomalies can now be more clearly delineated. Thus, EarthChem databases allow us to develop a comprehensive view of global chemical differentiation of the Earth. [1] Hofmann, A.W. (2003) in Treatise on Geochemistry, ed. R.W. Carlson, Vol.2, 61-101. [2] Su,, Y.J. (2002) PhD Thesis, Columbia University, 472p. [3] Hofmann, A.W. (1988) Earth Planet. Sci. Lett. 90, 297-314. [4] Sun, S.-S. & McDonough, W.F. (1989) Geol. Soc. Spec. Publ. 42 (eds. A.D. Saunders & M.J. Norry), 313-345.

Hofmann, A. W.; Sarbas, B.; Jochum, K. P.; Stracke, A.

2004-12-01

27

12.479 Trace-Element Geochemistry, Fall 2006  

E-print Network

Focuses on element distribution in rocks and minerals using data obtained from natural and experimental systems. Emphasizes models describing trace-element partitioning and applications of trace-element geochemistry to ...

Frey, Frederick August

28

12.479 Trace-Element Geochemistry, Spring 2009  

E-print Network

The emphasis of this course is to use Trace Element Geochemistry to understand the origin and evolution of igneous rocks. The approach is to discuss the parameters that control partitioning of trace elements between phases ...

Frey, Frederick

29

Geochemistry of the Solid Earth I: The Mantle and Core  

NSDL National Science Digital Library

This site is a chapter from a book on geochemistry by Dr. W. M. White that is used in a geochemistry course at Cornell University. The 39-page PDF document discusses the composition and evolution of the mantle and core of the earth, and the geochemical methods used to make these determinations. Additional topics include phase transitions, the primitive mantle, differentiation of the mantle, mantle geochemical reservoirs, and evolution of the depleted upper mantle and mantle plume reservoirs. Problems and figures accompany the text.

White, William M.; Department Of Earth And Atmospheric Science, Cornell U.

30

Trace element geochemistry of river sediment, Orissa State, India  

E-print Network

Trace element geochemistry of river sediment, Orissa State, India K.O. Konhausera , M.A. Powellb analyses of bottom sediment from rivers flowing through Orissa State, India indi- cated that trace element% of the allochthonous sediments (Subramanian, 1979). In contrast, the major southern Peninsular rivers (i.e. Krishna

Konhauser, Kurt

31

Fluid inclusion, rare earth element geochemistry, and isotopic characteristics of the eastern ore zone of the Baiyangping polymetallic Ore district, northwestern Yunnan Province, China  

NASA Astrophysics Data System (ADS)

The Baiyangping Cu-Ag polymetallic ore district is located in the northern part of the Lanping-Simao foreland fold belt, which lies between the Jinshajiang-Ailaoshan and Lancangjiang faults in western Yunnan Province, China. The source of ore-forming fluids and materials within the eastern ore zone were investigated using fluid inclusion, rare earth element (REE), and isotopic (C, O, and S) analyses undertaken on sulfides, gangue minerals, wall rocks, and ores formed during the hydrothermal stage of mineralization. These analyses indicate: (1) The presence of five types of fluid inclusion, which contain various combinations of liquid (l) and vapor (v) phases at room temperature: (a) H2O (l), (b) H2O (l) + H2O (v), (c) H2O (v), (d) CmHn (v), and (e) H2O (l) + CO2 (l), sometimes with CO2 (v). These inclusions have salinities of 1.4-19.9 wt.% NaCl equivalents, with two modes at approximately 5-10 and 16-21 wt.% NaCl equivalent, and homogenization temperatures between 101 °C and 295 °C. Five components were identified in fluid inclusions using Raman microspectrometry: H2O, dolomite, calcite, CH4, and N2. (2) Calcite, dolomitized limestone, and dolomite contain total REE concentrations of 3.10-38.93 ppm, whereas wall rocks and ores contain REE concentrations of 1.21-196 ppm. Dolomitized limestone, dolomite, wall rock, and ore samples have similar chondrite-normalized REE patterns, with ores in the Huachangshan, Xiaquwu, and Dongzhiyan ore blocks having large negative ?Ce and ?Eu anomalies, which may be indicative of a change in redox conditions during fluid ascent, migration, and/or cooling. (3) ?34S values for sphalerite, galena, pyrite, and tetrahedrite sulfide samples range from -7.3‰ to 2.1‰, a wide range that indicates multiple sulfur sources. The basin contains numerous sources of S, and deriving S from a mixture of these sources could have yielded these near-zero values, either by mixing of S from different sources, or by changes in the geological conditions of seawater sulfate reduction to sulfur. (4) The C-O isotopic analyses yield ?13C values from ca. zero to -10‰, and a wider range of ?18O values from ca. +6 to +24‰, suggestive of mixing between mantle-derived magma and marine carbonate sources during the evolution of ore-forming fluids, although potential contributions from organic carbon and basinal brine sources should also be considered. These data indicate that ore-forming fluids were derived from a mixture of organism, basinal brine, and mantle-derived magma sources, and as such, the eastern ore zone of the Baiyangping polymetallic ore deposit should be classified as a “Lanping-type” ore deposit.

Feng, Caixia; Bi, Xianwu; Liu, Shen; Hu, Ruizhong

2014-05-01

32

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

E-print Network

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

Wehrli, Bernhard

33

Trace element geochemistry of CR chondrite metal  

E-print Network

We report trace element analyses by laser ablation inductively coupled plasma mass spectrometry of metal grains from 9 different CR chondrites, distinguishing grains from chondrule interior ("interior grains"), chondrule surficial shells ("margin grains") and the matrix ("isolated grains"). Save for a few anomalous grains, Ni-normalized trace element patterns are similar for all three petrographical settings, with largely unfractionated refractory siderophile elements and depleted volatile Au, Cu, Ag, S. All types of grains are interpreted to derive from a common precursor approximated by the least melted, fine-grained objects in CR chondrites. This also excludes recondensation of metal vapor as the origin of the bulk of margin grains. The metal precursors presumably formed by incomplete condensation, with evidence for high-temperature isolation of refractory platinum-group-element (PGE)-rich condensates before mixing with lower temperature PGE-depleted condensates. The rounded shape of the Ni-rich, interior ...

Jacquet, Emmanuel; Alard, Olivier; Kearsley, Anton T; Gounelle, Matthieu

2015-01-01

34

Trace element geochemistry of CR chondrite metal  

NASA Astrophysics Data System (ADS)

We report trace element analyses by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of metal grains from nine different CR chondrites, distinguishing grains from chondrule interior ("interior grains"), chondrule surficial shells ("margin grains"), and the matrix ("isolated grains"). Save for a few anomalous grains, Ni-normalized trace element patterns are similar for all three petrographic settings, with largely unfractionated refractory siderophile elements and depleted volatile Au, Cu, Ag, S. All three types of grains are interpreted to derive from a common precursor approximated by the least-melted, fine-grained objects in CR chondrites. This also excludes recondensation of metal vapor as the origin of the bulk of margin grains. The metal precursors were presumably formed by incomplete condensation, with evidence for high-temperature isolation of refractory platinum-group-element (PGE)-rich condensates before mixing with lower temperature PGE-depleted condensates. The rounded shape of the Ni-rich, interior grains shows that they were molten and that they equilibrated with silicates upon slow cooling (1-100 K h-1), largely by oxidation/evaporation of Fe, hence their high Pd content, for example. We propose that Ni-poorer, amoeboid margin grains, often included in the pyroxene-rich periphery common to type I chondrules, result from less intense processing of a rim accreted onto the chondrule subsequent to the melting event recorded by the interior grains. This means either that there were two separate heating events, which formed olivine/interior grains and pyroxene/margin grains, respectively, between which dust was accreted around the chondrule, or that there was a single high-temperature event, of which the chondrule margin records a late "quenching phase," in which case dust accreted onto chondrules while they were molten. In the latter case, high dust concentrations in the chondrule-forming region (at least three orders of magnitude above minimum mass solar nebula models) are indicated.

Jacquet, Emmanuel; Paulhiac-Pison, Marine; Alard, Olivier; Kearsley, Anton T.; Gounelle, Matthieu

2013-10-01

35

DALHOUSIE UNIVERSITY, DEPARTMENT OF EARTH SCIENCES Assistant Professor -Geophysics, Sedimentology, or Geochemistry  

E-print Network

DALHOUSIE UNIVERSITY, DEPARTMENT OF EARTH SCIENCES Assistant Professor - Geophysics, Sedimentology, or Geochemistry The Department of Earth Sciences at Dalhousie University invites applications for a faculty research projects. Essential qualifications include a Ph.D. in Earth Sciences or closely related field

Brownstone, Rob

36

Tungsten geochemistry and implications for understanding the Earth's interior  

NASA Astrophysics Data System (ADS)

The concentration of tungsten (W) in basaltic melts provides a window into the behavior of this element during core-mantle separation, crust formation, silicate differentiation, and potentially core-mantle interaction. We have analyzed an extensive suite of modern basalts ( n = 86) for their trace element chemistry via laser ablation ICP-MS, with barium (Ba), thorium (Th), uranium (U), and W concentrations typically determined to ? 5% (2 ?) uncertainty. We find that the partitioning behavior of U mirrors that of W during basalt genesis, whereas Ba and Th both behave more incompatibly. The W/U ratio of our complete sample suite (0.65 ± 0.45, 2 ?) is representative of the mean modern mantle, and is indistinguishable from that of mid-ocean ridge basalts (W/U MORB = 0.65 ± 0.41, n = 52), ocean island basalts (W/U OIB = 0.63 ± 0.07, n = 10), and back-arc basin basalts (W/U BABB = 0.62 ± 0.09, n = 12). This ratio is also consistent with the W/U ratio of the continental crust, and thus represents the W/U ratio of the entire silicate portion of the Earth. Assuming a concentration of 20 ± 8 (2 ?) ng/g U in the bulk silicate Earth, the abundance of W in the silicate Earth is 13 ± 10 ng/g. Following mass balance, this implies a mean modern mantle and core composition of 8.3 ± 7.1 ng/g W and 500 ± 120 ng/g W, respectively. Additionally, the MORB source is modeled to contain approximately 3.0 ± 2.3 ng/g W, indicating a four-fold depletion of the highly incompatible elements in the MORB source relative to the silicate Earth. Although both the isotopic composition of W and the constancy of the silicate Earth W/U ratio allow for potential insight into core-mantle exchange, both of these proxies are extremely dependent on the chemical composition of the source. A case study of three Hawaiian picrites with enrichments in 186Os- 187Os but terrestrial ?182W can be explained by: i) a lack of a core component in the Hawaiian "plume," ii) crustal contamination, or iii) a source composition enriched in incompatible trace elements relative to the bulk silicate Earth.

Arevalo, Ricardo; McDonough, William F.

2008-08-01

37

Trace- and rare-earth element geochemistry and Pb-Pb dating of black shales and intercalated Ni-Mo-PGE-Au sulfide ores in Lower Cambrian strata, Yangtze Platform, South China  

NASA Astrophysics Data System (ADS)

The Lower Cambrian black shale sequence of the Niutitang Formation in the Yangtze Platform, South China, hosts an extreme metal-enriched sulfide ore bed that shows >10,000 times enrichment in Mo, Ni, Se, Re, Os, As, Hg, and Sb and >1,000 times enrichment in Ag, Au, Pt, and Pd, when compared to average upper continental crust. We report in this paper trace- and rare-earth-element concentrations and Pb-Pb isotope dating for the Ni-Mo-PGE-Au sulfide ores and their host black shales. Both the sulfide ores and their host black shales show similar trace-element distribution patterns with pronounced depletion in Th, Nb, Hf, Zr, and Ti, and extreme enrichment in U, Ni, Mo, and V compared to average upper crust. The high-field-strength elements, such as Zr, Hf, Nb, Ta, Sc, Th, rare-earth elements, Rb, and Ga, show significant inter-element correlations and may have been derived mainly from terrigenous sources. The redox sensitive elements, such as V, Ni, Mo, U, and Mn; base metals, such as Cu, Zn, and Pb; and Sr and Ba may have been derived from mixing of seawater and venting hydrothermal sources. The chondrite-normalized REE patterns, positive Eu and Y anomalies, and high Y/Ho ratios for the Ni-Mo-PGE-Au sulfide ores are also suggestive for their submarine hydrothermal-exhalative origin. A stepwise acid-leaching Pb-Pb isotope analytical technique has been employed for the Niutitang black shales and the Ni-Mo-PGE-Au sulfide ores, and two Pb-Pb isochron ages have been obtained for the black shales (531±24 Ma) and for the Ni-Mo-PGE-Au sulfide ores (521±54 Ma), respectively, which are identical and overlap within uncertainty, and are in good agreement with previously obtained ages for presumed age-equivalent strata.

Jiang, Shao-Yong; Chen, Yong-Quan; Ling, Hong-Fei; Yang, Jing-Hong; Feng, Hong-Zhen; Ni, Pei

2006-08-01

38

Author's personal copy Tungsten geochemistry and implications for understanding the Earth's interior  

E-print Network

Author's personal copy Tungsten geochemistry and implications for understanding the Earth Keywords: tungsten uranium basalt core mantle concentration ratio The concentration of tungsten (W of tungsten (W) was sequestered into the core (Jagoutz et al., 1979; Sun, 1982; Newsom and Palme, 1984

Mcdonough, William F.

39

Tracking Iceland Plume Motion Using Trace Element Geochemistry  

NASA Astrophysics Data System (ADS)

The Greenland-Scotland Ridge (GSR) is a hotspot track built by interaction between the Mid Atlantic Ridge (MAR) and the Iceland mantle plume. Unlike most other hotspot tracks built by ridge-plume interaction, the GSR is 2 to 3 times wider than the plume conduit in the upper mantle. (This unusual wide morphology arises because Icelandic crust changes significantly in thickness within a few million years of accretion, probably mainly by viscous flow in the hot lower crust). The upshot is that the GSR cannot be compared directly with theoretical plume tracks from hotspot reference frame models. However, it is possible to track the position of the Iceland plume conduit using the trace element geochemistry of basaltic lavas. Away from the plume conduit, plate spreading drives upwelling of mantle through the melting region. Above the plume conduit, plume-driven flow forces mantle through the lower part of the melting region faster than the plate-driven upwelling rate. The average depth of melting is therefore greater directly above the plume conduit than away from the plume conduit, and this difference in average melting depth means that melts generated directly above the plume conduit are relatively enriched in incompatible trace elements. Joint modelling of trace element compositions and crustal thickness can also be used to establish location of melting relative to the plume conduit. To date, these concepts have been used only to explain compositional variations in modern (post-glacial) Icelandic lavas; in this study we show that the same concepts can be applied to map the location of the plume conduit throughout the onshore Icelandic geological record (since the middle Miocene, c. 16 Ma). The plume track thus determined is in reasonable agreement with theoretical tracks calculated under the assumption that the Iceland Plume has remained fixed relative to other Indo-Atlantic hotspots. This result also supports the idea that episodic relocations of the onshore part of the MAR act to maintain the spreading axis above the plume conduit.

Fitton, J. G.; Walters, R. L.; Jones, S. M.

2011-12-01

40

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

41

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

42

Rare Earth Elements in the Whitestone Anorthosite.  

E-print Network

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

Barker, Franklin James

1972-01-01

43

Trace element geochemistry: New technology for stratigraphic correlations and formation evaluation  

Microsoft Academic Search

New technology based on the trace element chemistry of rocks is being developed as a tool for mapping subsurface formations in oilfields. This technology can be used to map rock formations in areas where traditional techniques are inconclusive. Trace element geochemistry complements and enhances conventional tools such as biostratigraphy, petrology, and log analysis. Applications cover a broad array of topics

Charles J. Lord

1995-01-01

44

Rare Earth Element Mines, Deposits, and Occurrences  

E-print Network

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

Torgersen, Christian

45

The geochemistry of carbonatites revisited: Two major types of continental carbonatites and their trace-element signatures  

NASA Astrophysics Data System (ADS)

There have been several attempts to systematize the geochemistry of carbonatites, most recently by Samoilov (1984), Nelson et al. (1988), Woolley and Kempe (1989), and Rass (1998). These studies revealed a number of important geochemical characteristics that can be used to track the evolutionary history of these rocks, distinguish them from modally similar metamorphic parageneses, and aid in mineral exploration for rare earths, niobium and other resources commonly associated with carbonatites. Important breakthroughs in the understanding of carbonatite petrogenesis and numerous reports of new carbonatite localities made in the past two decades lay the ground for a critical re-assessment of the geochemistry of these rocks. A new representative database of whole-rock carbonatite analyses was compiled from the post-1988 literature and various unpublished sources. The database contains 820 analyses encompassing calcio-, magnesio- and ferrocarbonatites from 174 localities (ca. one-third of the total number of carbonatites known worldwide) reduced to ca. 350 analyses following the approach of Woolley and Kempe (1989). Carbonatites emplaced in oceanic settings (e.g., Cape Verde), ophiolite belts (e.g., Oman), or those of uncertain tectonic affinity (e.g., El Picacho in Mexico) were not included. Two major types of continental carbonatites can be distinguished on the basis of their geological setting and trace-element geochemistry: (1) carbonatites emplaced in rifts and smaller-scale extensional structures developed in stable Archean cratons or paleo-orogenic belts, and (2) carbonatites emplaced in collisional settings following the orogenesis. In both settings, the most common and best-studied type of carbonatite is calcite carbonatite (predominantly intrusive with a small percentage of extrusive occurrences), which accounts for 62% of the analyses included in the database. Both types of carbonatite are typically associated with alkaline silicate lithologies (meleigites, nepheline syenites, etc.), but those associated with type-1 rocks are typically Na-rich and silica-undersaturated, whereas type-2 carbonatites are associated with K-rich silica-saturated to undersaturated syenites. Type-1 carbonatites are notably different from their type-2 counterparts in showing higher abundances of high-field-strength elements (HFSE = Ti, Zr, Hf, Nb, Ta), Rb, U and V, but lower levels of Sr, Ba, Pb, rare-earth elements, F and S. Key element ratios are also different in the two carbonatite types; in particular, Rb/K, Nb/Ta, Zr/Hf and Ga/Al values are consistently higher in type-1 samples. Notably, some element ratios (e.g., Co/Ni and Y/Ho) are very similar in both groups. Type-2 carbonatites commonly show a 13C-depleted signature relative to the "primary carbonatite" range (Deines, 1989). The observed differences in geological setting and geochemistry indicate the existence of two distinct carbonatite sources in the subcontinental lithosphere: amphibole-bearing lherzolite producing type-1 rocks (cf. Chakhmouradian, 2006), and subducted oceanic crust (rutile-bearing eclogite?) yielding type-2 melts depleted in HFSE, but enriched in light carbon, large-ion-incompatible elements, F and S. References: Chakhmouradian, A.R. (2006) High-field-strength elements in carbonatitic rocks: Geochemistry, crystal chemistry and significance for constraining the sources of carbonatites. Chem. Geol., 235, 138-160. Deines, P. (1989) Stable isotope variations in carbonatites. In: Carbonatites: Genesis and Evolution (K. Bell, Ed.). Unwin Hyman, London, 301-359. Nelson, D.R., Chivas, A.R., Chappell, B.V. and McCulloch, M.T. (1988) Geochemical and isotopic systematic in carbonatites and implications for the evolution of ocean-island sources. Geochim. Cosmochim. Acta, 52, 1-17. Rass, I.T. (1998) Geochemical features of carbonatite indicative of the composition, evolution, and differentiation of their mantle magmas. Geochem. Int., 36, 107-116. Samoilov, V.S. (1984) Geochemistry of Carbonatites. Nauka, Moscow (in Russ.). Woolley, A.R. and Kempe, D.R.C. (1989)

Chakhmouradian, A.

2009-04-01

46

Chondrule trace element geochemistry at the mineral scale  

E-print Network

We report trace element analyses from mineral phases in chondrules from carbonaceous chondrites (Vigarano, Renazzo and Acfer 187), carried out by laser ablation inductively coupled plasma mass spectrometry. Results are similar in all three meteorites. Mesostasis has Rare Earth Element (REE) concentrations of 10-20 x CI. Low-Ca pyroxene has light REE (LREE) concentrations near 0.1 x CI and heavy REE (HREE) near 1 x CI respectively. Olivine has HREE concentrations at 0.1-1 x CI and LREE around 10-2 x CI. The coarsest olivine crystals tend to have the most fractionated REE patterns, indicative of equilibrium partitioning. Low-Ca pyroxene in the most pyroxene-rich chondrules tends to have the lowest REE concentrations. Type I chondrules seem to have undergone a significant degree of batch crystallization (as opposed to fractional crystallization), which requires cooling rates slower than 1-100 K/h. This would fill the gap between igneous CAIs and type II chondrules. The anticorrelation between REE abundances and ...

Jacquet, Emmanuel; Gounelle, Matthieu

2015-01-01

47

Sedimentology, Geochemistry, and Geophysics of the Cambrian Earth System  

NASA Astrophysics Data System (ADS)

Within this dissertation, I document how—and hypothesize why—the quirks and qualities of the Cambrian Period demarcate this interval as fundamentally different from the preceding Proterozoic Eon and succeeding periods of the Phanerozoic Eon. To begin, I focus on the anomalous marine deposition of the mineral apatite. Sedimentary sequestration of phosphorus modulates the capacity for marine primary productivity and, thus, the redox state of the Earth system. Moreover, sedimentary apatite minerals may entomb and replicate skeletal and soft-tissue organisms, creating key aspects of the fossil record from which paleontologists deduce the trajectory of animal evolution. I ask what geochemical redox regime promoted the delivery of phosphorus to Cambrian seafloors and conclude that, for the case of the Thorntonia Limestone, apatite nucleation occurred under anoxic, ferruginous subsurface water masses. Moreover, I infer that phosphorus bound to iron minerals precipitated from the water column and organic-bound phosphorus were both important sources of phosphorus to the seafloor. Petrographic observations allow me to reconstruct the early diagenetic pathways that decoupled phosphorus from these delivery shuttles and promoted the precipitation of apatite within the skeletons of small animals. Together, mechanistic understandings of phosphorus delivery to, and retention within, seafloor sediment allow us to constrain hypotheses for the fleeting occurrence of widespread apatite deposition and exquisite fossil preservation within Cambrian sedimentary successions. Next, I describe and quantify the nature of carbonate production on a marine platform deposited at the hypothesized peak of Cambrian skeletal carbonate production. I find that fossils represent conspicuous, but volumetrically subordinate components of early Cambrian carbonate reef ecosystems and that despite the evolution of mineralized skeletons, Cambrian carbonate platforms appear similar to their Neoproterozoic counterparts, primarily reflecting abiotic and microbial deposition. Finally, I investigate the geodynamic mechanism responsible for rapid, oscillatory true polar wander (TPW) events proposed for the Neoproterozoic and Phanerozoic Earth on the basis of paleomagnetic data. Using geodynamic models, I demonstrate that elastic strength in the lithosphere and stable excess ellipticity of Earth's figure provided sufficient stabilization to return the pole to its original state subsequent to convectively-driven TPW.

Creveling, Jessica Renee

48

Building the EarthChem System for Advanced Data Management in Igneous Geochemistry  

NASA Astrophysics Data System (ADS)

Several mature databases of geochemical analyses for igneous rocks are now available over the Internet. The existence of these databases has revolutionized access to data for researchers and students allowing them to extract data sets customized to their specific problem from global data compilations with their desktop computer within a few minutes. Three of the database efforts - PetDB, GEOROC, and NAVDAT - have initiated a collaborative effort called EarthChem to create better and more advanced and integrated data management for igneous geochemistry. The EarthChem web site (http://www.earthchem.org/) serves as a portal to the three databases and information related to EarthChem activities. EarthChem participants agreed to establish a dialog to minimize duplication of effort and share useful tools and approaches. To initiate this dialog, a workshop was run by EarthChem in October, 2003 to discuss cyberinfrastructure needs in igneous geochemistry (workshop report available at the EarthChem site). EarthChem ran an information booth with database and visualization demonstrations at the Fall 2003 AGU meeting (and will have one in 2004) and participated in the May 2003 GERM meeting in Lyon, France where we provided the newly established Publishers' Round Table a list of minimum standards of data reporting to ease the assimilation of data into the databases. Aspects of these suggestions already have been incorporated into new data policies at Geochimica et Cosmochimica Acta and Chemical Geology (Goldstein et al. 2004), and are under study by the Geological Society of America. EarthChem presented its objectives and activities to the Solid Earth Sciences community at the Annual GSA Meeting 2003 (Lehnert et al, 2003). Future plans for EarthChem include expanding the types and amounts of data available from a single portal, giving researchers, faculty, students, and the general public the ability to search, visualize, and download geochemical and geochronological data for a wide variety of rock types of global distribution. We also hope to implement more mapping and query functions to open the application of these data across the spectrum of geoscientists. Lastly, we want to facilitate data submission and data entry in anticipation of incorporating more data directly from publishers and from a broader cross section of researchers. The building of interfaces for the transfer of raw and reduced data will allow data to be archived, and most importantly accessed, in a manner that will facilitate the use of geochemical data to address a wide variety of problems in the solid earth sciences.

Lehnert, K.; Walker, J. D.; Carlson, R. W.; Hofmann, A. W.; Sarbas, B.

2004-12-01

49

Strontium isotope geochemistry of alluvial groundwater: a tracer for groundwater resources characterisation Hydrology and Earth System Sciences, 8(5), 959972 (2004) EGU  

E-print Network

Strontium isotope geochemistry of alluvial groundwater: a tracer for groundwater resources characterisation 959 Hydrology and Earth System Sciences, 8(5), 959972 (2004) © EGU Strontium isotope geochemistry for corresponding author : p.negrel@brgm.fr Abstract This study presents strontium isotope and major ion data

Paris-Sud XI, Université de

50

What about the rare-earth elements  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

51

Rare earth element scavenging in seawater  

SciTech Connect

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

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

1990-10-01

52

Geochemistry of transition elements in garnet lherzolite nodules in kimberlites  

Microsoft Academic Search

The clinopyroxenes and garnets from garnet lherzolite nodules in kimberlites were analyzed for the major and trace elements (Sc, Ti, V, Cr, Mn, Co, Sr, and Zr) with the secondary ion mass spectrometry (SIMS) techniques using an ion-microprobe. The concentration ranges for clinopyroxenes are: 12–90 ppm Sc, 60–2540 ppm Ti, 110–350 ppm V, 2400 ppm-1.68% Cr, 470–1100 ppm Mn, 18–70

N. Shimizu; C. J. Allègre

1978-01-01

53

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

54

Nitrite complexes of the rare earth elements.  

PubMed

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

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

2014-03-21

55

Rare earth elements and permanent magnets (invited)  

NASA Astrophysics Data System (ADS)

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

Dent, Peter C.

2012-04-01

56

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

PubMed

We report a portable rare-earth element analyzer with a palm-top size chamber including the electron source of a pyroelectric crystal and the sample stage utilizing cathodoluminescence (CL) phenomenon. The portable rare-earth element analyzer utilizing CL phenomenon is the smallest reported so far. The portable rare-earth element analyzer detected the rare-earth elements Dy, Tb, Er, and Sm of ppm order in zircon, which were not detected by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. We also performed an elemental mapping of rare-earth elements by capturing a CL image using CCD camera. PMID:24387481

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

2013-12-01

57

Note: Portable rare-earth element analyzer using pyroelectric crystal  

SciTech Connect

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

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

2013-12-15

58

Note: Portable rare-earth element analyzer using pyroelectric crystal  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

59

Geochemistry of U and Th and its Influence on the Origin and Evolution of the Crust of Earth and the Biological Evolution  

E-print Network

We have investigated the migration behaviors of uranium (U) and thorium (Th) in Earth and other terrestrial planets. Theoretical models of U and Th migration have been proposed. These models suggest that the unique features of Earth are closely connected with its unique U and Th migration models and distribution patterns. In the Earth, U and Th can combine with oxidative volatile components and water, migrate up to the asthenosphere position to form an enrichment zone (EZ) of U and Th first, and then migrate up further to the crusts through magmatism and metamorphism. We emphasize that the formation of an EZ of U, Th and other heat-producing elements is a prerequisite for the formation of a plate tectonic system. The heat-producing elements, currently mainly U and Th, in the EZ are also the energy sources that drive the formation and evolution of the crust of Earth and create special granitic continental crusts. In other terrestrial planets, including Mercury, Venus, and Mars, an EZ can not be formed because of a lack of oxidative volatile components and water. For this reason, a plate tectonic system can not been developed in these planets. We also emphasize the influence of U and Th in EZ on the development and evolution of life on Earth. We propose that since the Earth and planets were born in a united solar system, there should be some common mechanisms to create the similarities and differences between them. We have tried to develop an integrated view to explain some problems in the tectonics of Earth and evolution, bio-evolution, and planetary dynamics through U and Th geochemistry. We believe that a comprehensive exploration on energy sources and their evolution is a good way to build bridges between different disciplines of science in order to better understand the Earth and planets.

Xuezhao Bao; Ali Zhang

2007-10-16

60

Principles of Geochemistry  

NASA Astrophysics Data System (ADS)

Geochemistry is one of those broad fields of study that is difficult to define to the satisfaction of all those who work in it. One widely accepted definition is the traditional Goldschmidtian approach that considers geochemistry to be a study of the geological and chemical controls on the distribution of the elements within the earth. This is the definition of geochemistry that is implicit in the approach taken by this book. On the whole, the book does a commendable job in treating this aspect of geochemistry, although the quality of coverage for various subjects is far from uniform. For instance, the treatment of the distribution of major and trace elements caused by igneous processes is well organized and clearly written, whereas the chapter on metamorphic processes can only be described as excoriable. This is the fourth edition of a book that was first published in 1966, and, considering that the text deals with such long-dead issues as stress and antistress minerals, it seems to this reviewer that the chapter on metamorphic processes has not been updated since that date.

Frost, B. Ronald

61

Catalog of Mount St. Helens 2004 - 2005 Tephra Samples with Major- and Trace-Element Geochemistry  

USGS Publications Warehouse

This open-file report presents a catalog of information about 135 ash samples along with geochemical analyses of bulk ash, glass and individual mineral grains from tephra deposited as a result of volcanic activity at Mount St. Helens, Washington, from October 1, 2004 until August 15, 2005. This data, in conjunction with that in a companion report on 2004?2007 Mount St. Helens dome samples by Thornber and others (2008a) are presented in support of the contents of the U.S. Geological Survey Professional Paper 1750 (Sherrod and others, ed., 2008). Readers are referred to appropriate chapters in USGS Professional Paper 1750 for detailed narratives of eruptive activity during this time period and for interpretations of sample characteristics and geochemical data presented here. All ash samples reported herein are currently archived at the David A. Johnston Cascades Volcano Observatory in Vancouver, Washington. The Mount St. Helens 2004?2005 Tephra Sample Catalogue along with bulk, glass and mineral geochemistry are tabulated in 6 worksheets of the accompanying Microsoft Excel file, of2008-1131.xls. Samples in all tables are organized by collection date. Table 1 is a detailed catalog of sample information for tephra deposited downwind of Mount St. Helens between October 1, 2004 and August 18, 2005. Table 2 provides major- and trace-element analyses of 8 bulk tephra samples collected throughout that interval. Major-element compositions of 82 groundmass glass fragments, 420 feldspar grains, and 213 mafic (clinopyroxene, amphibole, hypersthene, and olivine) mineral grains from 12 ash samples collected between October 1, 2004 and March 8, 2005 are presented in tables 3 through 5. In addition, trace-element abundances of 198 feldspars from 11 ash samples (same samples as major-element analyses) are provided in table 6. Additional mineral and bulk ash analyses from 2004 and 2005 ash samples are published in chapters 30 (oxide thermometry; Pallister and others, 2008), 32 (amphibole major elements; Thornber and others, 2008b) and 37 (210Pb; 210Pb/226Pa; Reagan and others, 2008) of U.S. Geological Survey Professional Paper 1750 (Sherrod and others, 2008). A brief overview of sample collection methods is given below as an aid to deciphering the tephra sample catalog. This is followed by an explanation of the categories of sample information (column headers) in table 1. A summary of the analytical methods used to obtain the geochemical data in this report introduces the presentation of major- and trace-element geochemistry of Mount St. Helens 2004?2005 tephra samples in tables 2?6. Rhyolite glass standard analyses are reported (Appendix 1) to demonstrate the accuracy and precision of similar glass analyses presented herein.

Rowe, Michael C.; Thornber, Carl R.; Gooding, Daniel J.; Pallister, John S.

2008-01-01

62

Petrography, mineralogy, and trace element geochemistry of lunar meteorite Dhofar 1180  

NASA Astrophysics Data System (ADS)

Here we report the petrography, mineralogy, and trace element geochemistry of the Dhofar 1180 lunar meteorite. Dhofar 1180 is predominantly composed of fine-grained matrix with abundant mineral fragments and a few lithic and glassy clasts. Lithic clasts show a variety of textures including cataclastic, gabbroic, granulitic, ophitic/subophitic, and microporphyritic. Both feldspathic and mafic lithic clasts are present. Most feldspathic lithic clasts have a strong affinity to ferroan anorthositic suite rocks and one to magnesian suite rocks. Mafic lithic clasts are moderately to extremely Fe-rich. The Ti/[Ti+Cr]-Fe/[Fe+Mg] compositional trend of pyroxenes in mafic lithic clasts is consistent with that of low-Ti mare basalts. Glasses display a wide chemical variation from mafic to feldspathic. Some glasses are very similar to those from Apollo 16 soils. KREEP components are essentially absent in Dhofar 1180. One glassy clast is rich in K, REE and P, but its Mg/[Mg+Fe] is very low (0.25). It is probably a last-stage differentiation product of mare basalt. Molar Fe/Mn ratios of both olivine and pyroxene are essentially consistent with a lunar origin. Dhofar 1180 has a LREE-enriched (La 18 × CI, Sm 14 × CI) pattern with a small positive Eu anomaly (Eu 15 × CI). Th concentration is 0.7 ppm in Dhofar 1180. Petrography, mineralogy, and trace element geochemistry of Dhofar 1180 are different from those of other lunar meteorites, indicating that Dhofar 1180 represents a unique mingled lunar breccia derived from an area on the lunar nearside but far away from the center of the Imbrium Basin.

Zhang, A.; Hsu, W.

2009-10-01

63

Rare Earth Elements in Global Aqueous Media  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

64

Paragneiss zircon geochronology and trace element geochemistry, North Qaidam HP/UHP terrane, western China  

USGS Publications Warehouse

In the southeastern part of the North Qaidam terrane, near Dulan, paragneiss hosts minor peridotite and UHP eclogite. Zircon geochronology and trace element geochemistry of three paragneiss samples (located within a ???3 km transect) indicates that eclogite-facies metamorphism resulted in variable degrees of zircon growth and recrystallization in the three samples. Inherited zircon core age groups at 1.8 and 2.5 Ga suggest that the protoliths of these rocks may have received sediments from the Yangtze or North China cratons. Mineral inclusions, depletion in HREE, and absence of negative Eu anomalies indicate that zircon U-Pb ages of 431 ?? 5 Ma and 426 ?? 4 Ma reflect eclogite-facies zircon growth in two of the samples. Ti-in-zircon thermometry results are tightly grouped at ???660 and ???600 ??C, respectively. Inclusions of metamorphic minerals, scarcity of inherited cores, and lack of isotopic or trace element inheritance demonstrate that significant new metamorphic zircon growth must have occurred. In contrast, zircon in the third sample is dominated by inherited grains, and rims show isotopic and trace element inheritance, suggesting solid-state recrystallization of detrital zircon with only minor new growth. ?? 2009 Elsevier Ltd.

Mattinson, C.G.; Wooden, J.L.; Zhang, J.X.; Bird, D.K.

2009-01-01

65

Geochemistry of trace elements in coals from the Zhuji Mine, Huainan Coalfield, Anhui, China  

USGS Publications Warehouse

The abundances of nine major elements and thirty-eight trace elements in 520 samples of low sulfur coals from the Zhuji Mine, Huainan Coalfield, Anhui, China, were determined. Samples were mainly collected from 10 minable coal seams of 29 boreholes during exploration. The B content in coals shows that the influence of brackish water decreased toward the top of coal seams; marine transgression and regression occurred frequently in the Lower Shihezi Formation. A wide range of elemental abundances is found. Weighted means of Na, K, Fe, P, Be, B, Co, Ni, Cr, Se, Sb, Ba, and Bi abundances in Zhuji coals are higher, and the remainder elements are either lower or equal to the average values of elements in coals of northern China. Compared to the Chinese coals, the Zhuji coals are higher in Na, K, Be, B, Cr, Co, Se, Sn, Sb, and Bi, but lower in Ti, P, Li, V and Zn. The Zhuji coals are lower only in S, P, V and Zn than average U.S. and world coals. Potassium, Mg, Ca, Mn, Sr, As, Se, Sb and light rare earth elements (LREE) had a tendency to be enriched in thicker coal seams, whereas Fe, Ti, P, V, Co, Ni, Y, Mo, Pb and heavy rare earth elements (HREE) were inclined to concentrate in thinner coal seams. The enrichment of some elements in the Shanxi or Upper Shihezi Formations is related to their depositional environments. The elements are classified into three groups based on their stratigraphic distributions from coal seams 3 to 11-2, and the characteristics of each group are discussed. Lateral distributions of selected elements are also investigated. The correlation coefficients of elemental abundances with ash content show that the elements may be classified into four groups related to modes of occurrence of these elements. ?? 2009 Elsevier B.V. All rights reserved.

Sun, R.; Liu, G.; Zheng, L.; Chou, C.-L.

2010-01-01

66

Trace and minor element geochemistry of the rhyolitic volcanic rocks, Central North Island, New Zealand  

Microsoft Academic Search

Analytical data are presented for the following elements: Cs, Rb, Ba, K, Sr, Ca, Na, Fe, Mg, Cu, Co, Ni, Li, Sc, V, Cr, Ga, Al, Si, La, Y, and Zr. Eight samples were analysed by the spark source method for rare earths, Tl, Pb, Hf, Sn, Nb, Mo, Bi, and In. In addition to data on rhyolitic volcanics, a

A. Ewart; S. R. Taylor; Annette C. Capp

1968-01-01

67

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

68

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

E-print Network

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

van Westrenen, Wim

69

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

70

Earth, Air, Fire and Water in Our Elements  

ERIC Educational Resources Information Center

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

Lievesley, Tara

2007-01-01

71

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

PubMed

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

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

2014-04-01

72

Volcanism in the Sumisu Rift, I. Major element, volatile, and stable isotope geochemistry  

USGS Publications Warehouse

A bimodal volcanic suite with KAr ages of 0.05-1.40 Ma was collected from the Sumisu Rift using alvin. These rocks are contemporaneous with island arc tholeiite lavas of the Izu-Ogasawara arc 20 km to the east, and provide a present day example of volcanism associated with arc rifting and back-arc basin initiation. Major element geochemistry of the basalts is most similar to that of basalts found in other, more mature back-arc basins, which indicates that back-arc basins need not begin their magmatic evolution with lavas bearing strong arc signatures. Volatile concentrations distinguish Sumisu Rift basalts from island arc basalts and MORB. H2O contents, which are at least four times greater than in MORB, suppress plagioclase crystallization. This suppression results in a more mafic fractionating assemblage, which prevents Al2O3 depletion and delays the initiation of Fe2O3(tot) and TiO2 enrichment. However, unlike arc basalts, Fe3+ ??Fe ratios are only slightly higher than in MORB and are insufficient to cause magnetite saturation early enough to suppress Fe2O3(tot) and TiO2 enrichment. Thus, major element trends are more similar to those of MORB than arcs. H2O, CO2 and S are undersaturated relative to pure phase solubility curves, indicating exsolution of an H2O-rich mixed gas phase. High H2O S, high ??D, and low (MORB-like) ??34S ratios are considered primary and distinctive of the back-arc basin setting. ?? 1990.

Hochstaedter, A.G.; Gill, J.B.; Kusakabe, M.; Newman, S.; Pringle, M.; Taylor, B.; Fryer, P.

1990-01-01

73

Rare earth element association with foraminifera  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

74

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

USGS Publications Warehouse

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

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

1957-01-01

75

Elemental mixing systematics and Sr Nd isotope geochemistry of mélange formation: Obstacles to identification of fluid sources to arc volcanics  

NASA Astrophysics Data System (ADS)

We present major and trace element concentrations in conjunction with Sr-Nd isotope ratios to investigate the geochemical characteristics of mélange formation along the subduction zone slab-mantle interface. Mélange matrix of the Catalina Schist formed within an active subduction zone of the southern California borderland in Cretaceous time. Mélange formed through the synergistic effects of deformation and metasomatic fluid flow affecting peridotite, basaltic, and sedimentary protoliths to form hybridized bulk compositions not typical of seafloor "input" lithologies. In general, all elemental concentrations primarily reflect mechanical mixing processes, while fluid flow mediates all elemental systematics to a varying extent that is largely a function of inferred "mobility" for a particular element or the stability of suitable mineral hosts. Elemental data reveal that mineral stabilities defined by the evolution of bulk composition within mélange zones are probably the most important control of solid, liquid, or fluid geochemistry within the subduction system. Sr-Nd isotope ratios are highly variable and reflect contributions of mélange protoliths to varying extents. A weak mechanical mixing array present in Sr isotope data is strongly overprinted by a fluid signal that dominates mélange Sr systematics. Nd isotope data suggest that Nd is more conservative during metamorphism and is largely controlled by mechanical mixing. We argue that mélange formation is an intrinsic process to all subduction zones and that the geochemistry of mélange will impart the strongest control on the geochemistry of metasomatic agents (hydrous fluids, silicate melts, or miscible supercritical liquids) progressing to arc magmatic source regions in the mantle wedge. Mélange formation processes suggest that comparisons of subduction "inputs" to arc volcanic "outputs" as a means to infer recycling at subduction zones dangerously over-simplify the physics of the mass transfer in subduction zones, as subducted mass is consistently redistributed into novel bulk compositions. Such mélange zones along the slab-mantle interface simultaneously bear characteristic elemental or isotopic signals of several distinct input lithologies, while experiencing phase equilibria not typical of any input. We recommend that future studies explore the phase equilibria of hybridized systems and mineral trace element residency, as these processes provide for a physical baseline from which it will be possible to follow the path of subducted mass through the system.

King, Robert L.; Bebout, Gray E.; Moriguti, Takuya; Nakamura, Eizo

2006-06-01

76

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

77

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

USGS Publications Warehouse

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

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

1955-01-01

78

Trace element geochemistry of groundwater in a karst subterranean estuary (Yucatan Peninsula, Mexico)  

NASA Astrophysics Data System (ADS)

Trace element cycling within subterranean estuaries frequently alters the chemical signature of groundwater and may ultimately control the total chemical load to the coastal ocean associated with submarine groundwater discharge. Globally, karst landscapes occur over 12% of all coastlines. Subterranean estuaries in these regions are highly permeable, resulting in rapid infiltration of precipitation and transport of groundwater to the coast, and the predominant carbonate minerals are readily soluble. We studied the chemical cycling of barium (Ba), strontium (Sr), manganese (Mn), uranium (U), calcium (Ca) and radium (Ra) within the carbonate karst subterranean estuary of the Yucatan Peninsula, which is characterized by a terrestrial groundwater lens overlying marine groundwater intrusion with active submarine discharge through coastal springs. Terrestrial groundwater calcium (1-5 mmol kg-1) and alkalinity (3-8 mmol kg-1) are enriched over that predicted by equilibrium between recharging precipitation and calcite, which can be accounted for by groundwater organic matter respiration and subsequent dissolution of calcite, dolomite and gypsum. There is a close agreement between the observed terrestrial groundwater Sr/Ca, Mn/Ca, Ba/Ca and Ra/Ca and that predicted by equilibrium dissolution of calcite, thus the trace element content of terrestrial groundwater is largely determined by mineral dissolution. Subsequent mixing between terrestrial groundwater and the ocean within the actively discharging springs is characterized by conservative mixing of Sr, Mn, Ba and Ca, while U is variable and Ra displays a large enrichment (salinity: 1.9-34.9, Ba: 60-300 nmol kg-1, Sr: 15-110 ?mol kg-1, U: 0.3-35 nmol kg-1, Mn: 0.3-200 nmol kg-1, Ca: 4.3-12.9 mmol kg-1, 226Ra: 18-2140 dpm 100 L-1). The deep groundwater sampled through cenotes, local dissolution features, is typified by elevated Ba, Sr, Ca, Mn and Ra and the absence of U within marine groundwater, due to enhanced dissolution of the aquifer matrix following organic matter degradation and redox processes including sulfate reduction (salinity: 0.2-36.6, Ba: 7-1630 nmol kg-1, Sr: 1.3-210 ?mol kg-1, U: 0.3-18 nmol kg-1, Mn: 0.6-2600 nmol kg-1, Ca: 2.1-15.2 mmol kg-1, 226Ra 20-5120 dpm 100 L-1). However, there is no evidence in the spring geochemistry that deep marine groundwater within this reaction zone exchanges with the coastal ocean via spring discharge. Total submarine groundwater discharge rates calculated from radium tracers are 40-95 m3 m-1 d-1, with terrestrial discharge contributing 75 ± 25% of the total. Global estimates of chemical loading from karst subterranean estuaries suggest Sr and U fluxes are potentially 15-28% and 7-33% of total ocean inputs (8.2-15.3 mol y-1 and 4.0-7.7 mol y-1), respectively. Radium-226 inputs from karst subterranean estuaries are 34-50 times river inputs (6.7-9.9 × 1016 dpm y-1).

Gonneea, Meagan Eagle; Charette, Matthew A.; Liu, Qian; Herrera-Silveira, Jorge A.; Morales-Ojeda, Sara M.

2014-05-01

79

Anthropogenic influence on trace element geochemistry of healing mud (peloid) from Makirina Cove (Croatia)  

NASA Astrophysics Data System (ADS)

Due to their balneotherapeutic features, the organic-rich sediments in Makirina Cove are an important source of healing mud. An environmental geochemistry approach using normalization techniques was applied to evaluate the anthropogenic contribution of trace metals to sediments used as healing mud. Sediment geochemistry was found to be associated with land-use change and storm events, as well as with proximity of a road with heavy traffic in the summer months. Local valley topography preferentially channels lithogenic and pollutant transport to the cove. Concentrations and distribution of trace metals indicate lithogenic (Ni, Cr, Co) and anthropogenic (Pb, Cu, Zn and Se) contributions to the sediments. The calculation of enrichment factors indicates a moderate (EFs between 2-3.5) input of anthropogenic Cu and Pb in surficial sediments to a depth of 10 cm. Patients using the Makirina Cove sediments as healing mud could be to some extent exposed to enhanced uptake of metals from anthropogenic sources via dermal contact.

Miko, S.; Koch, G.; Mesi?, S.; Šparica-Miko, M.; Šparica, M.; ?epelak, R.; Ba?ani, A.; Vre?a, P.; Dolenec, T.; Bergant, S.

2008-08-01

80

Heterogeneous accretion and the moderately volatile element budget of Earth.  

PubMed

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

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

2010-05-14

81

Artificial Radioactivity of Dysprosium and other Rare Earth Elements  

Microsoft Academic Search

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

G. Hevesy; Hilde Levi

1935-01-01

82

doi:10.1016/S0016-7037(03)00161-3 Pb-Sr-He isotope and trace element geochemistry of the Cape Verde Archipelago  

E-print Network

doi:10.1016/S0016-7037(03)00161-3 Pb-Sr-He isotope and trace element geochemistry of the Cape Verde determined for basalts from the Cape Verde archipelago (Central Atlantic). Isotopic and chemical variations components in the source of the Cape Verde basalts: (1) recycled 1.6-Ga oceanic crust (high 206 Pb/204 Pb

Escrig, Stéphane

83

Distribution and geochemistry of selected trace elements in the Sacramento River near Keswick Reservoir  

USGS Publications Warehouse

The effect of heavy metals from the Iron Mountain Mines (IMM) Superfund site on the upper Sacramento River is examined using data from water and bed sediment samples collected during 1996-97. Relative to surrounding waters, aluminum, cadmium, cobalt, copper, iron, lead, manganese, thallium, zinc and the rare-earth elements (REE) were all present in high concentrations in effluent from Spring Creek Reservoir (SCR), which enters into the Sacramento River in the Spring Creek Arm of Keswick Reservoir. SCR was constructed in part to regulate the flow of acidic, metal-rich waters draining the IMM Superfund site. Although virtually all of these metals exist in SCR in the dissolved form, upon entering Keswick Reservoir they at least partially converted via precipitation and/or adsorption to the particulate phase. In spite of this, few of the metals settled out; instead the vast majority was transported colloidally down the Sacramento River at least to Bend Bridge, 67 km from Keswick Dam. The geochemical influence of IMM on the upper Sacramento River was variable, chiefly dependent on the flow of Spring Creek. Although the average flow of the Sacramento River at Keswick Dam is 250 m3/s (cubic meters per second), even flows as low as 0.3 m3/s from Spring Creek were sufficient to account for more than 15% of the metals loading at Bend Bridge, and these proportions increased with increasing Spring Creek flow. The dissolved proportion of the total bioavailable load was dependent on the element but steadily decreased for all metals, from near 100% in Spring Creek to values (for some elements) of less than 1% at Bend Bridge; failure to account for the suspended sediment load in assessments of the effect of metals transport in the Sacramento River can result in estimates which are low by as much as a factor of 100.

Antweiler, Ronald C.; Taylor, Howard E.; Alpers, Charles N.

2012-01-01

84

Trace-element geochemistry of metabasaltic rocks from the Yukon-Tanana Upland and implications for the origin of tectonic assemblages in east-central Alaska  

USGS Publications Warehouse

We present major- and trace- element geochemical data for 27 amphibolites and six greenstones from three structural packages in the Yukon-Tanana Upland of east-central Alaska: the Lake George assemblage (LG) of Devono-Mississippian augen gneiss, quartz-mica schist, quartzite, and amphibolite; the Taylor Mountain assemblage (TM) of mafic schist and gneiss, marble, quartzite, and metachert; and the Seventymile terrane of greenstone, serpentinized peridotite, and Mississippian to Late Triassic metasedimentary rocks. Most LG amphibolites have relatively high Nb, TiO2, Zr, and light rare earth element contents, indicative of an alkalic to tholeiitic, within-plate basalt origin. The within-plate affinities of the LG amphibolites suggest that their basaltic parent magmas developed in an extensional setting and support a correlation of these metamorphosed continental-margin rocks with less metamorphosed counterparts across the Tintina fault in the Selwyn Basin of the Canadian Cordillera. TM amphibolites have a tholeiitic or calc-alkalic composition, low normalized abundances of Nb and Ta relative to Th and La, and Ti/V values of <20, all indicative of a volcanic-arc origin. Limited results from Seventymile greenstones indicate a tholeiitic or calc-alkalic composition and intermediate to high Ti/V values (27-48), consistent with either a within-plate or an ocean-floor basalt origin. Y-La-Nb proportions in both TM and Seventymile metabasalts indicate the proximity of the arc and marginal basin to continental crust. The arc geochemistry of TM amphibolites is consistent with a model in which the TM assemblage includes arc rocks generated above a west-dipping subduction zone outboard of the North American continental margin in mid-Paleozoic through Triassic time. The ocean-floor or within-plate basalt geochemistry of the Seventymile greenstones supports the correlation of the Seventymile terrane with the Slide Mountain terrane in Canada and the hypothesis that these oceanic rocks originated in a basin between the continental margin and an arc to the west.

Dusel-Bacon, C.; Cooper, K.M.

1999-01-01

85

Spherical disharmonics in the Earth sciences and the spatial solution: Ridges, hotspots, slabs, geochemistry and tomography correlations  

NASA Technical Reports Server (NTRS)

There is increasing use of statistical correlations between geophysical fields and between geochemical and geophysical fields in attempts to understand how the Earth works. Typically, such correlations have been based on spherical harmonic expansions. The expression of functions on the sphere as spherical harmonic series has many pitfalls, especially if the data are nonuniformly and/or sparsely sampled. Many of the difficulties involved in the use of spherical harmonic expansion techniques can be avoided through the use of spatial domain correlations, but this introduces other complications, such as the choice of a sampling lattice. Additionally, many geophysical and geochemical fields fail to satisfy the assumptions of standard statistical significance tests. This is especially problematic when the data values to be correlated with a geophysical field were collected at sample locations which themselves correlate with that field. This paper examines many correlations which have been claimed in the past between geochemistry and mantle tomography and between hotspot, ridge, and slab locations and tomography using both spherical harmonic coefficient correlations and spatial domain correlations. No conclusively significant correlations are found between isotopic geochemistry and mantle tomography. The Crough and Jurdy (short) hotspot location list shows statistically significant correlation with lowermost mantle tomography for degree 2 of the spherical harmonic expansion, but there are no statistically significant correlations in the spatial case. The Vogt (long) hotspot location list does not correlate with tomography anywhere in the mantle using either technique. Both hotspot lists show a strong correlation between hotspot locations and geoid highs when spatially correlated, but no correlations are revealed by spherical harmonic techniques. Ridge locations do not show any statistically significant correlations with tomography, slab locations, or the geoid; the strongest correlation is with lowermost mantle tomography, which is probably spurious. The most striking correlations are between mantle tomography and post-Pangean subducted slabs. The integrated locations of slabs correlate strongly with fast areas near the transition zone and the core-mantle boundary and with slow regions from 1022-1248 km depth. This seems to be consistent with the 'avalanching' downwellings which have been indicated by models of the mantle which include an endothermic phase transition at the 670-km discontinuity, although this is not a unique interpretation. Taken as a whole, these results suggest that slabs and associated cold downwellings are the dominant feature of mantle convection. Hotspot locations are no better correlated with lower mantle tomography than are ridge locations.

Ray, Terrill W.; Anderson, Don L.

1994-01-01

86

Primitive magmas of the Earth and Moon : a petrologic investigation of magma genesis and evolution  

E-print Network

Field studies, major and trace element geochemistry, isotopes, petrography, phase equilibrium experiments and thermodynamics are used investigate and understand primitive melts from the Earth and the Moon. Chapter 1 ...

Barr, Jay Arthur

2010-01-01

87

Petrology and trace element geochemistry of Tissint, the newest shergottite fall  

NASA Astrophysics Data System (ADS)

AbstractThe fall and recovery of the Tissint meteorite in 2011 created a rare opportunity to examine a Martian sample with a known, short residence time on <span class="hlt">Earth</span>. Tissint is an olivine-phyric shergottite that accumulated olivine antecrysts within a single magmatic system. Coarse olivine grains with nearly homogeneous cores of Mg# >80 suggest slow re-equilibration. Many macroscopic features of this sample resemble those of LAR 06319, including the olivine crystal size distribution and the presence of evolved oxide and olivine compositions. Unlike LAR 06319, however, no magmatic hydrous phases were found in the analyzed samples of Tissint. Minor and trace <span class="hlt">element</span> compositions indicate that the meteorite is the product of closed-system crystallization from a parent melt derived from a depleted source, with no obvious addition of a LREE-rich (crustal?) component prior to or during crystallization. The whole-rock REE pattern is similar to that of intermediate olivine-phyric shergottite EETA 79001 lithology A, and could also be approximated by a more olivine-rich version of depleted basaltic shergottite QUE 94201. Magmatic oxygen fugacities are at the low end of the shergottite range, with log fO2 of QFM-3.5 to -4.0 estimated based on early-crystallized minerals and QFM-2.4 estimated based on the Eu in pyroxene oxybarometer. These values are similarly comparable to other depleted shergottites, including SaU 005 and QUE 94201. Tissint occupies a previously unsampled niche in shergottite chemistry: containing olivines with Mg# >80, resembling the enriched olivine-phyric shergottite LAR 06319 in its crystallization path, and comparable to intermediate olivine-phyric shergottite EETA 79001A, depleted olivine-phyric shergottite DaG 476, and depleted basaltic shergottite QUE 94201 in its trace <span class="hlt">element</span> abundances and oxygen fugacity. The apparent absence of evidence for terrestrial alteration in Tissint (particularly in trace <span class="hlt">element</span> abundances in the whole-rock and individual minerals) confirms that exposure to the arid desert environment results in only minimal weathering of samples, provided the exposure times are brief.</p> <div class="credits"> <p class="dwt_author">Balta, J. Brian; Sanborn, Matthew E.; Udry, Arya; Wadhwa, Meenakshi; McSween, Harry Y.</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">88</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014M%26PS..tmp..129B"> <span id="translatedtitle">Petrology and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of Tissint, the newest shergottite fall</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><abstract xml:id="maps12403-abs-0001" type="main"><title type="main">AbstractThe fall and recovery of the Tissint meteorite in 2011 created a rare opportunity to examine a Martian sample with a known, short residence time on <span class="hlt">Earth</span>. Tissint is an olivine-phyric shergottite that accumulated olivine antecrysts within a single magmatic system. Coarse olivine grains with nearly homogeneous cores of Mg# >80 suggest slow re-equilibration. Many macroscopic features of this sample resemble those of LAR 06319, including the olivine crystal size distribution and the presence of evolved oxide and olivine compositions. Unlike LAR 06319, however, no magmatic hydrous phases were found in the analyzed samples of Tissint. Minor and trace <span class="hlt">element</span> compositions indicate that the meteorite is the product of closed-system crystallization from a parent melt derived from a depleted source, with no obvious addition of a LREE-rich (crustal?) component prior to or during crystallization. The whole-rock REE pattern is similar to that of intermediate olivine-phyric shergottite EETA 79001 lithology A, and could also be approximated by a more olivine-rich version of depleted basaltic shergottite QUE 94201. Magmatic oxygen fugacities are at the low end of the shergottite range, with log fO2 of QFM-3.5 to -4.0 estimated based on early-crystallized minerals and QFM-2.4 estimated based on the Eu in pyroxene oxybarometer. These values are similarly comparable to other depleted shergottites, including SaU 005 and QUE 94201. Tissint occupies a previously unsampled niche in shergottite chemistry: containing olivines with Mg# >80, resembling the enriched olivine-phyric shergottite LAR 06319 in its crystallization path, and comparable to intermediate olivine-phyric shergottite EETA 79001A, depleted olivine-phyric shergottite DaG 476, and depleted basaltic shergottite QUE 94201 in its trace <span class="hlt">element</span> abundances and oxygen fugacity. The apparent absence of evidence for terrestrial alteration in Tissint (particularly in trace <span class="hlt">element</span> abundances in the whole-rock and individual minerals) confirms that exposure to the arid desert environment results in only minimal weathering of samples, provided the exposure times are brief.</p> <div class="credits"> <p class="dwt_author">Balta, J. Brian; Sanborn, Matthew E.; Udry, Arya; Wadhwa, Meenakshi; McSween, Harry Y.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">89</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70026818"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> partitioning between hydrous ferric oxides and acid mine water during iron oxidation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Ferrous iron rapidly oxidizes to Fe (III) and precipitates as hydrous Fe (III) oxides in acid mine waters. This study examines the effect of Fe precipitation on the rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) <span class="hlt">geochemistry</span> of acid mine waters to determine the pH range over which REEs behave conservatively and the range over which attenuation and fractionation occur. Two field studies were designed to investigate REE attenuation during Fe oxidation in acidic, alpine surface waters. To complement these field studies, a suite of six acid mine waters with a pH range from 1.6 to 6.1 were collected and allowed to oxidize in the laboratory at ambient conditions to determine the partitioning of REEs during Fe oxidation and precipitation. Results from field experiments document that even with substantial Fe oxidation, the REEs remain dissolved in acid, sulfate waters with pH below 5.1. Between pH 5.1 and 6.6 the REEs partitioned to the solid phases in the water column, and heavy REEs were preferentially removed compared to light REEs. Laboratory experiments corroborated field data with the most solid-phase partitioning occurring in the waters with the highest pH. ?? 2004 Elsevier Ltd. All rights reserved.</p> <div class="credits"> <p class="dwt_author">Verplanck, P.L.; Nordstrom, D.K.; Taylor, H.E.; Kimball, B.A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">90</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24628583"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> distributions and trends in natural waters with a focus on groundwater.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Systematically varying properties and reactivities have led to focused research of the environmental forensic capabilities of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE). Increasing anthropogenic inputs to natural systems may permanently alter the natural signatures of REE, motivating characterization of natural REE variability. We compiled and analyzed reported dissolved REE concentration data over a wide range of natural water types (ground-, ocean, river, and lake water) and groundwater chemistries (e.g., fresh, brine, and acidic) with the goal of quantifying the extent of natural REE variability, especially for groundwater systems. Quantitative challenges presented by censored data were addressed with nonparametric distributions and regressions. Reported measurements of REE in natural waters range over nearly 10 orders of magnitude, though the majority of measurements are within 2-4 orders of magnitude, and are highly correlated with one another. Few global correlations exist among dissolved abundance and bulk solution properties in groundwater, indicating the complex nature of source-sink terms and the need for care when comparing results between studies. This collection, homogenization, and analysis of a disparate literature facilitates interstudy comparison and provides insight into the wide range of variables that influence REE <span class="hlt">geochemistry</span>. PMID:24628583</p> <div class="credits"> <p class="dwt_author">Noack, Clinton W; Dzombak, David A; Karamalidis, Athanasios K</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-04-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">91</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5563033"> <span id="translatedtitle">Rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in hot brines (165 to 190 degree C) from the Salton Sea geothermal field</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Rare-<span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations are important indicators for revealing various chemical fractionation processes (water/rock interactions) and source region <span class="hlt">geochemistry</span>. Since the REE patterns are characteristic of geologic materials (basalt, granite, shale, sediments, etc.) and minerals (K-feldspar, calcite, illite, epidote, etc.), their study in geothermal fluids may serve as a geothermometer. The REE study may also enable us to address the issue of groundwater mixing. In addition, the behavior of the REE can serve as analogs of the actinides in radioactive waste (e.g., neodymium is an analog of americium and curium). In this paper, the authors port the REE data for a Salton Sea Geothermal Field (SSGF) brine (two aliquots: port 4 at 165{degree}C and port 5 at 190{degree}C) and six associated core samples.</p> <div class="credits"> <p class="dwt_author">Lepel, E.A.; Laul, J.C.; Smith, M.R.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">92</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24324274"> <span id="translatedtitle"><span class="hlt">Elemental</span> <span class="hlt">geochemistry</span> of sedimentary rocks at Yellowknife Bay, Gale crater, Mars.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The <span class="hlt">geochemistry</span> of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars. PMID:24324274</p> <div class="credits"> <p class="dwt_author">McLennan, S M; Anderson, R B; Bell, J F; Bridges, J C; Calef, F; Campbell, J L; Clark, B C; Clegg, S; Conrad, P; Cousin, A; Des Marais, D J; Dromart, G; Dyar, M D; Edgar, L A; Ehlmann, B L; Fabre, C; Forni, O; Gasnault, O; Gellert, R; Gordon, S; Grant, J A; Grotzinger, J P; Gupta, S; Herkenhoff, K E; Hurowitz, J A; King, P L; Le Mouélic, S; Leshin, L A; Léveillé, R; Lewis, K W; Mangold, N; Maurice, S; Ming, D W; Morris, R V; Nachon, M; Newsom, H E; Ollila, A M; Perrett, G M; Rice, M S; Schmidt, M E; Schwenzer, S P; Stack, K; Stolper, E M; Sumner, D Y; Treiman, A H; VanBommel, S; Vaniman, D T; Vasavada, A; Wiens, R C; Yingst, R A</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-24</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">93</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.yale.edu/denglab/paper/PNAS-2014-Wang-1413376111.pdf"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> activate endocytosis in plant cells Lihong Wanga,b,1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> activate endocytosis in plant cells Lihong Wanga,b,1 , Jigang Lic,d,1 , Qing (sent for review May 15, 2014) It has long been observed that rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) regulate, such as rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs), have been observed for a long time to be beneficial to plant growth (1, 2</p> <div class="credits"> <p class="dwt_author">Deng, Xing-Wang</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">94</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.wesleyan.edu/planetary/pubs/gammonsetal.pdf"> <span id="translatedtitle">Hydrogeochemistry and rare <span class="hlt">earth</span> <span class="hlt">element</span> behavior in a volcanically acidified watershed in Patagonia, Argentina</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">and analyzed for major ions, trace metals, and rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE). The concentrations of REE in the RioHydrogeochemistry and rare <span class="hlt">earth</span> <span class="hlt">element</span> behavior in a volcanically acidified watershed to oxidation of sulfide minerals. D 2005 Elsevier B.V. All rights reserved. Keywords: Rare <span class="hlt">earth</span> <span class="hlt">elements</span></p> <div class="credits"> <p class="dwt_author">Royer, Dana</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">95</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19890011981&hterms=Invertebrates&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DInvertebrates"> <span id="translatedtitle">Trace <span class="hlt">element</span> and isotope <span class="hlt">geochemistry</span> of Cretaceous-Tertiary boundary sediments: identification of extra-terrestrial and volcanic components</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Trace <span class="hlt">element</span> and stable isotope analyses were performed on a series of sediment samples crossing the Cretaceous-Tertiary (K-T) boundary from critical sections at Aumaya and Sopelano, Spain. The aim is to possibly distinguish extraterrestrial vs. volcanic or authigenic concentration of platinum group and other <span class="hlt">elements</span> in K-T boundary transitional sediments. These sediments also have been shown to contain evidence for step-wise extinction of several groups of marine invertebrates, associated with negative oxygen and carbon isotope excursions occurring during the last million years of the Cretaceous. These isotope excursions have been interpreted to indicate major changes in ocean thermal regime, circulation, and ecosystems that may be related to multiple events during latest Cretaceous time. Results to date on the petrographic and geochemical analyses of the Late Cretaceous and Early Paleocene sediments indicate that diagenesis has obviously affected the trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> and stable isotope compositions at Zumaya. Mineralogical and geochemical analysis of K-T boundary sediments at Zumaya suggest that a substantial fraction of anomalous trace <span class="hlt">elements</span> in the boundary marl are present in specific mineral phases. Platinum and nickel grains perhaps represent the first direct evidence of siderophile-rich minerals at the boundary. The presence of spinels and Ni-rich particles as inclusions in aluminosilicate spherules from Zumaya suggests an original, non-diagenetic origin for the spherules. Similar spherules from southern Spain (Caravaca), show a strong marine authigenic overprint. This research represents a new approach in trying to directly identify the sedimentary mineral components that are responsible for the trace <span class="hlt">element</span> concentrations associated with the K-T boundary.</p> <div class="credits"> <p class="dwt_author">Margolis, S. V.; Doehne, E. F.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">96</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3216626"> <span id="translatedtitle">Uncovering the Global Life Cycles of the Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) are a group of fifteen <span class="hlt">elements</span> 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 <span class="hlt">elements</span>. PMID:22355662</p> <div class="credits"> <p class="dwt_author">Du, Xiaoyue; Graedel, T. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">97</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012AGUFMGC53C1290S"> <span id="translatedtitle">Anthropogenic Disturbance of <span class="hlt">Element</span> Cycles at the <span class="hlt">Earth</span>'s Surface</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The extent to which humans are modifying <span class="hlt">Earth</span>'s surface chemistry can be quantified by comparing total anthropogenic <span class="hlt">element</span> fluxes with their natural counterparts [1]. We determine anthropogenic mass transfer of 77 <span class="hlt">elements</span> from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compared it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions and - for helium - hydrodynamic escape from the <span class="hlt">Earth</span>'s atmosphere. In addition, we introduce an approach to correct for losses during industrial processing of <span class="hlt">elements</span> belonging to geochemically coherent groups, and explicitly incorporated uncertainties of <span class="hlt">element</span> mass fluxes through Monte Carlo simulations [2]. Our assessment indicates that anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium are greater than the respective natural fluxes. For these <span class="hlt">elements</span> mining is the major factor of human dominance, whereas petroleum burning strongly influence the surficial cycle of rhenium. Apart from these 11 <span class="hlt">elements</span> there are 15 additional <span class="hlt">elements</span> whose anthropogenic fluxes may surpass their corresponding natural fluxes. Anthropogenic fluxes of the remaining <span class="hlt">elements</span> are smaller than their corresponding natural fluxes although a significant human influence is observed for all of them. For example, ~20% of the annual fluxes of C, N, and P can be attributed to human activities. Such disturbances, though small compared with natural fluxes, can significantly alter concentrations in near-surface reservoirs and affect ecosystems if they are sustained over time scales similar to or longer than the residence time of <span class="hlt">elements</span> in the respective reservoir. Examples are the continuing input of CO2 to the atmosphere that has led to a 40% increase in atmospheric CO2 concentrations, and the atmospheric redistribution of reactive nitrogen and accumulation in remote ecosystems. We note that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 <span class="hlt">elements</span> may surpass their corresponding natural fluxes. [1] Klee and Graedel (2004), Annu. Rev. Environ. Resour., 29, p. 69-107 [2] Sen and Peucker-Ehrenbrink (2012), Environ. Sci. Technol., dx.doi.org/10.1021/es301261x</p> <div class="credits"> <p class="dwt_author">Sen, I. S.; Peucker-Ehrenbrink, B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">98</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41973485"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of Muong-Nong type tektites. IV - Selected trace <span class="hlt">element</span> correlations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Muong-Nong type tektites are distinct from other tektites in their shape, size, petrographical characteristics, and chemistry. Volatile <span class="hlt">elements</span> are enriched, but other trace <span class="hlt">elements</span> do not show large differences when compared to normal splash-form tektites. An analysis is made of nineteen Muong-Nong type tektites for 40-50 <span class="hlt">elements</span>. Fifteen nonvolatile <span class="hlt">elements</span> are discussed in this paper. It is shown that the</p> <div class="credits"> <p class="dwt_author">C. Koeberl; F. Kluger; W. Keisl</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">99</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19910053953&hterms=zircon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dzircon"> <span id="translatedtitle">Compositional and phase relations among rare <span class="hlt">earth</span> <span class="hlt">element</span> minerals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">A review is presented that mainly treats minerals in which the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> are essential constituents, e.g., bastnaesite, monazite, xenotime, aeschynite, allanite. The chemical mechanisms and limits of REE substitution in some rock-forming minerals (zircon, apatite, titanite, garnet) are also derived. Vector representation of complex coupled substitutions in selected REE-bearing minerals is examined and some comments on REE-partitioning between minerals as related to acid-based tendencies and mineral stabilities are presented. As the same or analogous coupled substitutions involving the REE occur in a wide variety of mineral structures, they are discussed together.</p> <div class="credits"> <p class="dwt_author">Burt, D. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">100</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5216629"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> patterns in biotite, muscovite and tourmaline minerals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> 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.</p> <div class="credits"> <p class="dwt_author">Laul, J.C.; Lepel, E.A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-04-21</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_4");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a 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showDiv("page_7");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">101</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.H34C..02N"> <span id="translatedtitle">Source and mobility of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> in a sedimentary aquifer system: Aquitaine basin (Southern France)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The study of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in natural waters initially involved an examination of their occurrence and behavior in seawater and coastal waters such as estuaries. Since the 1990s, REE <span class="hlt">geochemistry</span> has been applied to continental waters such as rivers and lakes and groundwaters. Rare <span class="hlt">earth</span> <span class="hlt">elements</span>) are of great interest because of their unique characteristics and have been used in the study of many geological processes like weathering and water-rock interaction processes, provenance of sediments, etc... With the evolution of analytical techniques like new generation ICP-MS, much attention had been paid towards the water <span class="hlt">geochemistry</span> of REEs. However, there is a need of more investigations devoted to REEs in large groundwater systems, especially on the understanding of the distribution of REEs and their evolution in such systems. In this frame, large sedimentary aquifer systems often constitute strategic water resources for drinking water supply, agriculture irrigation and industry, but can also represent an energetic resource for geothermal power. Large water abstractions can induce complete modification of the natural functioning of such aquifer systems. These large aquifer systems thus require water management at the basin scale in order to preserve both water quantity and quality. The large Eocene Sand aquifer system of the Aquitaine sedimentary basin was studied through various hydrological, chemical and isotopic tools. This system extends over 116,000 km2 in the South west part of the French territory. The aquifer being artesian in the west of the district and confined with piezometric levels around 250-m depth in the east. The 'Eocene Sands', composed of sandy Tertiary sediments alternating with carbonate deposits, is a multi-layer system with high permeability and a thickness of several tens of metres to a hundred metres. The Eocene Sand aquifer system comprises at least five aquifers: Paleocene, Eocene infra-molassic sands (IMS), early Eocene, middle Eocene, and late Eocene. One important feature, in these confined systems isolated from anthropogenic influence, is the range in salinities by a factor of 10, from 250 mg/L up to 2.5 g/L. The ?REE, in the range 2-54 ng/L, with a dependence on salinity when expressed in % HCO3 or SO4, reflect the carbonate or evaporite source of REEs. The UCC normalized-REE patterns show a large variability as exemplified by the REE flat patterns-low SREE associated with salinity controlled by HCO3. In the present work, the REEs are investigated in terms of saturation indices, speciation modelling, REE patterns in order to recognize the aquifer type hosting groundwater and decipher the origin of the salinity of the groundwater as some part of the aquifer display in the groundwater concentration of chemical <span class="hlt">element</span> exceeding the drinking water standard (SO4, F...). Such high concentrations of naturally-occurring substances (e.g. unaffected by human activities) can have negative impacts on groundwater thresholds and deciphering their origin by means of geochemical tools like REE is a remaining challenge.</p> <div class="credits"> <p class="dwt_author">Negrel, P. J.; Petelet-Giraud, E.; Millot, R.; Malcuit, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">102</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014ChPhB..23e7403J"> <span id="translatedtitle">Magnetic property improvement of niobium doped with rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium. Rare <span class="hlt">earth</span> <span class="hlt">elements</span> like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping <span class="hlt">elements</span> and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.</p> <div class="credits"> <p class="dwt_author">Jiang, Tao; He, Fei-Si; Jiao, Fei; He, Fa; Lu, Xiang-Yang; Zhao, Kui; Zhao, Hong-Yun; You, Yu-Song; Chen, Lin</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">103</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geol.umd.edu/"> <span id="translatedtitle">University of Maryland: <span class="hlt">Geochemistry</span> Laboratories</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This extensive website features the University of Maryland's <span class="hlt">Geochemistry</span> Laboratories' efforts to "produce the highest quality <span class="hlt">elemental</span> and isotopic data, to teach students and visitors the techniques involved with gathering such data," and to develop new methods and instrumentation in the field of <span class="hlt">elemental</span> and isotope measurements." Users can discover the Thermal Ionization, Plasma, and Gas Source laboratories; as well as the Chemical Processing Lab and the Mineral Separation and Rock Preparation Laboratories. Through the links to the staff members and three of the laboratories, researchers can learn about the department's studies of the <span class="hlt">Earth</span>'s core, mantle, and crust; the atmosphere and hydrosphere; and the isotopic evolution of the solar system. Throughout the website, students and educators can find educational materials on topics including ablation spot characteristics and environmental safety.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">104</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3906100"> <span id="translatedtitle">Trace <span class="hlt">Elemental</span> Imaging of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> Discriminates Tissues at Microscale in Flat Fossils</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting <span class="hlt">elemental</span> distributions greatly improved the discrimination of skeletal <span class="hlt">elements</span> material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline <span class="hlt">earth</span> <span class="hlt">elements</span> and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare <span class="hlt">earth</span> <span class="hlt">elements</span>. Local quantification of rare <span class="hlt">earths</span> may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809</p> <div class="credits"> <p class="dwt_author">Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B.; Cohen, Serge X.; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">105</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24489809"> <span id="translatedtitle">Trace <span class="hlt">elemental</span> imaging of rare <span class="hlt">earth</span> <span class="hlt">elements</span> discriminates tissues at microscale in flat fossils.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting <span class="hlt">elemental</span> distributions greatly improved the discrimination of skeletal <span class="hlt">elements</span> material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline <span class="hlt">earth</span> <span class="hlt">elements</span> and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare <span class="hlt">earth</span> <span class="hlt">elements</span>. Local quantification of rare <span class="hlt">earths</span> may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809</p> <div class="credits"> <p class="dwt_author">Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B; Cohen, Serge X; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">106</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70034362"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of environmentally sensitive trace <span class="hlt">elements</span> in Permian coals from the Huainan coalfield, Anhui, China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">To study the geochemical characteristics of 11 environmentally sensitive trace <span class="hlt">elements</span> in the coals of the Permian Period from the Huainan coalfield, Anhui province, China, borehole samples of 336 coals, two partings, and four roof and floor mudstones were collected from mineable coal seams. Major <span class="hlt">elements</span> and selected trace <span class="hlt">elements</span> were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and hydride generation atomic absorption spectrometry (HAAS). The depositional environment, abundances, distribution, and modes of occurrence of trace <span class="hlt">elements</span> were investigated. Results show that clay and carbonate minerals are the principal inorganic constituents in the coals. A lower deltaic plain, where fluvial channel systems developed successively, was the likely depositional environment of the Permian coals in the Huainan coalfield. All major <span class="hlt">elements</span> have wider variation ranges than those of Chinese coals except for Mg and Fe. The contents of Cr, Co, Ni, and Se are higher than their averages for Chinese coals and world coals. Vertical variations of trace <span class="hlt">elements</span> in different formations are not significant except for B and Ba. Certain roof and partings are distinctly higher in trace <span class="hlt">elements</span> than underlying coal bench samples. The modes of occurrence of trace <span class="hlt">elements</span> vary in different coal seams as a result of different coal-forming environments. Vanadium, Cr, and Th are associated with aluminosilicate minerals, Ba with carbonate minerals, and Cu, Zn, As, Se, and Pb mainly with sulfide minerals. ?? 2011 Elsevier B.V.</p> <div class="credits"> <p class="dwt_author">Chen, J.; Liu, G.; Jiang, M.; Chou, C.-L.; Li, H.; Wu, B.; Zheng, L.; Jiang, D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">107</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014Litho.205..322K"> <span id="translatedtitle">Platinum-group <span class="hlt">element</span> (PGE) <span class="hlt">geochemistry</span> of Mesoarchean ultramafic-mafic cumulate rocks and chromitites from the Nuasahi Massif, Singhbhum Craton (India)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Mesoarchean Nuasahi Massif in eastern India comprises a lower ultramafic and an upper gabbro unit. The lower unit consists of orthopyroxenite, harzburgite, dunite and three chromitite bands. All of these rocks are characterized by adcumulate textures. The upper unit consists of gabbro with magnetite layers. At the contact between the eastern orthopyroxenite and the lower part of the upper gabbro, a sulfide-rich breccia zone with platinum-group-<span class="hlt">element</span> (PGE) mineralization is present. Detailed studies of major-, trace- and PGE abundances suggest that the ultramafic-mafic cumulate rocks, chromitites and breccias are genetically linked. The chondrite-normalized U-shaped rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) patterns of the harzburgite resemble those of Phanerozoic boninite. The overall U-shaped REE patterns of the ultramafic rocks indicate derivation of the parental magma from a metasomatized depleted mantle source. The upper gabbros have higher relative abundances of trace <span class="hlt">elements</span> than the lower ultramafic rocks, due to crystallization from a fractionated magma. Whole-rock <span class="hlt">geochemistry</span> suggests that the lower ultramafic cumulate rocks with chromitites crystallized from a boninitic parental magma, whereas the upper gabbros with magnetite bands may be formed from residual boninitic magma that was contaminated by more tholeiitic-like magmas. The boninitic parental magma that crystallized to form the lower ultramafic unit was most likely generated by second-stage melting of a depleted metasomatized mantle source in a supra-subduction zone (SSZ) setting and emplaced into crustal sequences. The PGE abundances in the Nuasahi rocks provide additional constraints on their geochemical evolution during the Mesoarchean. Primitive-mantle-normalized PGE diagrams show (1) Ru enrichment in chromitites (Pd/Ru = 0.17-0.64), (2) Pd/Pt fractionation in both chromitites (Pd/Pt = 3.1) and ultramafic rocks (Pd/Pt = 0.62), (3) marked Ir depletion in ultramafic rocks (Pd/Ir = 6.3) and (4) overall PGE enrichment in chromitites (PGEtotal = 142-502 ppb). The large Ir depletion in the ultramafic rocks, and the overall Ir-depleted character of other rocks from the Nuasahi Massif, may be related to multiple episodes of melt extraction from the mantle source, giving it a subchondritic character.</p> <div class="credits"> <p class="dwt_author">Khatun, Sarifa; Mondal, Sisir K.; Zhou, Mei-Fu; Balaram, Vysetti; Prichard, Hazel M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">108</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.nrel.gov/docs/fy12osti/52659.pdf"> <span id="translatedtitle">NREL Highlights SCIENCE These polycrystalline cells use <span class="hlt">Earth</span>-abundant <span class="hlt">elements</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">NREL Highlights SCIENCE These polycrystalline cells use <span class="hlt">Earth</span>-abundant <span class="hlt">elements</span>. NREL scientists (CZTSe) solar cells, which are based on non-toxic, <span class="hlt">Earth</span>-abundant <span class="hlt">elements</span>. Recently, NREL demonstrated. Potential Impact CZTSe cells use <span class="hlt">Earth</span>-abundant materials that provide environmental benefits (non</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">109</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19840011975&hterms=Belief+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DBelief%2Bchange"> <span id="translatedtitle">The <span class="hlt">elements</span> of the <span class="hlt">Earth</span>'s magnetism and their secular changes between 1550 and 1915</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The results of an investigation about the magnetic agents outside the <span class="hlt">Earth</span>'s surface as well as the <span class="hlt">Earth</span>'s magnetic <span class="hlt">elements</span> for the epochs 1550, 1900, 1915 are presented. The secular changes of the <span class="hlt">Earth</span>'s magnetic <span class="hlt">elements</span> during the time interval 1550 - 1900 are also included.</p> <div class="credits"> <p class="dwt_author">Fritsche, H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">110</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geos.ed.ac.uk/homes/sklemme/publications/PK_GCA_2006.pdf"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> partitioning between titanite and silicate melts: Henry's law revisited</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> partitioning between titanite and silicate melts: Henry's law revisited Stefan <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) between titanite and a range of different silicate melts. Our results show that Henry's law of trace <span class="hlt">element</span> partitioning depends on bulk composition, the available partners</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">111</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25114214"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> activate endocytosis in plant cells.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">It has long been observed that rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) regulate multiple facets of plant growth and development. However, the underlying mechanisms remain largely unclear. Here, using electron microscopic autoradiography, we show the life cycle of a light REE (lanthanum) and a heavy REE (terbium) in horseradish leaf cells. Our data indicate that REEs were first anchored on the plasma membrane in the form of nanoscale particles, and then entered the cells by endocytosis. Consistently, REEs activated endocytosis in plant cells, which may be the cellular basis of REE actions in plants. Moreover, we discovered that a portion of REEs was successively released into the cytoplasm, self-assembled to form nanoscale clusters, and finally deposited in horseradish leaf cells. Taken together, our data reveal the life cycle of REEs and their cellular behaviors in plant cells, which shed light on the cellular mechanisms of REE actions in living organisms. PMID:25114214</p> <div class="credits"> <p class="dwt_author">Wang, Lihong; Li, Jigang; Zhou, Qing; Yang, Guangmei; Ding, Xiao Lan; Li, Xiaodong; Cai, Chen Xin; Zhang, Zhao; Wei, Hai Yan; Lu, Tian Hong; Deng, Xing Wang; Huang, Xiao Hua</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">112</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5984587"> <span id="translatedtitle">Pb-Sr-He isotope and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the Cape Verde Archipelago</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">New lead, strontium and helium isotopic data, together with trace <span class="hlt">element</span> concentrations, have been determined for basalts from the Cape Verde archipelago (Central Atlantic). Isotopic and chemical variations are observed at the scale of the archipelago and lead to the definition of two distinct groupings, in keeping with earlier studies. The Northern Islands (Santo Antão, São Vicente, São Nicolau and</p> <div class="credits"> <p class="dwt_author">Régis Doucelance; S T ´ EPHANE ESCRIG; Manuel Moreira; Clément Gariépy; Mark D. Kurz</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">113</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://web.mit.edu/tlgrove/www/pubs/pubs/110.pdf"> <span id="translatedtitle">Diffusive fractionation of trace <span class="hlt">elements</span> during production and transport of melt in <span class="hlt">Earth’s</span> upper mantle</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We have developed a numerical model to investigate the importance of diffusive chemical fractionation during production and transport of melt in <span class="hlt">Earth’s</span> upper mantle. The model incorporates new experimental data on the diffusion rates of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) in high-Ca pyroxene [Van Orman et al., Contrib. Mineral. Petrol. 141 (2001) 687–703] and pyrope garnet [Van Orman et al., Contrib.</p> <div class="credits"> <p class="dwt_author">James A. Van Orman; Timothy L. Grove; Nobumichi Shimizu</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">114</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014cosp...40E.102A"> <span id="translatedtitle"><span class="hlt">Elemental</span> processes of transport and energy conversion in <span class="hlt">Earth</span>'s magnetosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In the last 5 years observations from several missions and ground based observatories have honed in on the most <span class="hlt">elemental</span> aspects of flux transport and energy conversion. Dipolarization fronts and their counterpart in the distant magnetotail "anti-dipolarization" fronts, which together are refered to herein as "reconnection fronts", usher the recently reconnected flux tubes from the near-<span class="hlt">Earth</span> X-points and in the process convert magnetic energy to particle energy and wave radiation. On the tailward side they are responsible for plasmoid formation and acceleration. On the earthward side they result in <span class="hlt">elemental</span> substorm current wedges or wedglets, which were initially postulated from ground observations alone. Recent observations have revealed how the interaction of wedgelets and the inner magnetosphere takes place. Questions remain with regards to the physics of the energy transfer process from global magnetic energy to local heating and waves, and with regards to the initiation of the X-point activations in space. Observations indicate that the latter may be induced by polar cap or dayside activity, suggesting a direct link between dayside reconnection and nightside phenomena. The likely causal sequence of events and open questions in light of these recent observations, and the field's outlook in anticipation of upcoming coordinated observations from the international Heliophysics System Observatory will be discussed.</p> <div class="credits"> <p class="dwt_author">Angelopoulos, Vassilis</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">115</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20050210032&hterms=Sedimentology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSedimentology"> <span id="translatedtitle">Microbial Paleontology, Mineralogy and <span class="hlt">Geochemistry</span> of Modern and Ancient Thermal Spring Deposits and Their Recognition on the Early <span class="hlt">Earth</span> and Mars"</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The vision of this project was to improve our understanding of the processes by which microbiological information is captured and preserved in rapidly mineralizing sedimentary environments. Specifically, the research focused on the ways in which microbial mats and biofilms influence the sedimentology, <span class="hlt">geochemistry</span> and paleontology of modem hydrothermal spring deposits in Yellowstone national Park and their ancient analogs. Toward that goal, we sought to understand how the preservation of fossil biosignatures is affected by 1) taphonomy- the natural degradation processes that affect an organism from the time of its death, until its discovery as a fossil and 2) diagenesis- longer-term, post-depositional processes, including cementation and matrix recrystallization, which collectively affect the mineral matrix that contains fossil biosignature information. Early objectives of this project included the development of observational frameworks (facies models) and methods (highly-integrated, interdisciplinary approaches) that could be used to explore for hydrothermal deposits in ancient terranes on <span class="hlt">Earth</span>, and eventually on Mars.</p> <div class="credits"> <p class="dwt_author">Farmer, Jack D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">116</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006Litho..88....1C"> <span id="translatedtitle">Pb and rare <span class="hlt">earth</span> <span class="hlt">element</span> diffusion in xenotime</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Diffusion of Pb and the rare <span class="hlt">earth</span> <span class="hlt">elements</span> Sm, Dy and Yb have been characterized in synthetic xenotime under dry conditions. The synthetic xenotime was grown via a Na 2CO 3-MoO 3 flux method. The sources of diffusant for the rare <span class="hlt">earth</span> diffusion experiments were REE phosphate powders, with experiments run using sources containing a single REE. For Pb, the source consisted a mixture of YPO 4 and PbTiO 3. Experiments were performed by placing source and xenotime in Pt capsules, and annealing capsules in 1 atm furnaces for times ranging from 30 min to several weeks, at temperatures from 1000 to 1500 °C. The REE and Pb distributions in the xenotime were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relations are obtained for diffusion in xenotime, normal to (101): D=1.5×10exp?(-441±12 kJmol/R?T)ms.D=9.0×10exp?(-349±16 kJmol/R?T)ms.D=3.9×10exp?(-362±13 kJmol/R?T)ms. Diffusivities among the REE do not differ greatly in xenotime over the investigated temperature range, in contrast to findings for the REE in zircon [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare <span class="hlt">earth</span> diffusion in zircon. Chem. Geol. 134, 289-301.], where the LREE diffuse more slowly, and with higher activation energies for diffusion, than the heavier rare <span class="hlt">earths</span>. In zircon, these differences among diffusion of the rare <span class="hlt">earths</span> are attributed to the relatively large size of the REE with respect to Zr, for which they likely substitute in the zircon lattice. With the systematic increase in ionic radius from the heavy to lighter REE, this size mismatch becomes more pronounced and diffusivities of the LREE are as consequence slower. Although xenotime is isostructural with zircon, the REE are more closely matched in size to Y, so in xenotime this effect appears much smaller and the REE diffuse at similar rates. In addition, the process of diffusion in xenotime likely involves simple REE + 3 ? Y + 3 exchange, without charge compensation as needed for REE + 3 ? Zr + 4 exchange in zircon. This latter factor may also contribute to the large activation energies for diffusion of the REE in zircon (i.e., 691-841 kJ mol - 1 , [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare <span class="hlt">earth</span> diffusion in zircon. Chem. Geol. 134, 289-301.]), in comparison with those for xenotime. For Pb, the following Arrhenius relation is obtained (also normal to (101)): D=3.0×10exp?(-382±64 kJmol/R?T)ms. These measurements suggest that Pb diffusion in xenotime is quite slow, even slower than Pb diffusion in monazite and zircon, and considerably slower than diffusion of the REE in xenotime. Xenotime may therefore be even more retentive of Pb isotope signatures than either monazite or zircon in cases where Pb isotopes are altered solely by volume diffusion. However, because the activation energy for Pb diffusion in xenotime is lower than those for monazite and zircon, Pb diffusion may be somewhat faster at many temperatures of geologic interest in xenotime than in monazite or zircon.</p> <div class="credits"> <p class="dwt_author">Cherniak, D. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">117</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2000GPC....26..217S"> <span id="translatedtitle">Processes controlling trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of Arabian Sea sediments during the last 25,000 years</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Thirty seven deep-sea sediment cores from the Arabian Sea were studied geochemically (49 major and trace <span class="hlt">elements</span>) for four time slices during the Holocene and the last glacial, and in one high sedimentation rate core (century scale resolution) to detect tracers of past variations in the intensity of the atmospheric monsoon circulation and its hydrographic expression in the ocean surface. This geochemical multi-tracer approach, coupled with additional information on the grain size composition of the clastic fraction, the bulk carbonate and biogenic opal contents makes it possible to characterize the sedimentological regime in detail. Sediments characterized by a specific <span class="hlt">elemental</span> composition (enrichment) originated from the following sources: river suspensions from the Tapti and Narbada, draining the Indian Deccan traps (Ti, Sr); Indus sediments and dust from Rajasthan and Pakistan (Rb, Cs); dust from Iran and the Persian Gulf (Al, Cr); dust from central Arabia (Mg); dust from East Africa and the Red Sea (Zr/Hf, Ti/Al). C org, Cd, Zn, Ba, Pb, U, and the HREE are associated with the intensity of upwelling in the western Arabian Sea, but only those patterns that are consistently reproduced by all of these <span class="hlt">elements</span> can be directly linked with the intensity of the southwest monsoon. Relying on information from a single <span class="hlt">element</span> can be misleading, as each <span class="hlt">element</span> is affected by various other processes than upwelling intensity and nutrient content of surface water alone. The application of the geochemical multi-tracer approach indicates that the intensity of the southwest monsoon was low during the LGM, declined to a minimum from 15,000-13,000 14C year BP, intensified slightly at the end of this interval, was almost stable during the Bölling, Alleröd and the Younger Dryas, but then intensified in two abrupt successions at the end of the Younger Dryas (9900 14C year BP) and especially in a second event during the early Holocene (8800 14C year BP). Dust discharge by northwesterly winds from Arabia exhibited a similar evolution, but followed an opposite course: high during the LGM with two primary sources—the central Arabian desert and the dry Persian Gulf region. Dust discharge from both regions reached a pronounced maximum at 15,000-13,000 14C year. At the end of this interval, however, the dust plumes from the Persian Gulf area ceased dramatically, whereas dust discharge from central Arabia decreased only slightly. Dust discharge from East Africa and the Red Sea increased synchronously with the two major events of southwest monsoon intensification as recorded in the nutrient content of surface waters. In addition to the tracers of past dust flux and surface water nutrient content, the geochemical multi-tracer approach provides information on the history of deep sea ventilation (Mo, S), which was much lower during the last glacial maximum than during the Holocene. The multi-tracer approach—i.e. a few sedimentological parameters plus a set of geochemical tracers widely available from various multi-<span class="hlt">element</span> analysis techniques—is a highly applicable technique for studying the complex sedimentation patterns of an ocean basin, and, specifically in the case of the Arabian Sea, can even reveal the seasonal structure of climate change.</p> <div class="credits"> <p class="dwt_author">Sirocko, Frank; Garbe-Schönberg, Dieter; Devey, Colin</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">118</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/6579398"> <span id="translatedtitle">Trace-<span class="hlt">element</span> <span class="hlt">geochemistry</span> of gradient hole cuttings: Beowawe geothermal area, Nevada</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Multielement geochemical analysis of drill cuttings from 26 shallow temperature-gradient drill holes and of surface rock samples reveals trace <span class="hlt">element</span> distributions developed within these rocks as a consequence of chemical interaction with thermal fluid within the Beowawe geothermal area. The presently discharging thermal fluids are dilute in all components except silica, suggesting that the residence time of these fluids within the thermal reservoir has been short and that chemical interaction with the reservoir rock minimal. Interaction between these dilute fluids and rocks within the system has resulted in the development of weak chemical signatures. The absence of stronger signatures in rocks associated with the present system suggests that fluids have had a similar dilute chemistry for some time. The spatial distribution of <span class="hlt">elements</span> commonly associated with geothermal systems, such as As, Hg and Li, and neither laterally nor vertically continuous. This suggests that there is not now, nor has there been in the past, pervasive movement of thermal fluid throughout the sampled rock but, instead, that isolated chemical anomalies represent distinct fluid-flow chanels. Discontinuous As, Li and Hg concentrations near White Canyon to the east of the presently active surface features record the effects of chemical interaction of rocks with fluids chemically unlike the presently discharging fluids. The observed trace <span class="hlt">element</span> distributions suggest that historically the Beowawe area has been the center of more than one hydrothermal event and that the near-surface portion of the present hot-water geothermal system is controlled by a single source fracture, the Malpais Fault, or an intersection of faults at the sinter terrace.</p> <div class="credits"> <p class="dwt_author">Christensen, O.D.</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">119</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5224579"> <span id="translatedtitle">Stratigraphy and major <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the Lassen Volcanic Center, California</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Detailed geologic mapping of 200 km/sup 2/ in and near Lassen Volcanic National Park, California and reconnaissance of the surrounding area, combined with reinterpretation of data in the literature, allow definition of the Lassen Volcano Center and provide the stratigraphic framework necessary for interpretation of major-<span class="hlt">element</span> chemical data. The Lassen Volcanic Center developed in three stages. Stage I and II produced Brokeoff Volcanic, an andesitic composite cone that erupted mafic andesite to dacite 0.6 to 0.35 my ago. Volcanism then shifted in character and locale. Domes and flows of dacite and rhyodacite, and flows of hybrid andesite were erupted on the northern flank of Brokeoff Volcano during the period from 0.25 my ago to the present; these rocks comprise Stage III of the Lassen Volcanic Center. Rocks of the Lassen Volcanic Center are typical of subduction-related calc-alkaline volcanic rocks emplaced on a continental margin overlying sialic crust. Porphyritic andestic and dacite with high Al/sub 2/O/sub 3/, low TiO/sub 2/, medium K/sub 2/O, and FeO/MgO 1.5-2.0 are the most abundant rock types. Major-<span class="hlt">element</span> chemical trends of rock sequences indicate a mafic to silicic evolution for magmas of the Lassen Volcanic Center, probably owing to crystal fractionation of calc-alkaline basalt. 23 figs., 5 tabs.</p> <div class="credits"> <p class="dwt_author">Clynne, M.A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">120</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012GeCoA..83...79B"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of CI chondrites: Major and trace <span class="hlt">elements</span>, and Cu and Zn Isotopes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In order to check the heterogeneity of the CI chondrites and determine the average composition of this group of meteorites, we analyzed a series of six large chips (weighing between 0.6 and 1.2 g) of Orgueil prepared from five different stones. In addition, one sample from each of Ivuna and Alais was analyzed. Although the sizes of the chips used in this study were “large”, our results show evidence for minor chemical heterogeneity in Orgueil, particularly for alkali <span class="hlt">elements</span> and U. After removal of one outlier sample, the spread of the results is considerably reduced. For most of the 46 <span class="hlt">elements</span> analyzed in this study, the average composition calculated for Orgueil is in very good agreement with previous CI estimates. This average, obtained with a “large” mass of samples, is analytically homogeneous and is suitable for normalization purposes. Finally, the Cu and Zn isotopic ratios are homogeneously distributed within the CI parent body with a spread of less than 100 ppm per atomic mass unit (amu).</p> <div class="credits"> <p class="dwt_author">Barrat, J. A.; Zanda, B.; Moynier, F.; Bollinger, C.; Liorzou, C.; Bayon, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_5");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' 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href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_8");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">121</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21176850"> <span id="translatedtitle">Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of Jurassic coals from Eastern Black Sea Region, NE-Turkey</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The majority of coal deposits in the world are of Carboniferous and Tertiary age but Jurassic coals are seldom present. They are also exposed in northern Turkey and occur both at the lower and upper sections of the Liassic-Dogger volcanic- and volcani-clastic series. The coals at the base of the Jurassic units are characterized by higher Ba, Th, Zr, and Cr-Ni and lower S values than those at the top of the units, indicating, in general, laterally consistent trace <span class="hlt">element</span> contents. The vertical distribution of trace <span class="hlt">elements</span> in individual coal seams is also rather consistent. The B contents of coals from the Godul and Norsun areas vary from 1.5 to 4.3 ppm whereas those from the Alansa area are in the range of 95 to 138 ppm. This suggests that the coals in the Godul and Norsun areas were deposited in a swamp environment inundated by the sea from time to time, whereas coals of the Alansa were deposited in a saline environment.</p> <div class="credits"> <p class="dwt_author">Cebi, F.H.; Korkmaz, S.; Akcay, M. [Karadeniz Technical University, Trabzon (Turkey). Dept. of Geological Engineering</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">122</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70013127"> <span id="translatedtitle">Characterization of the Sukinda and Nausahi ultramafic complexes, Orissa, India by platinum-group <span class="hlt">element</span> <span class="hlt">geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Samples of 20 chromitite, 14 ultramafic and mafic rock, and 9 laterite and soil samples from the Precambrian Sukinda and Nausahi ultramafic complexes, Orissa, India were analyzed for platinum-group <span class="hlt">elements</span> (PGE). The maximum concentrations are: palladium, 13 parts per billion (ppb); platinum, 120 ppb; rhodium, 21 ppb; iridium, 210 ppb; and ruthenium, 630 ppb. Comparison of chondrite-normalized ratios of PGE for the chromitite samples of lower Proterozoic to Archean age with similar data from Paleozoic and Mesozoic ophiolite complexes strongly implies that these complexes represent Precambrian analogs of ophiolite complexes. This finding is consistent with the geology and petrology of the Indian complexes and suggests that plate-tectonic and ocean basin developement models probably apply to some parts of Precambrian shield areas. ?? 1985.</p> <div class="credits"> <p class="dwt_author">Page, N.J.; Banerji, P.K.; Haffty, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">123</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70014569"> <span id="translatedtitle">Platinum-group <span class="hlt">element</span> <span class="hlt">geochemistry</span> of zoned ultramafic intrusive suites, Klamath Mountains, California and Oregon.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Analyses for platinum-group <span class="hlt">elements</span> of the varied rock suites of three Alaskan-type ultramafic to mafic multi-intrusive bodies are reported. Ir and Ru are less than analytical sensitivities of 100 and 20 ppb; Rh is less than or near 1 ppb. Average Pd assays vary among the rocks within intrusive complexes and between the three complexes (6.3, 13.7, 36.4 ppb); average Pt assays vary little among the same samples (27.9, 60.9, 34.0 ppb). Statistically adjusted Pt/(Pt + Pd) ratios increase in each suite from gabbro through clinopyroxenite to olivine-rich rocks, possibly owing to Pd fractionation.-G.J.N.</p> <div class="credits"> <p class="dwt_author">Gray, F.; Page, N.J.; Carlson, C.A.; Wilson, S.A.; Carlson, R.R.</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">124</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/ofr20071047SRP078"> <span id="translatedtitle">Major, trace <span class="hlt">element</span> and stable isotope <span class="hlt">geochemistry</span> of synorogenic breccia bodies, Ellsworth Mountains, Antarctica</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Cambrian carbonates in the Heritage Range of the Ellsworth Mountains, West Antarctica host a series of carbonate-rich breccia bodies that formed contemporaneously with the Permian Gondwanide orogen. The breccia bodies had a three-stage genesis, with the older breccias containing Cambrian limestone (and marble) clasts supported by calcite, whereas the younger breccias are nearly clast-free and composed entirely of matrix calcite. Breccia clasts, calcite matrix and detrital matrix samples were analyzed using x-ray fluorescence (major and trace <span class="hlt">elements</span>), x-ray diffraction, and stable isotopes (C, O) and suggest that the breccias formed as part of a closed geochemical system, at considerable depth, within the Cambrian limestone host as the Ellsworth Mountains deformed into a fold-and-thrust belt along the margin of Gondwana</p> <div class="credits"> <p class="dwt_author">Craddock, J.P.; McGillion, M.S.; Webers, G.F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">125</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JAfES.100..335M"> <span id="translatedtitle">Redox control on trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> and provenance of groundwater in fractured basement of Blantyre, Malawi</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Assessment of redox state, pH, environmental isotope ratios (?18O, ?2H) coupled with PHREEQC speciation modeling investigations were conducted to understand trace <span class="hlt">element</span> geochemical controls in basement complex aquifer in Blantyre, Malawi. Groundwater in the area is typical Ca-Mg-Na-HCO3 type suggesting more of carbonate weathering and significance of carbon dioxide with dissolution of evaporites, silicate weathering and cation exchange being part of the processes contributing to groundwater mineralization. The significance of pH and redox status of groundwater was observed. The groundwater redox state was mostly O2-controlled with few exceptions where mixed (oxic-anoxic) O2-Mn(IV) and O2-Fe(III)/SO4 controlled redox states were modeled. More so, some of the main trace <span class="hlt">element</span> species modeled with PHREEQC varied with respect to pH. For instance vanadium(III) and vanadium(IV) decreased with increase in field pH contrasting the trend observed for vanadium(V). The isotopic composition of the sampled groundwater varied between -5.89‰ and -3.32‰ for ?18O and -36.98‰ and -20.42‰ for ?2H. The ?2H/?18O and ?18O/Cl- ratios revealed that groundwater is of meteoric origin through vertical recharge and mixing processes. The d-excess value approximated the y-intercept of GMWL of 10 (d-excess = 9.269, SD = 1.240) implying that influence of secondary evaporative processes on isotopic signature of the study area is minimal. Thus, there is evidence to suggest that groundwater chemistry in the studied aquifer is influenced by inherent processes with contribution from human activities and furthermore, the water originates from rainwater recharge. With such results, more studies are recommended to further constrain the processes involved in mineralization through isotopic fractionation investigations.</p> <div class="credits"> <p class="dwt_author">Mapoma, Harold Wilson Tumwitike; Xie, Xianjun; Zhang, Liping</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">126</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011Miner..42...39B"> <span id="translatedtitle">Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of coals from the Southern Cantabrian Zone (NW Spain): preliminary results</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Bituminous to anthracite coals from three small Stephanian intramontane coal-bearing basins (La Magdalena, Cinera-Matallana and Sabero) located along the Sabero-Gordón fault line strike-slip systems of the Southern Cantabrian Zone (SCZ) were examined. Coal rank expressed as mean vitrinite reflectance values of these Stephanian coals is in the range 0.72-3.96%. The vitrinite maceral group exceeds 72 vol. % in all of the coals. The coals are characterized by relatively variable contents of mineral matter and coal-ash. The mineral matter comprises, in the main, clay minerals, carbonates, sulphides and quartz. The coals exhibit medium-high concentrations (see for comparison Ronov et al. 1990; Kabata-Pendias, Pendias 1999; Ketris, Yudovich 2009) of the following <span class="hlt">elements</span> (in ppm): ?REE (53-205), Ba (300-900), As (11-57), Zn (<50-150), Cr (10-160), Rb (50-145), Co (5-26), Sc (2-24.6), Ce (17-99), Yb (1.3-4.5), Th (2.4-11.9) and U (1.1-8.1), Br (<1-14), Cs (<2-9), Eu (<0,3-1.5), Lu (0.11-0.85) and Sb (0.8-4.8), and relatively low concentrations of Sm (0.6-6.6) and Ta (<1-2). They are also characterised by relatively high Th/U values (1.31-2.29). LREE/HREE values fall in the range 24-44 (average - 30). In contrast, concentrations of Au, Ag, Hg, Ir, Ni, Se, Sn, Sr, and W are below detection limits for the applied INAA method. As the concentrations of <span class="hlt">elements</span> are significantly higher in coal-ash, most are likely related to mineral matter in the coals.</p> <div class="credits"> <p class="dwt_author">Botor, Dariusz</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">127</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFM.V53E..02P"> <span id="translatedtitle">Elucidating the construction of the Austurhorn Intrusion, SE Iceland, using zircon <span class="hlt">elemental</span> and isotopic <span class="hlt">geochemistry</span> and geochronology</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Austurhorn Intrusive Complex (AIC) in SE Iceland comprises large bodies of granophyre, gabbro, and a mafic-felsic composite zone (MFCZ) that exemplifies mafic-felsic interactions common in Icelandic silicic systems. However, despite being one of Iceland's best-studied intrusions (Blake 1966; Furman et al 1992a,b; Thorarinsson & Tegner 2009), few studies have included detailed analyses of zircon, a mineral widely recognized as a valuable tracer of the history and evolution of its parental magma(s). In this study, we employ in-situ zircon <span class="hlt">elemental</span> and isotopic (hafnium and oxygen) <span class="hlt">geochemistry</span>, as well as U-Pb geochronology, as tools for elucidating the complex construction and magmatic evolution of Austurhorn's MFCZ. The <span class="hlt">elemental</span> compositions of AIC zircons form a broad but coherent array partly overlapping with the zircon geochemical signature for Icelandic silicic volcanic rocks (Carley et al 2011). With some exceptions (see below), Hf concentrations are low (less than 10,000 ppm), typical of Icelandic zircon, and Ti concentrations range from 6 to 25 ppm (Ti-in-zircon temps. 730-870°C). Their ?18O values are generally well-constrained at +2.5 to +4 ‰, consistent with other Icelandic magmatic zircon (Bindeman et al 2012) and preserving evidence for partial melting of hydrothermally-altered crust as the source of silicic magmas within the Austurhorn system. Epsilon-Hf values cluster tightly at +13×1 ?-units, suggesting a single source for the different units of the MFCZ. The notable exceptions to the trends described above are zircons from a high-silica granophyre displaying CL-dark zones and convoluted zoning. These fall well outside the AIC geochemical arrays, primarily distinguished by high Hf (up to 24,000 ppm) and lower Ti (down to 2 ppm), far higher Hf and lower Ti than any other analyzed Icelandic zircon, and extremely low ?18O values (down to -6 ‰). We interpret these to reflect multiple episodes of partial melting and melt extraction of the same unit. In-situ (SHRIMP) dating of zircons yields a pooled age of 6.43×0.04 Ma for the MFCZ. However, a relatively high MSWD (1.6) suggests real spread in ages ranging from ~6.3 to 6.6 Ma, corroborating field evidence for the construction of the MFCZ by repeated mafic and felsic intrusions and periodic re-melting and rejuvenation of mush-like material within the complex, over a ~250 k.y. span.</p> <div class="credits"> <p class="dwt_author">Padilla, A. J.; Miller, C. F.; Carley, T. L.; Economos, R. C.; Schmitt, A. K.; Fisher, C. M.; Hanchar, J. M.; Bindeman, I. N.; Wooden, J. L.; Sigmarsson, O.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">128</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/324600"> <span id="translatedtitle">Coal-forming environments and <span class="hlt">geochemistry</span> of minor and trace <span class="hlt">elements</span> of Cretaceous coals in Pingzhuang Basin, Inner Mongolia, China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Pingzhuang Basin is a semi-grabenal fault basin of early Mesozoic age in China. Yuanbaoshan Formation of Lower Cretaceous is the main coal measure of the basin. The thickness of coal seams and the number of coal seams in each mining area vary through out the basin. The main coal-forming environments of the basin are lacustrine, lake-margin-fan-delta, lake-margin-delta, alluvial fan and fluvial faces. The coal-forming environment of different mining areas and seams in the basin varies. Ershijiazi Mining Area, which is located in the northeastern part of the basin, is mainly forefan-marsh and lakeside coal-formation; Silongtougou Mining Area, which is located in the southwestern part of the basin, is mainly lake-margin-delta coal-formation; Gushan Mining Area and West Open Pit Mining Area, which is located in the center of the basin, are mainly lakeside, lake-margin-delta-plain, lake-margin-fan-delta coal-formation. The distribution of <span class="hlt">element</span> contents of coals in different mining areas and seams differs. At Silongtougou, the contents of most minor and trace <span class="hlt">elements</span> are low except strontium. At Ershijiazi, the contents of some <span class="hlt">elements</span>, such as Fe, Co, Ni, As, Sb, Sc, Cs and U, are high in the basin, and the contents of Ba, Sr and Hf are low. At West Open Pit, the contents of most <span class="hlt">elements</span>, such as Fe, Zn, Co, Ni, As, Sb, K, Sc, Cs, Zr, U and Hf, are stable in the different seams, and the contents of these <span class="hlt">elements</span> are intermediate in the basin. The contents of other <span class="hlt">elements</span> in the area are low. At Gushan, the contents of all <span class="hlt">elements</span> in seam 5 are low, and in seam 6 are high. The <span class="hlt">elements</span> similar in geochemical characteristics have good correlation. The main correlated <span class="hlt">elements</span> are due to the formations of the organic molecular structures of coals and/or the formations of inorganic minerals in coals. The rare-<span class="hlt">earth-element</span> (REE) contents of coals in different mining areas and seams also differ, but the REE distribution patterns of all coals are alike. This indicates that the coal-forming conditions of the basin are stable. There is a good relationship between the contents of minor and trace <span class="hlt">elements</span> and the coal-forming environments.</p> <div class="credits"> <p class="dwt_author">Shao, J. [China Univ. of Mining and Technology, Beijing (China). Beijing Graduate School; Wang, Y.; Gao, C. [Liaoning Univ. of Engineering and Technology (China)</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-12-31</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">129</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49493408"> <span id="translatedtitle">Effects of the accumulation of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> on soil macrofauna community</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The accumulation of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in soil has occurred due to the pollution caused by the exploitation of rare <span class="hlt">earth</span> resources and the wide rare <span class="hlt">earth</span> fertilizers in agriculture. The accumulation of REEs has a toxic effect on the soil macrofauna community. 12 study samples were collected near a mine tailings dam with a large amount of REEs</p> <div class="credits"> <p class="dwt_author">Jinxia LI; Mei HONG; Xiuqin YIN; Jiliang LIU</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">130</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16.5328M"> <span id="translatedtitle">Geochemical behavior of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and other trace <span class="hlt">elements</span> in the Amazon River</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rivers transport large amounts of dissolved and suspended particulate material from the catchment area to the oceans and are a major source of trace metals to seawater. The Amazon River is the world's largest river and supplies approximately 20% of the oceans' freshwater (Molinier et al., 1997). However, the behavior of trace <span class="hlt">elements</span>, especially particle-reactive <span class="hlt">elements</span> such as the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE), within the river as well as in the estuary is not well constrained and rather little is known about their transport mechanisms. This study aims at understanding the transport properties of particle-reactive <span class="hlt">elements</span> in the Amazon River and some of its major tributaries, including the Rio Solimões, Rio Negro, Tapajos, Xingu and Jari Rivers. Samples were taken at 12 stations, seven of which were located in the Amazon mainstream, while the other five stations sampled its tributaries. To account for the effects of variable discharge, the samples were collected during periods of high and low discharge. We present data for major and trace <span class="hlt">elements</span>, including REE, of the dissolved and suspended load of these samples. First results indicate that the shale-normalized REE pattern of the dissolved load (filtered through 0.2 µm membranes) of the Amazon mainstream and the Rio Solimões confirm earlier studies (Elderfield et al., 1990; Gerard et al., 2003) and show an enrichment of the middle REE relative to the light and heavy REE (LaSN/GdSN: 0.25 - 0.32; GdSN/YbSN: 1.54 - 1.78). In contrast to the Amazon mainstream and the Rio Solimões, which are considered to be whitewater rivers, blackwater rivers, such as the Rio Negro, have a flat REE pattern with higher REE concentrations than whitewater rivers. The third water-type found in the Amazon Basin is clearwater, e.g. Rio Tapajos, with REE patterns in between those of the other two types, i.e. LaSN/GdSN: 0.55 - 0.70; GdSN/YbSN: 1.26 - 1.55. A similar behavior can be identified for other major and trace <span class="hlt">elements</span>. While <span class="hlt">elements</span> such as Ca, Mg, Sr or U are relatively high in whitewater rivers, their concentrations are generally lower in clearwater rivers and lowest in blackwater rivers. In contrast, <span class="hlt">elements</span> including Si, Rb and Cs have their highest concentrations in blackwater rivers, intermediate concentrations in clearwater rivers and their lowest concentrations in whitewater river. [1] Elderfield H., Upstill-Goddard R. and Sholkovitz E.R. (1990): The rare <span class="hlt">earth</span> <span class="hlt">elements</span> in rivers, estuaries and coastal seas and their significance to the composition of ocean waters. Geochim.Cosmochim.Acta, 54, 971-991 [2] Gerard M., Seyler P., Benedetti M.F., Alves V.P., Boaventura G.R. and Sondag, F. (2003): Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Amazon basin. Hydrological Processes, 17, 1379-1392 [3] Molinier M., Guyot J.L., Callede J., Guimaraes V., Oliveira E. and Filizola N. (1997): Hydrologie du bassinamazonien. Evironment et développement en Amazonie brésiliènne, Thery H. (ed.), Berlin Publ., Paris; 24-41</p> <div class="credits"> <p class="dwt_author">Merschel, Gila; Bau, Michael; Dantas, Elton Luiz</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">131</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.V54A..02H"> <span id="translatedtitle">Deciphering The Sources Of Cenozoic Volcanism In Central Mongolia Using Trace <span class="hlt">Element</span> And Isotope <span class="hlt">Geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">One of the largest regions of Cenozoic intra-plate volcanism stretches across central Asia from the Baikal Rift in Siberia, through central Mongolia to China. In Mongolia this is expressed as numerous small-volume alkali-basaltic cones and lavas, erupted since ca. 30 Ma. Currently, accepted models of melt generation for intraplate magmatism, such as mantle plumes, lithospheric extension and convective removal of the lithosphere, are difficult to reconcile with some aspects of volcanism and tectonics in this region. A suite of basalts erupted across an area of Cenozoic uplift in central Mongolia, known as the Hangai Dome, has been analysed for trace <span class="hlt">elements</span> and Sr-Nd-Pb isotopes. New Pb isotope data were collected by double spike MC-ICP-MS at the Open University and have a long-term 2? reproducibility better than 175 ppm for NBS 981. These data suggest progressive mixing between two distinct source regions in the genesis of the Hangai basalts. Older basalts, previously dated at 5.91 ± 0.02 Ma (Barry et al., 2003), are derived from a component with an asthenospheric signature similar to depleted Indian MORB. Younger basalts are increasingly mixed with a component with lower Pb and Sr ratios and an enriched trace <span class="hlt">element</span> signature, which is similar in composition to some lamproites erupted in the western USA (Mirnejad and Bell, 2006). This represents a transition from asthenospheric to lithospheric melting through time. Furthermore, studies on mantle xenoliths from across the Hangai Dome indicate an elevated geotherm under the centre of the dome and significantly cooler conditions at its margins, interpreted to be the result of mantle upwellling (Harris et al., in review). Further numerical modelling will assess the relative contributions from lithospheric and asthenospheric sources in the genesis of these basalts, and contribute to understanding this enigmatic volcanic region. Barry, T. L., Saunders, A. D., Kempton, P. D., Windley, B.F., Pringle, M.S., Dorjnamjaa, D. and Saander, S. (2003)., J. Petrol. 44 55-91 Harris, N., Hunt, A., Parkinson, I., Tindle, A., Yondon, M. and Hammond, S. (2009) in review Mirnejad, H. And Bell, K (2006)., J. Petrol. 47 2463-2489</p> <div class="credits"> <p class="dwt_author">Hunt, A. C.; Parkinson, I. J.; Harris, N.; Rogers, N. W.; Barry, T.; Yondon, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">132</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40927505"> <span id="translatedtitle">Origin of middle rare <span class="hlt">earth</span> <span class="hlt">element</span> enrichments in acid waters of a Canadian High Arctic lake</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">–Middle rare <span class="hlt">earth</span> <span class="hlt">element</span> (MREE) enriched rock-normalized rare <span class="hlt">earth</span> <span class="hlt">element</span> (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</p> <div class="credits"> <p class="dwt_author">Kevin H Johannesson; Xiaoping Zhou</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">133</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014MinDe..49.1013H"> <span id="translatedtitle">Geochemical prospecting for rare <span class="hlt">earth</span> <span class="hlt">elements</span> using termite mound materials</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Blockspruit fluorite prospect, located in North West State of the Republic of South Africa, occurs within an actinolite rock zone that was emplaced into the Kenkelbos-type granite of Proterozoic age. There are a large number of termite mounds in the prospect. For geochemical prospecting for rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs), in total, 200 samples of termite mound material were collected from actinolite rock and granite zones in the prospect. Geochemical analyses of these termite mound materials were conducted by two methods: portable X-ray fluorescence (XRF) spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS). Comparison of the two methods broadly indicates positive correlations of REEs (La, Ce, Pr, Nd, and Y), in particular Y and La having a strong correlation. As the result of modal abundance analyses, the actinolite rock at surface mainly consists of ferro-actinolite (89.89 wt%) and includes xenotime (0.26 wt%) and monazite (0.21 wt%) grains as REE minerals. Termite mound materials from actinolite rock also contain xenotime (0.27 wt%) and monazite (0.41 wt%) grains. In addition, termite mound materials from the actinolite rock zone have high hematite and Fe silicate contents compared to those from granite zone. These relationships suggest that REE minerals in termite mound materials originate form actinolite rock. Geochemical anomaly maps of Y, La, and Fe concentrations drawn based on the result of the portable XRF analyses show that high concentrations of these <span class="hlt">elements</span> trend from SW to NE which broadly correspond to occurrences of actinolite body. These results indicate that termite mounds are an effective tool for REE geochemical prospection in the study area for both light REEs and Y, but a more detailed survey is required to establish the distribution of the actinolite rock body.</p> <div class="credits"> <p class="dwt_author">Horiuchi, Yu; Ohno, Tetsuji; Hoshino, Mihoko; Shin, Ki-Cheol; Murakami, Hiroyasu; Tsunematsu, Maiko; Watanabe, Yasushi</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">134</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/14582968"> <span id="translatedtitle">Effects of spraying rare <span class="hlt">earths</span> on contents of rare <span class="hlt">Earth</span> <span class="hlt">elements</span> and effective components in tea.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> (RE) fertilizer is widely applied in China to increase the yield and the quality of crops including tea. However, the effects of spraying RE fertilizer on the contents of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) and effective components in tea are unknown. The results from basin and field experiments show that the values of the REE concentrations in new shoots of tea plants and the concentration of REE in the soil (REE/REEs) either from control basins or from treatment basins were smaller than those in other parts of tea plant and similar between control and treatment. The longer the interval between spraying RE fertilizer and picking the shoots of tea plants, the less the effects from spraying. About 80% summation operator REE (the sum of the concentrations of 15 REE) in tea, whether it came from spraying or not, was insoluble in the infusion. About 10% the soluble REE of summation operator REE in tea infusion was bound to polysaccharide, and the amount of REE bound polysaccharide decreased over time. At least a 25 day safety interval is needed between spraying and picking if the microelement fertilizer is used, in order to enhance tea output and to ensure tea safety. PMID:14582968</p> <div class="credits"> <p class="dwt_author">Wang, Dongfeng; Wang, Changhong; Ye, Sheng; Qi, Hongtao; Zhao, Guiwen</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">135</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012Litho.153..278B"> <span id="translatedtitle">The sources of energy for crustal melting and the <span class="hlt">geochemistry</span> of heat-producing <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Crustal melting to produce granite magmas requires a tremendous amount of energy. In principle, there are three main mechanisms of heating that can extensively melt a fertile crust: radiogenic heat caused by the decay of 40K, 230Th, 235U and 238U; increased subcrustal heat flux caused by the upwelling of deeper, therefore hotter, mantle materials; advection of heat caused by the emplacement and crystallization of hot mantle magmas. Two-dimensional finite <span class="hlt">elements</span> modeling reveals that a fertile crust thickened to 65-70 km would produce copious granite magmatism after 30-40 M.y. if its average heat-production is A > 1.2 ?W m- 3, but it would scarcely melt if A < 0.65 ?W m- 3. Increasing the subcrustal heat flow from the normal value of QM ? 0.025 W m- 2 to QM ? 0.04 W m- 2 may also lead to extensive crustal melting, especially if the crust does not thin to less than 30-35 km. Very high QM (? 0.06 W m- 2) affecting the continental crust is unlikely, but the combination of moderately high QM (? 0.04 W m- 2) and a thick fertile crust with A < 1.2 ?W m- 3, such as often happens in the volcanic and back-arc areas of subduction zones, is ideal to produce copious granite magmatism. Lastly, the emplacement of hot mantle magmas in a fertile crust can produce crustal melts in just a few thousand years, but the volume of these is equal to or less than the volume of the intruding magma. A clue for understanding the relative importance of each of these three mechanisms comes from the radiogenic heat production of granite rocks calculated from the concentration of 40K, 230Th, 235U and 238U at the time of their formation. This parameter estimated on more than 3400 granites samples of different ages and provenance reveals a strongly asymmetric distribution peaking around 2.4 ?W m- 3, a value much higher than the average continental crust (about 1-1.2 ?W m- 3) and certainly much higher than the average lower continental crust (about 0.4-0.8 ?W m- 3). Only those granite rock types that are clearly connected with mantle heat sources such as the Archean TTG, post-Archean subduction-related trondhjemites, and recent adakites have a heat production equal to or smaller than the lower continental crust. Since the bulk melt/solid partition coefficient of the heat-producing <span class="hlt">elements</span> (HPE: K, Th and U) is k ? 1, the elevated HPE contents of granites indicates that most of them have been derived from HPE-rich sources. We conclude that radiogenic heating is often essential, and always advantageous, for generating large volumes of granite magmas, and that granite magmatism is the main cause of the accumulation of HPE in the upper crust.</p> <div class="credits"> <p class="dwt_author">Bea, Fernando</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">136</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003GeCoA..67.3717D"> <span id="translatedtitle">Pb-Sr-He isotope and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the Cape Verde Archipelago</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">New lead, strontium and helium isotopic data, together with trace <span class="hlt">element</span> concentrations, have been determined for basalts from the Cape Verde archipelago (Central Atlantic). Isotopic and chemical variations are observed at the scale of the archipelago and lead to the definition of two distinct groupings, in keeping with earlier studies. The Northern Islands (Santo Antão, São Vicente, São Nicolau and Sal) present Pb isotopic compositions below the Northern Hemisphere Reference Line (NHRL) (cf. Hart, 1984), unradiogenic Sr and relatively primitive 4He/ 3He ratios. In contrast, the Southern Islands (Fogo and Santiago) display Pb isotopes above the NHRL, moderately radiogenic Sr and MORB-like helium signatures. We propose that the dichotomy between the Northern and Southern Islands results from the presence of three isotopically distinct components in the source of the Cape Verde basalts: (1) recycled ˜1.6-Ga oceanic crust (high 206Pb/ 204Pb, low 87Sr/ 86Sr and high 4He/ 3He); (2) lower mantle material (high 3He); and (3) subcontinental lithosphere (low 206Pb/ 204Pb, high 87Sr/ 86Sr and moderately radiogenic 4He/ 3He ratios). The signature of the Northern Islands reflects mixing between recycled oceanic crust and lower mantle, to which small proportions of entrained depleted material from the local upper mantle are added. Basalts from the Southern Islands, however, require the addition of an enriched component thought to be subcontinental lithospheric material instead of depleted mantle. The subcontinental lithosphere may stem from delamination and subsequent incorporation into the Cape Verde plume, or may be remnant from delamination just before the opening of the Central Atlantic. Basalts from São Nicolau reflect the interaction with an additional component, which is identified as oceanic crustal material.</p> <div class="credits"> <p class="dwt_author">Doucelance, Régis; Escrig, Stéphane; Moreira, Manuel; Gariépy, Clément; Kurz, Mark D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">137</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013GeCoA.115...46G"> <span id="translatedtitle">Isotopic and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of alkalic-mafic-ultramafic-carbonatitic complexes and flood basalts in NE India: Origin in a heterogeneous Kerguelen plume</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Archean East Indian cratonic margin was affected by the Kerguelen plume (KP) ˜117 Ma, causing flood-basalt eruptions of the Rajmahal-Bengal-Sylhet Traps (RBST). The RBST cover ˜one million km2 in and around the Bengal Basin as alkalic-ultrabasic intrusives in the west and Sikkim in the north, and Sylhet basalts and alkalic-carbonatitic-ultramafic complexes in the Shillong plateau - Mikir hills farther east of the Rajmahal-Bengal Traps. We provide new Nd-Sr-Pb-isotopic and trace <span class="hlt">element</span> data on 21 unreported discrete lava flows of the Rajmahal Traps, 56 alkalic-carbonatitic-mafic-ultramafic rocks from four alkalic complexes, and three dikes from the Gondwana Bokaro coalfields, all belonging to the RBST. The data allow geochemical correlation of the RBST with some contemporaneous Kerguelen Plateau basalts and KP-related volcanics in the southern Indian Ocean. Specifically, the new data show similarity with previous data of Rajmahal group I-II basalts, Sylhet Traps, Bunbury basalts, and lavas from the southern Kerguelen Plateau, indicating a relatively primitive KP source, estimated as: ?Nd(I) = +2, 87Sr/86Sr(I) = 0.7046, with a nearly flat time-integrated rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) pattern. We model the origin of the uncontaminated RBST basalts by ˜18% batch melting with a 2× chondritic KP source in the spinel-peridotite stability depths of 60-70 km in the mantle. The new geochemical data similar to the Rajmahal group II basalts indicate a light REE enriched average source at ?Nd(I) = -5, 87Sr/86Sr(I) = 0.7069. Our geochemical modeling indicates these lavas assimilated granulites of the Eastern Ghats, reducing the thickness of the continental Indian lithosphere. Lack of an asthenospheric MORB component in the RBST province is indicated by various trace <span class="hlt">element</span> ratios as well as the Nd-Sr isotopic ratios. Three alkalic complexes, Sung, Samchampi, and Barpung in NE India, and one in Sikkim to the north are of two groups: carbonatites, pyroxenites, lamproites, nephelinites, sovites, melteigite in the first group and syenites and ijolites in the second. The Nd-Sr-Pb-isotopic and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the first group of carbonatitic-ultrabasic rocks are consistent with similar data of the RBST lavas of the present and previous studies, and are modeled as derived from a relatively primitive carbonated garnet peridotite source in the KP. In contrast, the syenites and ijolites of the second group show a wide range of Nd-Sr-Pb isotopic compositions, modeled by low-degree melts of an ancient recycled carbonated eclogite also in the KP. The KP thus reflects heterogeneities in the lower mantle-derived plume with carbonated components yielding ultrabasic melts at greater depths with low-degree melting, followed by rise of the plume at shallower depths causing tholeiitic flood basalt volcanism. Collectively, these data imply a zone of influence of the plate-motion-reconstructed KP head for ˜1000 km around the Bengal Basin, as represented by the widely scattered and diverse rock types of the RBST.</p> <div class="credits"> <p class="dwt_author">Ghatak, Arundhuti; Basu, Asish R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">138</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20120001844&hterms=see+something+say+something&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsee%2Bsomething%2Bsay%2Bsomething"> <span id="translatedtitle">Core-Mantle Partitioning of Volatile Siderophile <span class="hlt">Elements</span> and the Origin of Volatile <span class="hlt">Elements</span> in the <span class="hlt">Earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">There are currently several hypotheses on the origin of volatile siderophile <span class="hlt">elements</span> in the <span class="hlt">Earth</span>. One hypothesis is that they were added during <span class="hlt">Earth</span> s accretion and core formation and mobilized into the metallic core [1], others claim multiple stage origin [2], while some hypothesize that volatiles were added after the core already formed [3]. Several volatile siderophile <span class="hlt">elements</span> are depleted in <span class="hlt">Earth</span> s mantle relative to the chondrites, something which continues to puzzle many scientists. This depletion is likely due to a combination of volatility and core formation. The <span class="hlt">Earth</span> s core is composed of Fe and some lighter constituents, although the abundances of these lighter <span class="hlt">elements</span> are unknown [4]. Si is one of these potential light <span class="hlt">elements</span> [5] although few studies have analyzed the effect of Si on metal-silicate partitioning, in particular the volatile <span class="hlt">elements</span>. As, In, Ge, and Sb are trace volatile siderophile <span class="hlt">elements</span> which are depleted in the mantle but have yet to be extensively studied. The metal-silicate partition coefficients of these <span class="hlt">elements</span> will be measured to determine the effect of Si. Partition coefficients depend on temperature, pressure, oxygen fugacity, and metal and silicate composition and can constrain the concentrations of volatile, siderophile <span class="hlt">elements</span> found in the mantle. Reported here are the results from 13 experiments examining the partitioning of As, In, Ge, and Sb between metallic and silicate liquid. These experiments will examine the effect of temperature, and metal-composition (i.e., Si content) on these <span class="hlt">elements</span> in or-der to gain a greater understanding of the core-mantle separation which occurred during the <span class="hlt">Earth</span> s early stages. The data can then be applied to the origin of volatile <span class="hlt">elements</span> in the <span class="hlt">Earth</span>.</p> <div class="credits"> <p class="dwt_author">Nickodem, K.; Righter, K.; Danielson, L.; Pando, K.; Lee, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">139</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFMIN13B..08L"> <span id="translatedtitle">Advancing Access, Attribution, and Integration of <span class="hlt">Earth</span> & Ocean Science Data: Integrated Services of the Marine Geoscience Data System and the Geoinformatics for <span class="hlt">Geochemistry</span> Program</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Development and operation of digital data collections are needed across all areas of the <span class="hlt">earth</span> and ocean sciences to ensure access and preservation of data sets collected in support of <span class="hlt">earth</span> and ocean sciences in order to maximize the return on research investments, while enabling verification of research results and contributing to new science initiatives. This is particularly true for data sets that are acquired at high cost, particularly in the marine environment, and that contain irreplaceable observations made of <span class="hlt">earth’s</span> dynamic properties. The Marine Geoscience Data System (MGDS, www.marine-geo.org) and the Geoinformatics for <span class="hlt">Geochemistry</span> Program (GfG, www.geoinfogeochem.org) have over the past decade developed, maintained, and operated community-driven data collections that support the preservation, discovery, retrieval, and analysis of a wide range of observational field and analytical data types from the marine and terrestrial environments, among them the PetDB database, the <span class="hlt">Earth</span>Chem data network, the Ridge2000 and MARGINS databases, the Antarctic and Southern Ocean Data System (ASODS), the Global Multi Resolution Topography Synthesis, and the System for <span class="hlt">Earth</span> Sample Registration (SESAR). MGDS and GfG systems have been developed based on an active understanding of the practices, needs, and concerns of their user communities. They have engaged investigators in the design of the systems, seeking their feedback, and educating the community about responsibilities and benefits of scientific data management and sharing, and worked with funding agencies, editors, publishers, professional societies, and researchers to achieve broad community support, to proactively drive the development of community standards and best practices for data submission, data publication, data documentation, and data archiving, and to advance implementation. In a new formal partnership named IEDA (Integrated <span class="hlt">Earth</span> Data Applications), the MGDS and GfG will be funded by the US National Science Foundation under a Cooperative Agreement to continue the operation of all MGDS and GfG data systems, while providing new integrated data services that will substantially enhance the utility of all data collection components, and improve data curation, interoperability and efficiency of operations. These will include an on-line service to improve ease of data submission across our user communities, a data publication service for scientists to publish their datasets with citable universal identifiers (DOIs), partnerships with institutions to ensure long-term archiving of data holdings, an authentication service for single sign-on to all systems, and operational services for shared vocabularies and to ease registration of common expeditions and geochemical datasets across our two systems.</p> <div class="credits"> <p class="dwt_author">Lehnert, K. A.; Carbotte, S. M.; Ferrini, V.; Arko, R. A.; Chan, S.; Ryan, W. B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">140</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014GeCoA.140...20C"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> as indicators of hydrothermal processes within the East Scotia subduction zone system</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The East Scotia subduction zone, located in the Atlantic sector of the Southern Ocean, hosts a number of hydrothermal sites in both back-arc and island-arc settings. High temperature (>348 °C) ‘black smoker’ vents have been sampled at three locations along segments E2 and E9 of the East Scotia back-arc spreading ridge, as well as ‘white smoker’ (<212 °C) and diffuse (<28 °C) hydrothermal fluids from within the caldera of the Kemp submarine volcano. The composition of the endmember fluids (Mg = 0 mmol/kg) is markedly different, with pH ranging from <1 to 3.4, [Cl-] from ?90 to 536 mM, [H2S] from 6.7 to ?200 mM and [F-] from 35 to ?1000 ?M. All of the vent sites are basalt- to basaltic andesite-hosted, providing an ideal opportunity for investigating the geochemical controls on rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) behaviour. Endmember hydrothermal fluids from E2 and E9 have total REE concentrations ranging from 7.3 to 123 nmol/kg, and chondrite-normalised distribution patterns are either light REE-enriched (LaCN/YbCN = 12.8-30.0) with a positive europium anomaly (EuCN/Eu?CN = 3.45-59.5), or mid REE-enriched (LaCN/NdCN = 0.61) with a negative Eu anomaly (EuCN/Eu?CN = 0.59). By contrast, fluids from the Kemp Caldera have almost flat REE patterns (LaCN/YbCN = 2.1-2.2; EuCN/Eu?CN = 1.2-2.2). We demonstrate that the REE <span class="hlt">geochemistry</span> of fluids from the East Scotia back-arc spreading ridge is variably influenced by ion exchange with host minerals, phase separation, competitive complexation with ligands, and anhydrite deposition, whereas fluids from the Kemp submarine volcano are also affected by the injection of magmatic volatiles which enhances the solubility of all the REEs. We also show that the REE patterns of anhydrite deposits from Kemp differ from those of the present-day fluids, potentially providing critical information about the nature of hydrothermal activity in the past, where access to hydrothermal fluids is precluded.</p> <div class="credits"> <p class="dwt_author">Cole, Catherine S.; James, Rachael H.; Connelly, Douglas P.; Hathorne, Ed C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_6");' href="#" title="Previous Page"> <img 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href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_9");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">141</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70020068"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> metasomatism in hydrothermal systems: The Willsboro-Lewis wollastonite ores, New York, USA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Wollastonite ores and garnet-pyroxene skarns in the Willsboro-Lewis district, New York, USA were formed in a complex hydrothermal system associated with the emplacement of a large anorthosite pluton. Contact-metamorphic marbles were replaced by wollastonite, garnet, and clinopyroxene during infiltration metasomatism involving large volumes of water of chiefly meteoric origin. Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) in these rocks show large departures from the protolith REE distribution, indicative of substantial REE mobility. Three types of chondrite-normalized REE distribution patterns are present. The most common, found in ores and skarns containing andradite-rich garnet, is convex-up in the light REE (LREE) with a maximum at Pr and a positive Eu anomaly. Europium anomalies and Pr/Yb ratios are correlated with X(Ad) in garnet. This pattern (type C) results from uptake of REE from hydrothermal fluids by growing crystals of calcsilicate minerals, principally andradite, with amounts of LREE controlled by the difference in ionic radius between Ca++ and REE3+ in garnet X sites. The Eu anomaly results either from prior interaction of the fluids with plagioclase-rich, Eu-positive anorthositic rocks in and near the ore zone, or by enrichment of divalent Eu on growth surfaces of garnet followed by entrapment, or both. Relative enrichment in heavy REE (type H) occurs in ores and skarn where calcsilicates, including grossularitic garnet, in contact-metamorphic marble have been concentrated by dissolution of calcite. In most cases a negative Eu anomaly is inherited from the marble protolith. Skarns containing titanite and apatite exhibit high total REE, relative light REE enrichment, and negative Eu anomalies (type L). These appear to be intrusive igneous rocks (ferrodiorites or anorthositic gabbros) that have been converted to skarn by Ca metasomatism. REE, sequestered in titanite, apatite, and garnet, preserve the approximate REE distribution pattern of the igneous protolith. Post-ore granulite facies metamorphism homogenized zoned mineral grains without causing complete intergranular reequilibration and does not appear to have significantly affected the whole-rock REE distributions. These results demonstrate that extensive REE metasomatism can occur in hydrothermal systems at shallow to intermediate depths and that REE <span class="hlt">geochemistry</span> may be useful in discerning the origin of skarns and skarn-related ore deposits.</p> <div class="credits"> <p class="dwt_author">Whitney, P.R.; Olmsted, J.F.</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">142</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4260943"> <span id="translatedtitle">Recovery and Separation of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> Using Salmon Milt</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Recycling rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) used in advanced materials such as Nd magnets is important for the efficient use of REE resources when the supply of several REEs is limited. In this work, the feasibility of using salmon milt for REE recovery and separation was examined, along with the identification of the binding site of REEs in salmon milt. Results showed that (i) salmon milt has a sufficiently high affinity to adsorb REEs and (ii) the adsorption capacity of the milt is 1.04 mEq/g, which is comparable with that of commercial cation exchange resin. Heavier REEs have higher affinity for milt. A comparison of stability constants and adsorption patterns of REEs discussed in the literature suggests that the phosphate is responsible for the adsorption of REE in milt. The results were supported by dysprosium (Dy) and lutetium (Lu) LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. The REE-P shell was identified for the second neighboring atom, which shows the importance of the phosphate site as REE binding sites. The comparison of REE adsorption pattern and EXAFS results between the milt system and other adsorbent systems (cellulose phosphate, Ln-resin, bacteria, and DNA-filter hybrid) revealed that the coordination number of phosphate is correlated with the slope of the REE pattern. The separation column loaded with milt was tested to separate REE for the practical use of salmon milt for the recovery and separation of REE. However, water did not flow through the column possibly because of the hydrophobicity of the milt. Thus, sequential adsorption–desorption approach using a batch-type method was applied for the separation of REE. As an example of the practical applications of REE separation, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste by a batch-type method using salmon milt. PMID:25490035</p> <div class="credits"> <p class="dwt_author">Takahashi, Yoshio; Kondo, Kazuhiro; Miyaji, Asami; Watanabe, Yusuke; Fan, Qiaohui; Honma, Tetsuo; Tanaka, Kazuya</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">143</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013PhDT.........6M"> <span id="translatedtitle">Nanomaterials made of <span class="hlt">earth</span>-abundant <span class="hlt">elements</span> for photovoltaics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">elements</span> 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 <span class="hlt">earth</span>-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.</p> <div class="credits"> <p class="dwt_author">Molk, Doreen</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">144</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014CoMP..167.1002S"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of ultrahigh-pressure anatexis: fractionation of <span class="hlt">elements</span> in the Kokchetav gneisses during melting at diamond-facies conditions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K2O and an increase in FeO + MgO in the restites. The most characteristic trace <span class="hlt">element</span> feature of the Kokchetav UHP restites is a strong depletion in light rare <span class="hlt">earth</span> <span class="hlt">elements</span> (LREE), Th and U. This is attributed to complete dissolution of monazite/allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to ~1,000 °C. Large ion lithophile <span class="hlt">elements</span> (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace <span class="hlt">element</span> fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.</p> <div class="credits"> <p class="dwt_author">Stepanov, Aleksandr S.; Hermann, Joerg; Korsakov, Andrey V.; Rubatto, Daniela</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">145</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70010754"> <span id="translatedtitle">Biogeochemistry of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> with particular reference to hickory trees</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Hickory trees concentrate the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in their leaves to a phenomenal degree and may contain as much as 2300 p.p.m. of total rare <span class="hlt">earths</span> based on the dry weight of the leaves. The average proportions of the individual <span class="hlt">elements</span> (atomic percent of the total rare-<span class="hlt">earth</span> <span class="hlt">elements</span>) in the leaves are: Y 36, La 16, Ce 14, Pr 2, Nd 20, Sm 1, Eu 0.7, Gd 3, Tb 0.6, Dy 3, Ho 0.7, Er 2, Tm 0.2, Yb 1, and Lu 0.2. The similarity in the proportions of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in the leaves and in the exchange complex of the soil on which the hickory trees grow indicates that the trees do not fractionate the rare <span class="hlt">earths</span> appreciably. The variation of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in the leaves and soils can be explained generally in terms of the relative abundance of the cerium group and the yttrium group, except for the <span class="hlt">element</span> cerium. The large fluctuations in the proportion of cerium [Ce/(La + Nd) atomic ratios of 0.16 to 0.86] correlate with oxidation-reduction conditions in the soil profile. The substitution of dilute H2SO3 for dilute HC1 in the determination of available rare-<span class="hlt">earth</span> <span class="hlt">elements</span> brings about a large increase in the proportion of cerium that is extracted from an oxygenated subsoil. These relationships strongly suggest that quadrivalent cerium is present in oxygenated subsoil and is less available to plants than the other rare-<span class="hlt">earth</span> <span class="hlt">elements</span> that do not undergo such a change in valence. A few parts per billion of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> have been detected in two samples of ground water. ?? 1958.</p> <div class="credits"> <p class="dwt_author">Robinson, W.O.; Bastron, H.; Murata, K.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1958-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">146</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=251706"> <span id="translatedtitle">RARE <span class="hlt">EARTH</span> <span class="hlt">ELEMENTS</span>: A REVIEW OF PRODUCTION, PROCESSING, RECYCLING, AND ASSOCIATED ENVIRONMENTAL ISSUES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) are a group of 15 chemical <span class="hlt">elements</span> in the periodic table, specifically the lanthanides. Two other <span class="hlt">elements</span>, scandium and yttrium, have a similar physiochemistry to the lanthanides, are commonly found in the same mineral assemblages, and are often refe...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">147</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21062438"> <span id="translatedtitle">Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span>: A Tool for Understanding the Behaviour of Trivalent Actinides in the Geosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations have been determined in groundwaters, granite and fracture fillings in a restored uranium mine. The granitoids normalized REE patterns of groundwaters show heavy rare <span class="hlt">earth</span> <span class="hlt">elements</span> (HREE)-enrichment and positive Eu anomalies. This suggests that the REE are fractionated during leaching from the source rocks by groundwaters. Preferential leaching of HREE would be consistent with the greater stability of their aqueous complexes compared to those of the light rare <span class="hlt">earth</span> <span class="hlt">elements</span> (LREE), together with the dissolution of certain fracture filling minerals, dissolution/alteration of phyllosilicates and colloidal transport. (authors)</p> <div class="credits"> <p class="dwt_author">Buil, Belen; Gomez, Paloma; Garralon, Antonio; Turrero, M. Jesus [Medioambiente, CIEMAT, Avda. Complutense 22, Madrid, 28040 (Spain)</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">148</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006AGUFM.B33A1150P"> <span id="translatedtitle">Modelling of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> Complexation With Humic Acid</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The binding of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) to humic acid (HA) was studied by combining Ultrafiltration and ICP- MS techniques. REE-HA complexation experiments were performed at various pH conditions (ranging from 2 to 10.5) using a standard batch equilibration method. Results show that the amount of REE bound to HA strongly increase with increasing pH. Moreover, a Middle REE (MREE) downward concavity is evidenced by REE distribution patterns at acidic pH. Modelling of the experimental data using Humic Ion Binding Model VI provided a set of log KMA values (i.e. the REE-HA complexation constants specific to Model VI) for the entire REE series. The log KMA pattern obtained displays a MREE downward concavity. Log KMA values range from 2.42 to 2.79. These binding constants are in good agreement with the few existing datasets quantifying the binding of REE with humic substances except a recently published study which evidence a lanthanide contraction effect (i.e. continuous increase of the constant from La to Lu). The MREE downward concavity displayed by REE-HA complexation pattern determined in this study compares well with results from REE-fulvic acid (FA) and REE-acetic acid complexation studies. This similarity in the REE complexation pattern shapes suggests that carboxylic groups are the main binding sites of REE in HA. This conclusion is further supported by a detailed review of published studies for natural, organic-rich, river- and ground-waters which show no evidence of a lanthanide contraction effect in REE pattern shape. Finally, application of Model VI using the new, experimentally determined log KMA values to World Average River Water confirms earlier suggestions that REE occur predominantly as organic complexes (> 60 %) in the pH range between 5-5.5 and 7-8.5 (i.e. in circumneutral pH waters). The only significant difference as compared to earlier model predictions made using estimated log KMA values is that the experimentally determined log KMA values predict a significantly higher amount of Light REE bound to organic matter under alkaline pH conditions. Taken as a whole, the new experimental results shed additional light on the processes that govern REE pattern shapes in natural, organic-rich waters.</p> <div class="credits"> <p class="dwt_author">Pourret, O.; Davranche, M.; Gruau, G.; Dia, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">149</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUSM.B41A..02R"> <span id="translatedtitle">Rare <span class="hlt">Earth</span> <span class="hlt">elements</span> as sediment tracers in Mangrove ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> have been widely used as geochemical source fingerprints of rocks and sediments to study processes involving cosmo-chemistry, igneous petrology, tectonic setting and for investigations of water-rock interactions and weathering processes including transport of weathering products to the oceans.Many studies have addressed the use of REEs in investigating the environmental impact of human activity and demonstrated that the REE natural distribution in sediment from densely industrialised and populated regions can be altered by anthropogenic influences.The coastal wetlands like Mangroves are ultimate sinks for all the material derived from the terrestrial and marine environment.The high productivity and low ratio of sediment respiration to net primary production gives mangrove sediments the potential for long-term sequestration of these pollutants/metals before reaching the coastal ocean. Geochemical study of REE in these sedimentary systems is useful for determining the nature of the biogeochemical processes. In particular, REE show a great sensitivity to pH changes, redox conditions and adsorption/ desorption reactions. So, they may be used as markers of discharge provenance, weathering processes, changes in environmental conditions in the water and sediments of Mangrove/wetland systems. Our study aims to establish the abundance, distribution and enrichment of REEs to track the sediment sources and biogeochemical processes occurring in the mangrove environment.Core sediments were collected from the different environmental settings within the Pichavaram mangrove area.Higher REE concentration in Pichavaram sediments indicated greater input from sources like terrestrial weathering and anthropogenic activities which in turn are affected by saline mixing and dynamic physico-chemical processes occurring in the mangrove environment. REE enrichment order was attributed to the alkaline pH (7-8.5) and reducing conditions prevailing in the mangrove environments leading to preferential removal of MREE and LREE by adsorption and precipitation as Fe-Mn oxy-hydroxides in sediments. PAAS normalised plots also depicted slightly convex sub-parallel shale like patterns with alike enrichment.The same characteristics have been observed for sediments for Kaveri River validating that the sediments brought down during fluvial transport, is the source of REE in Pichavaram. Strong positive Eu anomalies suggested prevalence of reducing conditions as well as it indicated source from the natural weathering of the post Archean charnockitic and gneissic terrain in the course of river Kaveri. Role of different mangroves species in controlling the REE distribution in sediments was also observed . Tidally influenced cores showed complexity of environment these sites were exposed to. Factor analysis delineated three main processes controlling REE distribution in Pichavaram, namely natural weathering, inherent physico-chemical processes and in-situ biogeochemical processes occurring in this hypersaline mangrove environment.</p> <div class="credits"> <p class="dwt_author">Ramanathan, A. L.; Swathi, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">150</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1985JGR....90.8743C"> <span id="translatedtitle">Trace <span class="hlt">element</span> and isotopic <span class="hlt">geochemistry</span> of lavas from Haleakala Volcano, east Maui, Hawaii: Implications for the origin of Hawaiian basalts</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Haleakala volcano on East Maui, Hawaii, consists of a tholeiitic basalt shield which grades into a younger alkalic series that was followed by a posterosional alkalic series. Tholeiitic, transitional, and alkalic basalts range widely in Sr and Nd isotopic ratios (from mid-ocean ridge basalt to bulk <span class="hlt">earth</span> ratios) and incompatible <span class="hlt">element</span> (P, K, Rb, Sr, Zr, Nb, Ba, REE, Hf, Ta, and Th) abundances, but isotopic ratios and incompatible <span class="hlt">element</span> abundance ratios (e.g., Ba/La, Nb/La, La/Ce, La/Sm) vary systematically with age. The youngest series (posterosional alkalic lavas) has the highest Rb/Sr, Ba/La, Nb/La, La/Ce, and 143Nd/144Nd ratios and the lowest 87sr/86sr ratios, whereas the oldest series (dominantly tholeiitic basalts) has the lowest Rb/Sr, Ba/La, Nb/La, La/Ce, and 143Nd/144Nd ratios and the highest 87sr/86sr ratios. The most striking features of the trace <span class="hlt">element</span> and isotopic data are the inverse correlations between isotopic ratios and parent/daughter abundance ratios in the Sr and Nd systems. Although some of the geochemical variations can be explained by shallow level fractional crystallization (e.g., alkali basalt to mugearite [Chen et al., 1984, and manuscript in preparation, 1985]), the temporal geochemical trends require a major role for mixing. We propose a model in which melts from a diaper interact with incipient melts of its wall rocks, presumed to be oceanic lithosphere. Because of motion between the lithosphere and mantle hot spot the relative contribution of melts from the diapir (mantle plume) material to the lavas decreases with time; consequently, with decreasing age the basalts become more enriched in incompatible trace <span class="hlt">elements</span> and acquire Sr and Nd isotopic ratios which overlap with mid-ocean ridge basalts. This model quantitatively explains the isotopic ratios and incompatible trace <span class="hlt">element</span> abundances in representative samples from the three Haleakala volcanic series. On the basis of the degrees of melting inferred for the mixing components we conclude that the lower lithosphere and much of the asthenosphere beneath Hawaiian volcanoes are involved in creating these volcanoes.</p> <div class="credits"> <p class="dwt_author">Chen, Chu-Yung; Frey, Frederick A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">151</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/22621638"> <span id="translatedtitle">Activation analysis of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in opium and cannabis samples</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Rare <span class="hlt">earth</span> concentrations in 65 Opium, Cannabis and Cannabis resin samples seized from various parts of world were determined\\u000a by destructive NAA. Great variations in absolute <span class="hlt">element</span> concentrations, but only small significant differences of rare <span class="hlt">earth</span>\\u000a concentration ratios were found, indicating inconsiderable biogeochemical fractionation. The mean values of these ratios correspond\\u000a with the relative abundances of the rare <span class="hlt">earths</span> in</p> <div class="credits"> <p class="dwt_author">G. Henke; Wilhelms-Universitdt Miinster</p> <p class="dwt_publisher"></p> <p class="publishDate">1977-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">152</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20140003556&hterms=Earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DEarth"> <span id="translatedtitle">Core-Mantle Partitioning of Volatile <span class="hlt">Elements</span> and the Origin of Volatile <span class="hlt">Elements</span> in <span class="hlt">Earth</span> and Moon</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Depletions of volatile siderophile <span class="hlt">elements</span> (VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd) in mantles of <span class="hlt">Earth</span> and Moon, constrain the origin of volatile <span class="hlt">elements</span> in these bodies, and the overall depletion of volatile <span class="hlt">elements</span> in Moon relative to <span class="hlt">Earth</span>. A satisfactory explanation has remained elusive [1,2]. We examine the depletions of VSE in <span class="hlt">Earth</span> and Moon and quantify the amount of depletion due to core formation and volatility of potential building blocks. We calculate the composition of the <span class="hlt">Earth</span>'s PUM during continuous accretion scenarios with constant and variable fO2. Results suggest that the VSE can be explained by a rather simple scenario of continuous accretion leading to a high PT metal-silicate equilibrium scenario that establishes the siderophile <span class="hlt">element</span> content of <span class="hlt">Earth</span>'s PUM near the end of accretion [3]. Core formation models for the Moon explain most VSE, but calculated contents of In, Sn, and Zn (all with Tc < 750 K) are all still too high after core formation, and must therefore require an additional process to explain the depletions in the lunar mantle. We discuss possible processes including magmatic degassing, evaporation, condensation, and vapor-liquid fractionation in the lunar disk.</p> <div class="credits"> <p class="dwt_author">Righter, Kevin; Pando, K.; Danielson, L.; Nickodem, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">153</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005GeCoA..69.1607P"> <span id="translatedtitle">Highly siderophile <span class="hlt">element</span> <span class="hlt">geochemistry</span> of 187Os-enriched 2.8 Ga Kostomuksha komatiites, Baltic Shield</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">New analyses of highly siderophile <span class="hlt">elements</span> (HSE; Re, Os, Ir, Ru, Pt, and Pd) obtained by Carius tube digestion isotope dilution inductively coupled plasma mass-spectrometry (ID-ICPMS) technique are reported for 187Os-enriched 2.8 Ga komatiites from the Kostomuksha greenstone belt. As a result of a significant improvement in the yield over our previous digestions by the NiS fire-assay technique, these komatiites have now been shown to contain 22 to 25% more Os, Ir, and Pt and 34% more Ru. The emplaced komatiite lavas at Kostomuksha thus had siderophile <span class="hlt">element</span> abundances comparable to those of the Abitibi belt. The discrepancies observed between the two techniques are interpreted to be the result of incomplete digestion of HSE carriers (particularly chromite) during the NiS fire-assay procedure. Our results for UB-N peridotite reference material agree well with those obtained by the high-pressure ashing digestion ID-ICPMS technique reported in the literature. Two types of komatiite lavas have been distinguished in this study based on the IPGE (Os, Ir, and Ru) behavior during lava differentiation. The Kostomuksha type is unique and is characterized by an incompatible behavior of IPGEs, with bulk solid-liquid partition coefficients for IPGEs being close to those for olivine. Cumulate zones in this type of komatiite lava occupy <20% of the total thickness of the flows. The Munro type exhibits a compatible behavior of IPGEs during lava differentiation. The cumulate zone in this type of komatiite occupies >20% of the total thickness of the flows. The calculated bulk partition coefficients indicate that, as with the other Munro-type komatiite lavas, the bulk cumulate contained an IPGE-rich minor phase(s) in addition to olivine. The non-CI chondritic HSE pattern for the source of the Kostomuksha komatiites calculated here is similar to that of Abitibi komatiites and to average depleted spinel lherzolite (ADSL) and supports the hypothesis of a non-CI chondritic HSE composition of the <span class="hlt">Earth</span>'s mantle. The absolute HSE abundances in the source of the Kostomuksha komatiite have been demonstrated to be comparable to those of the source of Abitibi komatiites, even though the two komatiites contrast in their Os isotopic compositions. This supports the earlier hypothesis that if core-mantle interaction produced the 187Os/ 188Os radiogenic signature in the Kostomuksha source, it must have occurred in the form of isotope exchange at the core-mantle boundary. Other explanations of the radiogenic Os signature are similarly constrained to conserve the <span class="hlt">elemental</span> abundance pattern in the mantle source of Kostomuksha komatiites.</p> <div class="credits"> <p class="dwt_author">Puchtel, Igor S.; Humayun, Munir</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">154</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40778696"> <span id="translatedtitle">Allanite: thorium and light rare <span class="hlt">earth</span> <span class="hlt">element</span> carrier in subducted crust</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The investigation of deeply subducted eclogites from the Dora-Maira massif, Western Alps reveals that accessory minerals are important hosts for trace <span class="hlt">elements</span>. 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 <span class="hlt">earth</span> <span class="hlt">elements</span> (LREE) and Th and about 75% of U</p> <div class="credits"> <p class="dwt_author">Jörg Hermann</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">155</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/39660188"> <span id="translatedtitle">Distribution of titanium and the rare <span class="hlt">earth</span> <span class="hlt">elements</span> between peridotitic minerals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The concentrations of titanium and rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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 <span class="hlt">elements</span>: HFSE) relative to the REE between clinopyroxenes and orthopyroxenes varies as a function of the whole rock composition and modal mineralogy. The</p> <div class="credits"> <p class="dwt_author">W. F. McDonough; H.-G. Stosch; N. G. Ware</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">156</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24835593"> <span id="translatedtitle">Experimental productivity rate optimization of rare <span class="hlt">earth</span> <span class="hlt">element</span> separation through preparative solid phase extraction chromatography.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Separating individual rare <span class="hlt">earth</span> <span class="hlt">elements</span> from a complex mixture with several <span class="hlt">elements</span> is difficult and this is emphasized for the middle <span class="hlt">elements</span>: Samarium, Europium and Gadolinium. In this study we have accomplished an overloaded one-step separation of these rare <span class="hlt">earth</span> <span class="hlt">elements</span> through preparative ion-exchange high-performance liquid chromatography with an bis (2-ethylhexyl) phosphoric acid impregnated column and nitric acid as eluent. An inductively coupled plasma mass spectrometry unit was used for post column <span class="hlt">element</span> detection. The main focus was to optimize the productivity rate, subject to a yield requirement of 80% and a purity requirement of 99% for each <span class="hlt">element</span>, by varying the flow rate and batch load size. The optimal productivity rate in this study was 1.32kgSamarium/(hmcolumn(3)), 0.38kgEuropium/(hmcolumn(3)) and 0.81kgGadolinium/(hmcolumn(3)). PMID:24835593</p> <div class="credits"> <p class="dwt_author">Knutson, Hans-Kristian; Max-Hansen, Mark; Jönsson, Christian; Borg, Niklas; Nilsson, Bernt</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-06-27</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">157</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFMPP41A2051E"> <span id="translatedtitle">Effects of Drake Passage widening during the Eocene-Oligocene Transition on Southern Ocean bulk sediment trace <span class="hlt">element</span> <span class="hlt">geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Presently, the Southern Ocean provides three-quarters of the global nutrient supply to the low latitude surface ocean (Sarmiento et al. 2004; Palter et al. 2010). In this region the removal of nutrients by sinking organic matter is exceeded by wind-driven upwelling of remineralized nutrients along the Antarctic Circumpolar Current (ACC). The excess nutrients are then advected across the ACC into Subantarctic Mode Water (SAMW), a water mass that transfers the unutilized Southern Ocean nutrients to low-latitude upwelling regions (Toggweiler et al. 1991). However, prior to the opening of the Drake Passage near the Eocene-Oligocene Transition (EOT) the ACC did not exist, suggesting a change in nutrient dynamics of the Southern Ocean. <span class="hlt">Earth</span> system model simulations by Yang et al. 2013 suggest that as the Drake Passage opened, the supply of southern nutrients would have increased, possibly amplifying iron limitation and increasing oxygenation of the deep Southern Ocean. These results indicate that different surface nutrient return pathways in the pre- and post-Drake Passage Southern Ocean may have changed nutrients available to phytoplankton. To assess geological records of these model predictions, Integrated Ocean Drilling Program (IODP) Sites 689 and 1090 have been sampled at 15 to 50 kyr intervals from 31 to 37 Ma. Site 689, located on Maud Rise in the Weddell Sea, and Site 1090, located on Agulhas Ridge in the Southern Atlantic, provide a crucial transect across the Atlantic Sector of the Southern Ocean to examine the influence of the developing ACC on ocean circulation. Bulk sediment trace <span class="hlt">element</span> analyses using inductively coupled plasma optical emission spectrometry (ICP OES) provide indications of biological surface export (Ca, Ba), deep-water oxygenation (U, Mo, Mn), and dust influx (Th, Rb). Results will be presented at the meeting.</p> <div class="credits"> <p class="dwt_author">Elsworth, G.; Galbraith, E. D.; Halverson, G. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">158</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014MinPe.108..419F"> <span id="translatedtitle">Platinum-group <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in western Yangtze Block, SW China: control of platinum-group <span class="hlt">elements</span> by magnetite</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Platinum-group <span class="hlt">element</span> (PGE) <span class="hlt">geochemistry</span> combined with <span class="hlt">elemental</span> <span class="hlt">geochemistry</span> and magnetite compositions are reported for the Mesoproterozoic Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in the western Yangtze Block, SW China. All the Zhuqing gabbros display extremely low concentrations of chalcophile <span class="hlt">elements</span> and PGEs. The oxide-rich gabbros contain relatively higher contents of Cr, Ni, Ir, Ru, Rh, and lower contents of Pt and Pd than the oxide-poor gabbros. The abundances of whole-rock concentrations of Ni, Ir, Ru, and Rh correlate well with V contents in the Zhuqing gabbros, implying that the distributions of these <span class="hlt">elements</span> are controlled by magnetite. The fractionation between Ir-Ru-Rh and Pt-Pd in the Zhuqing gabbros is mainly attributed to fractional crystallization of chromite and magnetite, whereas Ru anomalies are mainly due to variable degrees of compatibility of PGE in magnetite. The order of relative incompatibility of PGEs is calculated to be Pd < Pt < Rh < Ir < Ru. The very low PGE contents and Cu/Zr ratios and high Cu/Pd ratios suggest initially S-saturated magma parents that were highly depleted in PGE, which mainly formed due to low degrees of partial melting leaving sulfides concentrating PGEs behind in the mantle. Moreover, the low MgO, Ni, Ir and Ru contents and high Cu/Ni and Pd/Ir ratios for the gabbros suggest a highly evolved parental magma. Fe-Ti oxides fractionally crystallized from the highly evolved magma and subsequently settled in the lower sections of the magma chamber, where they concentrated and formed Fe-Ti-V oxide ore layers at the base of the lower and upper cycles. Multiple episodes of magma replenishment in the magma chamber may have been involved in the formation of the Zhuqing intrusions.</p> <div class="credits"> <p class="dwt_author">Fan, Hong-Peng; Zhu, Wei-Guang; Zhong, Hong; Bai, Zhong-Jie; He, De-Feng; Ye, Xian-Tao; Chen, Cai-Jie; Cao, Chong-Yong</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">159</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geo.cornell.edu/geology/classes/Chapters/"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> Index</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This site is the index of a book used in a <span class="hlt">geochemistry</span> course taught by W. M. White at Cornell University. There are 15 chapters and a table of contents available. All of the chapters are large PDF files and take some time to download. Figures and exercises accompany the text.</p> <div class="credits"> <p class="dwt_author">William M. White</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">160</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.H21C0837B"> <span id="translatedtitle">Rare <span class="hlt">Earth</span> <span class="hlt">Elemental</span> Signatures in Fungal Fruiting Bodies as Probes into Mineral Breakdown Reactions in Post-glacial Landscapes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The application of rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) abundances in low temperature <span class="hlt">geochemistry</span> and biogeochemistry has improved our understanding of the cycling of various micro- and macronutrients from the bedrock into terrestrial ecosystems. In many continental rocks, REEs are concentrated in accessory phases such as apatite and monazite. These phosphate mineral phases break down readily and may be especially important nutrient sources, particularly for P and Ca, in recently glaciated terrains. Several studies (e.g., 1-3) have suggested that the presence of ectomycorrhizal (ECM) fungi, due to the organic acids they secrete, may play an especially important role in this weathering process. A field-based experiment implementing mesh bags doped with specific mineral compositions confirmed that ECM fungal tissues do record the REE signatures of the minerals they break down (4). In an effort to understand the relative role different ECM fungi may play in mineral breakdown reactions, we have measured REE abundances in tissues of several ECM fruiting bodies. Our preliminary data include Russula, Suillus Americana, Leccinum and Lactarius ECM fungi from three postglacial landscapes. At a given site, the relative abundance of REEs varies between the different ECM fungi. Interestingly, we found distinctions in tissue La/Ce values at two of the sites. Leccinum, a deep rooter, shows much lower La/Ce than the companion Russula and Lactarius samples from the same site. Similarly Suillus tissues demonstrated lower La/Ce when compared to Russula growing nearby. Lower La/Ce is consistent with enhanced dissolution of the mineral apatite, a common accessory phase. While the influence of symbiotic host (beech vs. oak vs. pine) may play some role in the distinctive REE signatures recorded by the fruiting bodies, we attribute the observed differences to organic acid production and tendency to colonize in different horizons of the soil profile. (1) Wallander, Plant and Soil, 2000; (2) Blum et al., Nature, 2002; (3) Hoffland et al., Front Ecol Environ., 2003; (4) Hagerburg et al., Plant and Soil, 2003.</p> <div class="credits"> <p class="dwt_author">Bryce, J. G.; Hobbie, E. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_7");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">161</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/r225122m2483t863.pdf"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> mobility in the Roffna Gneiss, Switzerland</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Roffna Gneiss, a deformed Hercynian granite porphyry within the Penninic nappes of eastern Switzerland, underwent extreme cataclasis with the progressive development of phengite towards the margins of the nappe under conditions of the glaucophane schist to greenschist facies. This resulted in the selective mobilization of major and trace <span class="hlt">elements</span> over distances of 10's to 100's of meters and the</p> <div class="credits"> <p class="dwt_author">Robert D. Vocke; Gilbert N. Hanson; Marc Griinenfelder</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">162</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48722458"> <span id="translatedtitle">The variation of REE (rare <span class="hlt">earth</span> <span class="hlt">elements</span>) patterns in soil-grown plants: a new proxy for the source of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and silicon in plants</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in five species of soil-grown plants (Taxodium japonicum, Populus sieboldii, Sasa nipponica, Thea sinensis and Vicia villosa) and in the soil on which each plant grew were determined with an inductively coupled plasma mass spectrometer (ICP-MS) in order to observe the variation in the distribution of REEs and to elucidate their source in soil-grown plants. The</p> <div class="credits"> <p class="dwt_author">FengFu Fu; Tasuku Akagi; Sadayo Yabuki; Masaya Iwaki</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">163</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JOM...tmp..314K"> <span id="translatedtitle">Addressing Rare-<span class="hlt">Earth</span> <span class="hlt">Element</span> Criticality: An Example from the Aviation Industry</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare-<span class="hlt">earth</span> (RE) <span class="hlt">elements</span> are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-<span class="hlt">earth</span> <span class="hlt">elements</span>, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-<span class="hlt">earth</span> silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-<span class="hlt">earth</span> silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-<span class="hlt">earth</span> cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.</p> <div class="credits"> <p class="dwt_author">Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">164</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JOM....66k2355K"> <span id="translatedtitle">Addressing Rare-<span class="hlt">Earth</span> <span class="hlt">Element</span> Criticality: An Example from the Aviation Industry</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare-<span class="hlt">earth</span> (RE) <span class="hlt">elements</span> are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-<span class="hlt">earth</span> <span class="hlt">elements</span>, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-<span class="hlt">earth</span> silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-<span class="hlt">earth</span> silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-<span class="hlt">earth</span> cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.</p> <div class="credits"> <p class="dwt_author">Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">165</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014GeCoA.128...29H"> <span id="translatedtitle">Preservation of NOM-metal complexes in a modern hyperalkaline stalagmite: Implications for speleothem trace <span class="hlt">element</span> <span class="hlt">geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We report the first quantitative study of the capture of colloidal natural organic matter (NOM) and NOM-complexed trace metals (V, Co, Cu, Ni) in speleothems. This study combines published NOM-metal dripwater speciation measurements with high-resolution laser ablation ICPMS (LA-ICPMS) and sub-annual stable isotope ratio (?18O and ?13C), fluorescence and total organic carbon (TOC) analyses of a fast-growing hyperalkaline stalagmite (pH ˜11) from Poole’s Cavern, Derbyshire UK, which formed between 1997 and 2008 AD. We suggest that the findings reported here elucidate trace <span class="hlt">element</span> variations arising from colloidal transport and calcite precipitation rate changes observed in multiple, natural speleothems deposited at ca. pH 7-8. We find that NOM-metal(aq) complexes on the boundary between colloidal and dissolved (˜1 nm diameter) show an annual cyclicity which is inversely correlated with the alkaline <span class="hlt">earth</span> metals and is explained by calcite precipitation rate changes (as recorded by kinetically-fractionated stable isotopes). This relates to the strength of the NOM-metal complexation reaction, resulting in very strongly bound metals (Co in this system) essentially recording NOM co-precipitation (ternary complexation). More specifically, empirical partition coefficient (Kd) values between surface-reactive metals (V, Co, Cu, Ni) [expressed as ratio of trace <span class="hlt">element</span> to Ca ratios in calcite and in solution] arise from variations in the ‘free’ fraction of total metal in aqueous solution (fm). Hence, differences in the preservation of each metal in calcite can be explained quantitatively by their complexation behaviour with aqueous NOM. Differences between inorganic Kd values and field measurements for metal partitioning into calcite occur where [free metal] ? [total metal] due to complexation reactions between metals and organic ligands (and potentially inorganic colloids). It follows that where fm ? 0, apparent inorganic Kd app values are also ?0, but the true partition coefficient (Kd actual) is significantly higher. Importantly, the Kd of NOM-metal complexes [organic carbon-metal ratio) approaches 1 for the most stable aqueous complexes, as is shown here for Co, but has values of 24-150 for V, Ni and Cu. This implies that ternary surface complexation (metal-ligand co-adsorption) can occur (as for NOM-Co), but is the exception rather than the rule. We also demonstrate the potential for trace metals to record information on NOM composition as expressed through changing NOM-metal complexation patterns in dripwaters. Therefore, a suite of trace metals in stalagmites show variations clearly attributable to changes in organic ligand concentration and composition, and which potentially reflect the state of overlying surface ecosystems. The heterogeneous speciation and size distribution of aqueous NOM and metals (Lead and Wilkinson, 2006; Aiken et al., 2011). The variability in NOM-metal transport in caves that arises from the interaction between infiltration, flow routing, and the hydrodynamic properties of the fine colloids and particulates (Hartland et al., 2012). Variable dissociation kinetics through time as a function of (a) (Hartland et al., 2011). The surface charge of calcite and the availability of CaCO3 lattice sites as well as increased incidence of crystallographic defects with implications for incorporation of a range of trace species (Fairchild and Treble, 2009; Fairchild and Hartland, 2010). Thus, incorporation in speleothem calcite with consistent surface site properties will be determined by: The size and composition (i.e. hydrophilicity/hydrophobicity) of the NOM ligand, affecting adsorption and stability at the calcite surface. The lability (i.e. exchangeability) of the complexed metal and its binding affinity for the calcite surface. The concentration of aqueous complexes. Given the complexities, a partitioning approach to the problem is appropriate as a first approximation rather than a precise description. This study seeks to make the first quantitative connection between the organic and inorgani</p> <div class="credits"> <p class="dwt_author">Hartland, Adam; Fairchild, Ian J.; Müller, Wolfgang; Dominguez-Villar, David</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">166</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AIPC.1362..201S"> <span id="translatedtitle">Development of Electronic Tongue for Detection of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> in Natural Surroundings</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The rare <span class="hlt">earth</span> <span class="hlt">elements</span> (like lanthanum) and other metals like zirconium, arsenic, potassium, copper etc. are some of the <span class="hlt">elements</span>, which are found in the natural surrounding. Since these metals have immense utility in the field of medical science, energy efficient electronic devices, nuclear energy domain, early and easy detection of such metals is very important. In the present work, voltammetric electronic tongue for detection and quantitative determination of these <span class="hlt">elements</span> has been explored. A sensor array comprising of noble metals (like gold, iridium, rhodium etc) has been developed and it exhibits remarkable sensitivity and promising results for detection and analysis of these <span class="hlt">elements</span>.</p> <div class="credits"> <p class="dwt_author">Sarkar, Subrata; Purkait, Monirul; Roy, Jayanta Kumar; Datta, C.; Bhattacharyya, Nabarun; Sarkar, D.; Datta, Jagannath; Chowdhury, D. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">167</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFM.U11A..02T"> <span id="translatedtitle">Imaging <span class="hlt">Earth</span>'s Interior based on Spectral-<span class="hlt">Element</span> and Adjoint Methods (Invited)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We use spectral-<span class="hlt">element</span> and adjoint methods to iteratively improve 3D tomographic images of <span class="hlt">Earth</span>'s interior, ranging from global to continental to exploration scales. The spectral-<span class="hlt">element</span> method, a high-order finite-<span class="hlt">element</span> method with the advantage of a diagonal mass matrix, is used to accurately calculate three-component synthetic seismograms in a complex 3D <span class="hlt">Earth</span> model. An adjoint method is used to numerically compute Frechét derivatives of a misfit function based on the interaction between the wavefield for a reference <span class="hlt">Earth</span> model and a wavefield obtained by using time-reversed differences between data and synthetics at all receivers as simultaneous sources. In combination with gradient-based optimization methods, such as a preconditioned conjugate gradient or L-BSGF method, we are able to iteratively improve 3D images of <span class="hlt">Earth</span>'s interior and gradually minimize discrepancies between observed and simulated seismograms. Various misfit functions may be chosen to quantify these discrepancies, such as cross-correlation traveltime differences, frequency-dependent phase and amplitude anomalies as well as full-waveform differences. Various physical properties of the <span class="hlt">Earth</span> are constrained based on this method, such as elastic wavespeeds, radial anisotropy, shear attenuation and impedance contrasts. We apply this method to study seismic inverse problems at various scales, from global- and continental-scale seismic tomography to exploration-scale full-waveform inversion.</p> <div class="credits"> <p class="dwt_author">Tromp, J.; Zhu, H.; Bozdag, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">168</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/20076087"> <span id="translatedtitle">Radioluminescence and thermoluminescence of rare <span class="hlt">earth</span> <span class="hlt">element</span> and phosphorus-doped zircon</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The radioluminescence and thermoluminescence spectra of synthetic zircon crystals doped with individual trivalent rare <span class="hlt">earth</span> <span class="hlt">element</span> (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-<span class="hlt">earth</span> 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-<span class="hlt">earth</span> lines of the same <span class="hlt">element</span>. 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 <span class="hlt">earth</span> ions. The temperature shifts of the peaks are considerable, up to 200{degree}, and much larger than those cited in other rare-<span class="hlt">earth</span>-doped crystals of LaF{sub 3} and Bi{sub 4}Ge{sub 3}O{sub 12}. The data clearly suggest that the rare-<span class="hlt">earth</span> 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.</p> <div class="credits"> <p class="dwt_author">Karali, T.; Can, N.; Townsend, P.D.; Rowlands, A.P.; Hanchar, J.M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">169</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://hal.archives-ouvertes.fr/docs/00/03/19/34/PDF/Balchit_obsidian_MK.pdf"> <span id="translatedtitle">Geology, volcanology and <span class="hlt">geochemistry</span> Drainage pattern and regional morphostructure at Melka Kunture (Upper Awash, Ethiopia) ........................83</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">) ...........................................93 Guy Kieffer, Jean-Paul Raynal, Guillaume Bardin Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> in Balchit obsidian, volcanology and <span class="hlt">geochemistry</span> Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> in Balchit obsidian (Upper Awash, Ethiopia) Gérard Poupeau1 , Guy Kieffer2 , Jean-Paul Raynal3 , Andy Milton4 , Sarah Delerue1 Obsidian is a large component</p> <div class="credits"> <p class="dwt_author">Paris-Sud XI, Université de</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">170</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/258186"> <span id="translatedtitle">Bulk and surface electronic structure of actinide, rare <span class="hlt">earth</span>, and transition metal <span class="hlt">elements</span> and compounds</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 <span class="hlt">earth</span>, 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 <span class="hlt">earth</span> <span class="hlt">elements</span> 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 <span class="hlt">elements</span>. Theoretical photoemission spectra, including surface effects, were calculated for rare <span class="hlt">earths</span> and actinides.</p> <div class="credits"> <p class="dwt_author">Wills, J.W.; Eriksson, O.</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">171</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40923090"> <span id="translatedtitle">Paleoredox variations in ancient oceans recorded by rare <span class="hlt">earth</span> <span class="hlt">elements</span> in fossil apatite</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> 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</p> <div class="credits"> <p class="dwt_author">Judith Wright; Hans Schrader; William T. Holser</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">172</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5108570"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> variations resulting from inversion of pigeonite and subsolidus reequilibration in lunar ferroan anorthosites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We present results of a secondary ion mass spectrometry study of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in the minerals of two samples of lunar ferroan anorthosite, and the results are applicable to studies of REEs in all igneous rocks, no matter what their planet of origin. Our pyroxene analyses are used to determine solid-solid REE distribution coefficients (D = CREE</p> <div class="credits"> <p class="dwt_author">Odette B. James; Christine Floss; James J. McGee</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">173</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=256482"> <span id="translatedtitle">A LOW-COST RARE <span class="hlt">EARTH</span> <span class="hlt">ELEMENTS</span> RECOVERY TECHNOLOGY - PHASE I</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">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 <span class="hlt">Earth</span> <span class="hlt">Elements</span> (REE) on foreign suppliers and our global competitors. Our innovation...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">174</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://caminos.udc.es/gmni/pdf/1999/1999_cmame.pdf"> <span id="translatedtitle">Preprint of the paper "A Boundary <span class="hlt">Element</span> Numerical Approach for <span class="hlt">Earthing</span> Grid Computation"</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">~na, SPAIN Abstract Analysis and design of substation <span class="hlt">earthing</span> involves computing the equivalent re- sistance in the margin of error [4]. A Boundary <span class="hlt">Element</span> approach for the numerical computation of substation grounding formulation has been implemented in a speci#12;c Computer Aided Design system for grounding analysis developed</p> <div class="credits"> <p class="dwt_author">Colominas, Ignasi</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">175</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=274163"> <span id="translatedtitle">Interactions between exogenous rare <span class="hlt">earth</span> <span class="hlt">elements</span> and phosphorus leaching in packed soil columns</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) increasingly used in agriculture as an amendment for crop growth may help to lessen environmental losses of phosphorus (P) from heavily fertilized soils. The vertical transport characteristics of P and REEs, lanthanum (La), neodymium (Nd), samarium (Sm), and cerium (Ce), w...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">176</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014RJPCA..88.1281L"> <span id="translatedtitle">Studying the volatility of pyrazolone complexes of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> by means of Knudsen effusion</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The temperature dependences of the pressure of saturated vapor of pyrazolone complexes of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> Ln(PMIP)3 (where Ln = Y, Ho, Er, Tm, Lu; PMIP = 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone) are studied via Knudsen effusion, and the enthalpy of their sublimation is determined. Mass spectra and differential scanning calorimetry data are obtained.</p> <div class="credits"> <p class="dwt_author">Lazarev, N. M.; Petrov, B. I.; Bochkarev, L. N.; Safronova, A. V.; Abakumov, G. A.; Arapova, A. V.; Bessonova, Yu. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">177</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ceoas.oregonstate.edu/people/files/mix/Haley_etal_2005_EPSL_REE.pdf"> <span id="translatedtitle">Revisiting the rare <span class="hlt">earth</span> <span class="hlt">elements</span> in foraminiferal tests Brian A. Haley a,*, Gary P. Klinkhammer b</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Revisiting the rare <span class="hlt">earth</span> <span class="hlt">elements</span> in foraminiferal tests Brian A. Haley a,*, Gary P. Klinkhammer b of REEs in planktonic and benthic foraminifera. Several different cleaning protocols were tested. Although, it seems to remobilize metal oxides that are otherwise unaffected in flow-through dissolution</p> <div class="credits"> <p class="dwt_author">Kurapov, Alexander</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">178</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3458658"> <span id="translatedtitle">Undecaprenyl Pyrophosphate Involvement in Susceptibility of Bacillus subtilis to Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The rare <span class="hlt">earth</span> <span class="hlt">element</span> scandium has weak antibacterial potency. We identified a mutation responsible for a scandium-resistant phenotype in Bacillus subtilis. This mutation was found within the uppS gene, which encodes undecaprenyl pyrophosphate synthase, and designated uppS86 (for the Thr-to-Ile amino acid substitution at residue 86 of undecaprenyl pyrophosphate synthase). The uppS86 mutation also gave rise to increased resistance to bacitracin, which prevents cell wall synthesis by inhibiting the dephosphorylation of undecaprenyl pyrophosphate, in addition to enhanced amylase production. Conversely, overexpression of the wild-type uppS gene resulted in increased susceptibilities to both scandium and bacitracin. Moreover, the mutant lacking undecaprenyl pyrophosphate phosphatase (BcrC) showed increased susceptibility to all rare <span class="hlt">earth</span> <span class="hlt">elements</span> tested. These results suggest that the accumulation of undecaprenyl pyrophosphate renders cells more susceptible to rare <span class="hlt">earth</span> <span class="hlt">elements</span>. The availability of undecaprenyl pyrophosphate may be an important determinant for susceptibility to rare <span class="hlt">earth</span> <span class="hlt">elements</span>, such as scandium. PMID:22904278</p> <div class="credits"> <p class="dwt_author">Ochi, Kozo</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">179</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=47189"> <span id="translatedtitle">SEDIMENT REWORKING AND TRANSPORT IN EASTERN LAKE SUPERIOR: IN SITU RARE <span class="hlt">EARTH</span> <span class="hlt">ELEMENT</span> TRACER STUDIES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">A rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) tracer pellet was deployed at the floor of the Ile Parisienne basin of eastern Lake Superior to measure representative sediment reworking and transport processes in the benthic boundary layer of the prnfundal Great Lakes. Samarium oxide, a high neutron-...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">180</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40920258"> <span id="translatedtitle">Fractionation in the solar nebula - Condensation of yttrium and the rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The condensation of Y and the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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</p> <div class="credits"> <p class="dwt_author">W. V. Boynton</p> <p class="dwt_publisher"></p> <p class="publishDate">1975-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_8");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">181</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=234552"> <span id="translatedtitle">Tracing sediment movement on semi-arid watershed using Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> 1988</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">A multi-tracer method employing rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) was used to determine sediment yield and to track sediment movement in a small semiarid watershed. A 0.33 ha watershed near Tombstone, AZ was divided into five morphological units, each tagged with one of five REE oxides. Relative contributi...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">182</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40843195"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in garnets and clinopyroxenes from garnet lherzolite nodules in kimberlites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Six pairs of coexisting garnets and clinopyroxenes were separated from the sheared and granular garnet lherzolite nodules in kimberlites and analyzed for rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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</p> <div class="credits"> <p class="dwt_author">N. Shimizu</p> <p class="dwt_publisher"></p> <p class="publishDate">1975-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">183</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2015RaPC..106..160S"> <span id="translatedtitle">Total photon attenuation coefficients in some rare <span class="hlt">earth</span> <span class="hlt">elements</span> using selective excitation method</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The total mass attenuation coefficients were measured in the <span class="hlt">elements</span> La, Nd, Sm, Gd and Dy belonging to rare <span class="hlt">earth</span> region in the energy range 30-55 keV by employing the selective excitation method. This method facilitates selection of excitation energies near the K edge. The present experimental results were compared with the theoretical values due to Chantler and XCOM.</p> <div class="credits"> <p class="dwt_author">SitaMahalakshmi, N. V.; Kareem, M. A.; Premachand, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">184</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49202245"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of trace <span class="hlt">elements</span> in Chinese coals: A review of abundances, genetic types, impacts on human health, and industrial utilization</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">China will continue to be one of the largest coal producers and users in the world. The high volume of coal use in China has focused attention on the amounts of toxic trace <span class="hlt">elements</span> released from coal combustions and also the valuable trace <span class="hlt">elements</span> extracted or potentially utilized from coal ash.Compared to world coals, Chinese coals have normal background values</p> <div class="credits"> <p class="dwt_author">Shifeng Dai; Deyi Ren; Chen-Lin Chou; Robert B. Finkelman; Vladimir V. Seredin; Yiping Zhou</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">185</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/902964"> <span id="translatedtitle">RARE <span class="hlt">EARTH</span> <span class="hlt">ELEMENTS</span> IN FLY ASHES AS POTENTIAL INDICATORS OF ANTHROPOGENIC SOIL CONTAMINATION</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Studies of rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) content of disposed fly ashes and their potential mobility were neglected for decades because these <span class="hlt">elements</span> were believed to be environmentally benign. A number of recent studies have now shown that REE may pose a long-term risk to the biosphere. Therefore, there is a critical need to study the REE concentrations in fly ash and their potential mobilization and dispersal upon disposal in the environment. We analyzed the REE content of bulk, size fractionated, and density separated fractions of three fly ash samples derived from combustion of sub bituminous coals from the western United States and found that the concentrations of these <span class="hlt">elements</span> in bulk ashes were within the range typical of fly ashes derived from coals from the North American continent. The concentrations of light rare <span class="hlt">earth</span> <span class="hlt">elements</span> (LREE) such as La, Ce, and Nd, however, tended towards the higher end of the concentration range whereas, the concentrations of middle rare <span class="hlt">earth</span> <span class="hlt">elements</span> (MREE) (Sm and Eu) and heavy rare <span class="hlt">earth</span> <span class="hlt">elements</span> (HREE) (Lu) were closer to the lower end of the observed range for North American fly ashes. The concentrations of REE did not show any significant enrichment with decreasing particle size, this is typical of nonvolatile lithophilic <span class="hlt">element</span> behavior during the combustion process. The lithophilic nature of REE was also confirmed by their concentrations in heavy density fractions of these fly ashes being on average about two times more enriched than the concentrations in the light density fractions. Shale normalized average of REE concentrations of fly ashes and coals revealed significant positive anomalies for Eu and Dy. Because of these distinctive positive anomalies of Eu and Dy, we believe that fly ash contamination of soils can be fingerprinted and distinguished from other sources of anthropogenic REE inputs in to the environment.</p> <div class="credits"> <p class="dwt_author">Mattigod, Shas V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">186</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/11378929"> <span id="translatedtitle">Radon (222Rn) level variations on a regional scale: influence of the basement trace <span class="hlt">element</span> (U, Th) <span class="hlt">geochemistry</span> on radon exhalation rates.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The approach proposed in this study provides insight into the influence of the basement <span class="hlt">geochemistry</span> on the spatial distribution of radon (222Rn) levels both at the soil/atmosphere interface and in the atmosphere. We combine different types of in situ radon measurements and a geochemical classification of the lithologies, based on 1/50,000 geological maps, and on their trace <span class="hlt">element</span> (U, Th) contents. The advantages of this approach are validated by a survey of a stable basement area of Hercynian age, located in South Brittany (western France) and characterized by metamorphic rocks and granitoids displaying a wide range of uranium contents. The radon source-term of the lithologies, their uranium content, is most likely to be the primary parameter which controls the radon concentrations in the outdoor environment. Indeed, the highest radon levels (> or = 100 Bq m-3 in the atmosphere, > or = 100 mBq m-2 s-1 at the surface of the soil) are mostly observed on lithologies whose mean uranium content can exceed 8 ppm and which correspond to peraluminous leucogranites or metagranitoids derived from uraniferous granitoids. PMID:11378929</p> <div class="credits"> <p class="dwt_author">Ielsch, G; Thiéblemont, D; Labed, V; Richon, P; Tymen, G; Ferry, C; Robé, M C; Baubron, J C; Béchennec, F</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">187</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013Litho.177..297L"> <span id="translatedtitle">Petrology, major and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>, geochronology, and isotopic composition of granitic intrusions from the vicinity of the Bosumtwi impact crater, Ghana</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Bosumtwi crater is 10.5 km in diameter, 1.07 Ma old, well preserved impact structure located in Ghana (centered at 06°30?N, 01°25?W). It was excavated in rocks of the Early Proterozoic Birimian Supergroup, part of the West African craton. Here, we present a full and detailed characterization of the three granitoid complexes and one mafic dike in the vicinity of the Bosumtwi crater in terms of petrology, major and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>, geochronology, and isotopic composition. This allows us to characterize magmatic evolution of the West African Craton in this area and better understand the geological framework and target rocks of the impact. This study shows that the similar composition (strongly peraluminous muscovite granites and granodiorites) and age (between 2092 ± 6 Ma and 2098 ± 6 Ma) of all granitic intrusions in the proximity of the Bosumtwi crater suggest that they are co-genetic. Granitoids were probably formed as a result of anatexis of TTGs (or rocks derived from them) at relatively low pressure and temperature. We propose that the intrusions from the Bosumtwi area are genetically related to the Banso granite occurring to the east of the crater and can be classified as basin-type, late-stage granitoids. Also a mafic dike located to the NE of the Bosumtwi crater seems to be genetically related to those felsic intrusions. Based on those findings a revised version of the geological map of the Bosumtwi crater area is proposed.</p> <div class="credits"> <p class="dwt_author">Losiak, Anna; Schulz, Toni; Buchwaldt, Robert; Koeberl, Christian</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">188</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21222359"> <span id="translatedtitle">Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the Jurassic coals in the Feke and Kozan (Adana) Areas, Eastern Taurides, Turkey</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">In this study, trace <span class="hlt">element</span> and organic matter-trace <span class="hlt">element</span> relation between Jurassic coals exposed in three different fields in the eastern Taurides were examined and their enrichment values with respect to upper crust values were calculated and the coal characteristics were also compared with world arithmetic means and those from the U.S. In comparison to the Feke and Kizilin coals, Pb, Zn, Ag, and Hg <span class="hlt">element</span> contents of the Gedikli coals are considerably high; Ni, As, and Ge contents are moderately high; and Cr, Cu, Co, Cd, Sb, Ga, and Sn contents are slightly high. The <span class="hlt">element</span> concentrations are very similar to those of other fields. In the Gedikli coals, Sr content is extremely low and Ba content is slightly low with respect to other fields. Re, Mo, U, V, and B <span class="hlt">element</span> concentrations are different for each of three fields. The major <span class="hlt">element</span> contents of the Feke, Gedikli, and Kizilin coals were correlated with world arithmetic means and average values of coals from the U.S. and Fe, K, Mg, and Na concentrations were found to be similar. Ti and Al contents of the world and USA coals are higher while Ca and Mn concentrations are lower. Considering trace <span class="hlt">element</span> contents of the world and U.S. coals, Ba is considerably high, Cu and Zr are moderately high, and Ga, Rb, and Sc <span class="hlt">elements</span> are slightly high. In comparison to world arithmetic means and U.S. coals, Sr content of the Feke and Kizilin coals are very high while those of the Gedikli coals are lower. For major and trace <span class="hlt">elements</span>, factors of enrichment with respect to upper crust values were also calculated. The highest enrichment values were calculated for Ca and S. Except for Se and Rb, all other trace <span class="hlt">elements</span> are enriched with respect to upper crust.</p> <div class="credits"> <p class="dwt_author">Kara-Gulbay, R.; Korkmaz, S. [Karadeniz Technical University, Trabzon (Turkey). Faculty of Engineering</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">189</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1987GeCoA..51..901M"> <span id="translatedtitle">Uranium and rare <span class="hlt">earth</span> <span class="hlt">elements</span> in CO 2-rich waters from Vals-les-Bains (France)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Waters from springs at Vals-les-Bains result from the mixing of a CO 2-rich, highly mineralized water with dilute, shallow subsurface water. Total content of dissolved species vary from 5 mmol/1 to 100 mmol/1. For many <span class="hlt">elements</span>, mixing of these waters is non-linear (non-conservative) and further water-rock reactions take place. The pH is controlled by CO 2 outgassing, redox conditions are controlled by both the iron hydroxide-siderite buffer and the introduction of oxygen with shallow subsurface waters. Among the major <span class="hlt">elements</span>, concentrations of Ca, Mg, Mn, Fe, are related to mixing, CO 2 outgassing and carbonate precipitation. Uranium shows a complex behaviour controlled by carbonate complexing, redox conditions, mixing of waters and leaching from the rocks. The 234U /238U activity ratio is near secular equilibrium. In the more dilute waters, dissolved rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) patterns are almost flat with a slight negative Eu anomaly. In the concentrated waters, heavy rare <span class="hlt">earth</span> <span class="hlt">elements</span> (Gd-Yb, HREE) are strongly enriched relative to light rare <span class="hlt">earth</span> <span class="hlt">elements</span> (Ce-Eu, LREE). We relate the enrichment in HREE to water chemistry and to complexing with carbonate species.</p> <div class="credits"> <p class="dwt_author">Michard, Annie; Beaucaire, Catherine; Michard, Gil</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">190</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/22280491"> <span id="translatedtitle">?-decay of neutron-rich Z?60 nuclei and the origin of rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A large fraction of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these <span class="hlt">elements</span> partially because of nuclear physics uncertainties. To address this problem, a ?-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z?60 that are progenitors of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> with mass number A?460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.</p> <div class="credits"> <p class="dwt_author">Wu, J. [RIKEN Nishina Center, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan and School of Physics and State key Laboratory of Nuclear Physics and Technology, Peking University (China); Nishimura, S.; Lorusso, G.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P. A.; Sakurai, H. [RIKEN Nishina Center, 2-1 Hirosawa, Wako-shi, Saitama 351-0198 (Japan); Xu, Z. Y. [Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033 Tokyo (Japan); Browne, F. [School of Computing Engineering and Mathematics, University of Brighton (United Kingdom); Daido, R.; Fang, Y. F.; Yagi, A.; Nishibata, H.; Odahara, A.; Yamamoto, T. [Department of Physics, Osaka University, Machikaneyama-machi 1-1, Osaka 560-0043 Toyonaka (Japan); Ideguchi, E.; Aoi, N.; Tanaka, M. [Research Center for Nuclear Physics, Osaka University (Japan); Collaboration: EURICA Collaboration; and others</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-02</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">191</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/11545513"> <span id="translatedtitle">Heavy metals and rare <span class="hlt">earth</span> <span class="hlt">elements</span> in phosphate fertilizer components using instrumental neutron activation analysis.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The technique of instrumental neutron activation analysis was applied as a sensitive nondestructive analytical tool for the determination of heavy metals and rare <span class="hlt">earth</span> <span class="hlt">elements</span> in phosphate fertilizer ingredients. The contents of heavy metals Fe, Zn, Co, Cr and Sc as well as rare <span class="hlt">earth</span> <span class="hlt">elements</span> La, Ce, Hf, Eu, Yb and Sm were determined in four samples representing the phosphate fertilizer components (e.g. rock phosphate, limestone and sulfur). These samples were collected from the Abu-Zabal phosphate factory in El-Qalubia governarate, Egypt. The aim of this study was to determine the <span class="hlt">elemental</span> pattern in phosphate ingredients as well as in the produced phosphate fertilizer. Fair agreement was found between the results obtained for the standard reference material Soil-7 and the certified values reported by the International Atomic Energy Agency. The results for the input raw materials (rock phosphate, limestone and sulfur) and the output product as final fertilizer are presented and discussed. PMID:11545513</p> <div class="credits"> <p class="dwt_author">Abdel-Haleem, A S; Sroor, A; El-Bahi, S M; Zohny, E</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">192</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/16379301"> <span id="translatedtitle">[Determination of ten trace rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the sample by atomic emission spectrometry].</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">This paper describes the determination of trace La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Yb and Lu in the sample, using carbon powder, potassium sulfate, barium sulfate, strontium sulfate, and scandium chloride as buffer, by atomic emission spectrometry (AES). Scandium was selected as internal standard line. Sample separation and chemical treatment were not required. The sample was directly loaded into ordinary electrode. The method is simple, rapid and accurate. The determination requirement and influence factors were studied. A new method was developed for the determination of ten rare <span class="hlt">earth</span> <span class="hlt">elements</span>, for which the detection limit is smaller than 0.030%, and the range of the recovery is 94%-105%. The results of these <span class="hlt">elements</span> in standard sample are in agreement with certified values, and the RSD is smaller than 5% (n = 9). The method has been applied to the determination of ten rare <span class="hlt">earth</span> <span class="hlt">elements</span> with satisfactory results. PMID:16379301</p> <div class="credits"> <p class="dwt_author">Li, Hui-zhi; Zhai, Dian-tang; Zhang, Jin; Pei, Mei-shan</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">193</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geotop.ca/pdf/Gestion_Documents/Memoires/Memoire_Emma_Sheard.pdf"> <span id="translatedtitle">Behaviour of zirconium, niobium, yttrium and the rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Thor Lake rare-metal</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Behaviour of zirconium, niobium, yttrium and the rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Thor Lake rare-metal © Emma Rebecca Sheard, 2010 #12;i ABSTRACT The Thor Lake rare-metal (Zr, Nb, Y, REE, Ta, Be, Ga) deposit and the heavy rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the world. Much of the potentially economic mineralization was concentrated</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">194</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://hal.archives-ouvertes.fr/docs/00/45/06/82/PDF/HAL_Janvier_2009_Rare_Earth_Element_sorption_by_basaltic_rock.pdf"> <span id="translatedtitle">Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> sorption by basaltic rock: experimental data and modeling results using the "Generalised Composite approach".</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> sorption by basaltic rock: experimental data and modeling results using Email address : emmanuel.tertre@univ-poitiers.fr Keywords: sorption, lanthanides, basalt, surface.1016/j.gca.2007.12.015 #12;Abstract Sorption of the 14 Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> (REE) by basaltic rock</p> <div class="credits"> <p class="dwt_author">Paris-Sud XI, Université de</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">195</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40778552"> <span id="translatedtitle">Zircon trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>: partitioning with garnet and the link between U–Pb ages and metamorphism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">With the aim to link zircon composition with paragenesis and thus metamorphic conditions, zircons from eclogite- and granulite-facies rocks were analysed for trace <span class="hlt">elements</span> using LA-ICP-MS and SHRIMP ion microprobe. Metamorphic zircons from these different settings display a large variation in trace <span class="hlt">element</span> composition. In the granulites, zircon overgrowths formed in equilibrium with partial melt and are similar to magmatic</p> <div class="credits"> <p class="dwt_author">Daniela Rubatto</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">196</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011GeCoA..75.6374F"> <span id="translatedtitle">Improved provenance tracing of Asian dust sources using rare <span class="hlt">earth</span> <span class="hlt">elements</span> and selected trace <span class="hlt">elements</span> for palaeomonsoon studies on the eastern Tibetan Plateau</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Asian Monsoon forms an important part of the <span class="hlt">earth</span>'s climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace <span class="hlt">elemental</span> (Sc, Y, Th and the rare <span class="hlt">earth</span> <span class="hlt">elements</span>) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai-Tibetan Plateau) dust sources. Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle REE relative to the upper continental crust and average shale but the Thar desert has a REE signature distinctly different from all other dust sources. There are significant differences in major, trace and REE compositions between the coarse and fine fractions of the surface sands, with the finest <4 ?m fraction enriched in Al 2O 3, Fe 2O 3, MnO, MgO and K 2O and the <32 ?m fractions in Sc, Y, Th and the REE relative to the coarse fractions. The <4 ?m fraction best represents the bulk REE <span class="hlt">geochemistry</span> of the samples. The provenance tracers Y/?REE, La/Er, La/Gd, Gd/Er, La/Yb, Y/Tb, Y/La, Y/Nd and to a certain extent the europium anomaly Eu/Eu ? (all REE normalized to post-Archean Australian shale, PAAS) are particle size-independent tracers, of which combinations of Y/?REE, La/Yb, Y/Tb, Y/La and Eu/Eu ? can be used to distinguish the Thar desert, the Chinese deserts, the Chinese loess plateau and the Tibetan soils. Their independence upon grain size means that these tracers can be applied to the long-range provenance tracing of Asian dust even when only bulk samples are available in the source region. Combinations of La/Th, Y/Tb, Y/?REE, Sc/La and Y/Er distinguish the Tibetan soils from the Chinese loess plateau and the Chinese deserts. La/Th and notably Th/?REE isolate the signature of the Badain Juran desert and the combination of Sc/La and Y/Er that of the Taklamakan desert. The similarity in all trace and REE-based provenance tracers between the northern Qaidam basin and Tengger desert suggests that these two deposits may have a common aeolian source.</p> <div class="credits"> <p class="dwt_author">Ferrat, Marion; Weiss, Dominik J.; Strekopytov, Stanislav; Dong, Shuofei; Chen, Hongyun; Najorka, Jens; Sun, Youbin; Gupta, Sanjeev; Tada, Ryuji; Sinha, Rajiv</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">197</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014NatSR...4E6221Z"> <span id="translatedtitle">The Environmental <span class="hlt">Geochemistry</span> of Trace <span class="hlt">Elements</span> and Naturally Radionuclides in a Coal Gangue Brick-Making Plant</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">An investigation focused on the transformation and distribution behaviors of trace <span class="hlt">elements</span> and natural radionuclides around a coal gangue brick plant was conducted. Simultaneous sampling of coal gangue, brick, fly ash and flue gas were implemented. Soil, soybean and earthworm samples around the brick plant were also collected for comprehensive ecological assessment. During the firing process, trace <span class="hlt">elements</span> were released and redistributed in the brick, fly ash and the flue gas. <span class="hlt">Elements</span> can be divided into two groups according to their releasing characteristics, high volatile <span class="hlt">elements</span> (release ratio higher than 30%) are represented by Cd, Cu, Hg, Pb, Se and Sn, which emitted mainly in flue gas that would travel and deposit at the northeast and southwest direction around the brick plant. Cadmium, Ni and Pb are bio-accumulated in the soybean grown on the study area, which indicates potential health impacts in case of human consumption. The high activity of natural radionuclides in the atmosphere around the plant as well as in the made-up bricks will increase the health risk of respiratory system.</p> <div class="credits"> <p class="dwt_author">Zhou, Chuncai; Liu, Guijian; Cheng, Siwei; Fang, Ting; Lam, Paul K. S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">198</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40884555"> <span id="translatedtitle">High contents of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in stream waters of a Cu–Pb–Zn mining area</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Stream waters draining an old mining area present very high rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) contents, reaching 928 ?g\\/l as the maximum total value (?REE). The middle rare <span class="hlt">earth</span> <span class="hlt">elements</span> (MREEs) are usually enriched with respect to both the light (LREEs) and heavy (HREEs) <span class="hlt">elements</span> of this group, producing a characteristic “roof-shaped” pattern of the shale Post-Archean Australian Shales-normalized concentrations. At</p> <div class="credits"> <p class="dwt_author">G Protano; F Riccobono</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">199</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/(ISSN)1525-2027/"> <span id="translatedtitle">G3 (<span class="hlt">Geochemistry</span>, Geophysics, Geosystems)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">_G3 (<span class="hlt">Geochemistry</span>, Geophysics, Geosystems)_ is a forthcoming electronic journal that will be issued by the Geochemical Society and the American Geophysical Union (AGU). This journal publishes "relevant observational, experimental, and theoretical investigations of the solid <span class="hlt">Earth</span>, hydrosphere, atmosphere, and biosphere that pertain to understanding the <span class="hlt">Earth</span> as a system." Scientists interested in contributing to this journal must submit material electronically via a Web form. Although a starting date of publication has not been mentioned at the Website, email announcements will be sent to subscribers (subscription is free) once the journal begins publication.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">200</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1990Litho..25..219S"> <span id="translatedtitle">Behaviour of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> during high-pressure metamorphism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The behaviour of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REE) during high-pressure metamorphism has been studied to estimate their possible use in determining the geodynamic settings of eclogite procoliths. Eclogites exhibiting various degrees of amphibolitization have been studied in a number lf metamorphic complexes in the Urals-Mongolian fold belt (the Kokchetav massif in northern Kazakhstan and the Atbashi range in the Central Tien-Shan, all in the U.S.S.R.). In addition, an eclogitized metagabbro from the Koralpe, Austrian Alps and gabbroids transformed into garnet amphibolites from the Kokhchetav massif have been investigated. The analytical data suggest that about 30-60% of the light rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (LREE) in eclogites is present in the intergranular space. The results of the investigation demonstrate that the REE were virtually immobile during eclogite formation. Their low mobility can be explained either by absence of complex formers in the fluid phase or by low fluid/rock ratio.</p> <div class="credits"> <p class="dwt_author">Shatsky, V. S.; Kozmenko, O. A.; Sobolev, N. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-11-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_9");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_12");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">201</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21541284"> <span id="translatedtitle">Symmetric charge-transfer cross sections of IIIa rare-<span class="hlt">earth</span>-metal <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Symmetric charge-transfer cross sections of IIIa rare-<span class="hlt">earth</span>-metal <span class="hlt">elements</span> (Sc, Y, and Gd) in the impact energy range of 30 to 1000 eV were measured for the first time. The experiments were performed with a crossed-beam apparatus that featured primary ion production by photoionization with a tunable dye laser. Comparing the cross sections of IIIa rare-<span class="hlt">earth</span>-metal <span class="hlt">elements</span> ({sigma}{sub Sc}, {sigma}{sub Y}, and {sigma}{sub Gd}) with those of alkali metals or helium {sigma}{sub 0}, we found that {sigma}{sub 0{approx_equal}{sigma}Sc}<{sigma}{sub Y}<{sigma}{sub Gd{approx_equal}}2{sigma}{sub 0}at an impact energy of 1000 eV.</p> <div class="credits"> <p class="dwt_author">Hashida, Masaki; Sakabe, Shuji; Izawa, Yasukazu [ARCBS, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan) and Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502 (Japan); Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan) and Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-03-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">202</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5209123"> <span id="translatedtitle">Reconciling the <span class="hlt">elemental</span> and Sr isotope composition of Himalayan weathering fluxes: insights from the carbonate <span class="hlt">geochemistry</span> of stream waters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Determining the relative proportions of silicate vs. carbonate weathering in the Himalaya is important for understanding atmospheric CO2 consumption rates and the temporal evolution of seawater Sr. However, recent studies have shown that major <span class="hlt">element</span> mass-balance equations attribute less CO2 consumption to silicate weathering than methods utilizing Ca\\/Sr and 87Sr\\/86Sr mixing equations. To investigate this problem, we compiled literature data</p> <div class="credits"> <p class="dwt_author">ANDREW D. JACOBSON; J OEL D. BLUM; LYNN M. WALTER</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">203</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17837193"> <span id="translatedtitle">Bishop tuff revisited: new rare <span class="hlt">Earth</span> <span class="hlt">element</span> data consistent with crystal fractionation.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The Bishop Tuff of eastern California is the type example of a high-silica rhyolite that, according to Hildreth, supposedly evolved by liquid-state differentiation. New analyses establish that the Bishop Tuff "earlyllate" rare <span class="hlt">earth</span> <span class="hlt">element</span> trend reported by Hildreth mimics the relations between groundmass glasses and whole rocks for allanite-bearing pumice. Differences in <span class="hlt">elemental</span> concentrations between whole rock and groundmass are the result of phenocryst precipitation; thus the data of Hildreth are precisely those expected to result from crystal fractionation. PMID:17837193</p> <div class="credits"> <p class="dwt_author">Cameron, K L</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-06-22</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">204</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56432108"> <span id="translatedtitle">Surface Ionization of Some Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> on Hot Polycrystalline Tungsten Surface</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The surface ionization of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> Gd, Ho, Dy, Pr and Er has been studied for very low electric field (<3 KV\\/cm) at the surface and the ionization potentials (I.P.) of these <span class="hlt">elements</span> have been measured. The values of ionization potentials are: Gd- 6.73± 0.09 eV, Ho- 6.08± 0.09 eV, Dy- 5.72± 0.10 eV, Pr- 5.61± 0.11 eV</p> <div class="credits"> <p class="dwt_author">S. D. Dey; S. B. Karmohapatro</p> <p class="dwt_publisher"></p> <p class="publishDate">1967-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">205</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40778503"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in waters from the albitite-bearing granodiorites of Central Sardinia, Italy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">With the aim of contributing to the knowledge of the geochemical behaviour and mobility of the rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) in the natural water systems, the ground and surface waters of the Ottana–Orani area (Central Sardinia, Italy) were sampled. The study area consists of albititic bodies included in Hercynian granodiorites. The waters have pH in the range of 6.0–8.6, total</p> <div class="credits"> <p class="dwt_author">Riccardo Biddau; Rosa Cidu; Franco Frau</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">206</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/39665146"> <span id="translatedtitle">A rare <span class="hlt">earth</span> <span class="hlt">element</span>-rich carbonatite dyke at Bayan Obo, Inner Mongolia, North China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Summary  ¶A carbonatite dyke, extremely enriched in rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE), is reported from Bayan Obo, Inner Mongolia, North China.\\u000a The REE content in the dyke varies from 1?wt% to up to 20?wt%. The light REEs are enriched and highly fractionated relative\\u000a to the heavy REEs, and there is no Eu anomaly. Although carbon isotope ?13C (PDB) values of the carbonatites</p> <div class="credits"> <p class="dwt_author">X.-M. Yang; X.-Y. Yang; Y.-F. Zheng; M. J. Le Bas</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">207</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41032820"> <span id="translatedtitle">Fracture toughness improvement of austempered high silicon steel by titanium, vanadium and rare <span class="hlt">earth</span> <span class="hlt">elements</span> modification</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The microstructure of austempered high silicon (AHS) steel before and after treating with a modifier containing titanium, vanadium and rare <span class="hlt">earth</span> <span class="hlt">elements</span> (so-called Ti–V–RE modifier) and austempered at different temperatures has been investigated. The plane strain fracture toughness of the steel in room temperature and ambient atmosphere has been examined. The microstructure was characterized using X-ray diffraction, scanning electron microscopy,</p> <div class="credits"> <p class="dwt_author">Xiang Chen; Yanxiang Li</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">208</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40925963"> <span id="translatedtitle">Ocean particle chemistry: The fractionation of rare <span class="hlt">earth</span> <span class="hlt">elements</span> between suspended particles and seawater</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">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 <span class="hlt">earth</span> <span class="hlt">element</span> (REE) composition of the surface coatings, in marked contrast to the crust-like REE composition of</p> <div class="credits"> <p class="dwt_author">E. R. Sholkovitz; W. M. Landing; B. L. Lewis</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">209</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5847041"> <span id="translatedtitle">Distribution of alkaline <span class="hlt">earth</span> <span class="hlt">elements</span> between aqueous solutions and polymeric sorbent impregnated with 8-hydroxyquinoline</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The interphase distribution of microimpurities of alkaline <span class="hlt">earth</span> <span class="hlt">elements</span> (AEE) between solutions of alkali metal chlorides and a macroporous styrene-divinyl-benzene copolymer impregnated with 8-hydroxyquinoline was studied. The influence of the phase composition on the distribution coefficients of AEE and 8-hydroxyquinoline was examined. The advantages of sorption of the impurities by an impregnated sorbent over liquid extraction for thorough purification of salt solutions were shown.</p> <div class="credits"> <p class="dwt_author">Turanov, A.N.; Kremenskaya, I.N.; Putrya, L.V.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">210</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40207082"> <span id="translatedtitle">Heavy metals and rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in soil from the Nam Co Basin, Tibetan Plateau</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">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 <span class="hlt">earth</span> <span class="hlt">elements</span> (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</p> <div class="credits"> <p class="dwt_author">Chaoliu Li; Shichang Kang; Xiaoping Wang; F. Ajmone-Marsan; Qianggong Zhang</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">211</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JAESc..43..150K"> <span id="translatedtitle">Petrology and <span class="hlt">geochemistry</span> of prograde deserpentinized peridotites from Happo-O'ne, Japan: Evidence of <span class="hlt">element</span> mobility during deserpentinization</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The prograde deserpentinized peridotites from the talc zone in the Happo-O'ne complex, central Japan, show differences in their field relation and mineral assemblage with the high-P retrograde peridotites of the other part of the complex. They show a mineral assemblage, olivine + talc + antigorite ± prograde tremolite ± chlorite, formed by thermal metamorphism around the granitic intrusion at T, 500-650 °C and P < 7 kbar. The olivine has numerous opaque inclusions and high Fo (91.5-96.5) relative to the retrograde olivine, reflecting its formation by deserpentinization. The prograde tremolite, which is low in Al 2O 3 (<1.0 wt.%), Cr 2O 3 (<0.35 wt.%), and Na 2O (<0.6 wt.%) but high in Mg# (up to 0.98) and SiO 2 (up to 59.9 wt.%), is different in size, shape and chemistry from the retrograde tremolite. The prograde peridotites display a U-shaped REE pattern (0.02-0.5 times PM), similar to diopside-zone retrograde metaperidotites, possible protoliths. They are enriched in LILE (e.g., Cs, Pb, Sr, Rb) relative to HFSE (e.g., Ta, Hf, Zr, Nb), like their protoliths, because of their local re-equilibration with the fluid released during dehydration of the protoliths. They have high contents of REE and some trace <span class="hlt">elements</span> (e.g., Cs, Th, U, Ta) relative to their protoliths because of an external-<span class="hlt">element</span> addition from the granitic magma. In-situ analyses of peridotitic silicates confirmed that the prograde tremolite and talc display a spoon-shaped primitive mantle (PM)-normalized REE pattern (0.1-3 times PM) in which LREE are higher than HREE contents. The prograde tremolite is depleted in Al, Na, Cr, Sc, V, Ti, B, HREE and Li, but is enriched in Si, Cs, U, Th, HFSE (Hf, Zr, Nb, Ta), Rb and Ba relative to the retrograde tremolite; the immobile-<span class="hlt">element</span> depletion in this tremolite is inherited from its source (antigorite + secondary diopside), whereas the depletion of mobile <span class="hlt">elements</span> (e.g., Li, B, Na, Al) is ascribed to their mobility during the deserpentinization and/or the depleted character of the source of tremolite. The enrichment of HFSE and LILE in the prograde tremolite is related to an external addition of these <span class="hlt">elements</span> from fluid/melt of the surrounding granitic magma and/or in situ equilibrium with LILE-bearing fluid released during dehydration of serpentinized retrograde metaperidotites and olivine-bearing serpentinites (protoliths). The prograde olivine is higher in REE and most trace-<span class="hlt">element</span> contents than the retrograde one due to the external addition of these <span class="hlt">elements</span>; it is enriched in B, Co and Ni, but depleted in Li that was liberated during deserpentinization by prograde metamorphism.</p> <div class="credits"> <p class="dwt_author">Khedr, Mohamed Zaki; Arai, Shoji</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">212</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/11529577"> <span id="translatedtitle">Transport of rare <span class="hlt">earth</span> <span class="hlt">element</span>-tagged soil particles in response to thunderstorm runoff.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The downslope transport of rare <span class="hlt">earth</span> <span class="hlt">element</span>-tagged soil particles remobilized during a spring thunderstorm was studied on both a natural prairie and an agricultural field in southwestern Iowa (U.S.A.). A technique was developed for tagging natural soils with the rare <span class="hlt">earth</span> <span class="hlt">elements</span> Eu, Tb, and Ho to approximately 1,000 ppm via coprecipitation with MnO2. Tagged material was replaced in target locations; surficial soil samples were collected following precipitation and runoff; and rare <span class="hlt">earth</span> <span class="hlt">element</span> concentrations were determined by inductively coupled plasma mass spectrometry. Diffusion and exponential models were applied to the concentration-distance data to determine particle transport distances. The results indicate that the concentration-distance data are well described by the diffusion model, butthe exponential model does not simulate the rapid drop-off in concentrations near the tagged source. Using the diffusion model, calculated particle transport distances at all hillside locations and at both the cultivated and natural prairie sites were short, ranging from 3 to 73 cm during this single runoff event. This study successfully demonstrates a new tool for studying soil erosion. PMID:11529577</p> <div class="credits"> <p class="dwt_author">Matisoff, G; Ketterer, M E; Wilson, C G; Layman, R; Whiting, P J</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-08-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">213</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22304002"> <span id="translatedtitle">Evaluating rare <span class="hlt">earth</span> <span class="hlt">element</span> availability: a case with revolutionary demand from clean technologies.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The future availability of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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 <span class="hlt">earth</span> markets and market behavior. Increased use of wind energy and electric vehicles are key <span class="hlt">elements</span> 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-<span class="hlt">earth</span> magnets, future adoption of these technologies may result in large and disproportionate increases in the demand for these two <span class="hlt">elements</span>. 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</p> <div class="credits"> <p class="dwt_author">Alonso, Elisa; Sherman, Andrew M; Wallington, Timothy J; Everson, Mark P; Field, Frank R; Roth, Richard; Kirchain, Randolph E</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-03-20</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">214</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2584670"> <span id="translatedtitle">Toward understanding early <span class="hlt">Earth</span> evolution: Prescription for approach from terrestrial noble gas and light <span class="hlt">element</span> records in lunar soils</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Because of the almost total lack of geological record on the <span class="hlt">Earth</span>'s surface before 4 billion years ago, the history of the <span class="hlt">Earth</span> 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 <span class="hlt">elements</span> such as He, N, O, Ne, and Ar would shed a new light on this dark age in the <span class="hlt">Earth</span>'s history and resolve three of the most fundamental questions in <span class="hlt">earth</span> science: the onset time of the geomagnetic field, the appearance of an oxygen atmosphere, and the secular variation of an <span class="hlt">Earth</span>–Moon dynamical system. PMID:19001263</p> <div class="credits"> <p class="dwt_author">Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A.; Miura, Yayoi N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">215</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70022811"> <span id="translatedtitle">Major, trace <span class="hlt">element</span> and isotope <span class="hlt">geochemistry</span> (Sr-Nd-Pb) of interplinian magmas from Mt. Somma-Vesuvius (Southern Italy)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Major, trace <span class="hlt">element</span> and isotopic (Sr, Nd, Pb) data are reported for representative samples of interplinian (Protohistoric, Ancient Historic and Medieval Formations) activity of Mt. Somma-Vesuvius volcano during the last 3500 years. Tephra and lavas exhibit significant major, trace <span class="hlt">element</span> and isotopic variations. Integration of these data with those obtained by previous studies on the older Somma suites and on the latest activity, allows to better trace a complete petrological and geochemical evolution of the Mt. Somma-Vesuvius magmatism. Three main groups of rocks are recognized. A first group is older than 12.000 yrs, and includes effusive-explosive activity of Mt. Somma. The second group (8000-2700 yrs B.P.) includes the products emitted by the Ottaviano (8000 yrs. B.P.) and Avellino (3550 yrs B.P.) plinian eruptions and the interplinian activity associated with the Protohistoric Formation. Ancient Historic Formation (79-472 A.D.), Medieval Formation (472-1139 A.D.) and Recent interplinian activity (1631-1944 A.D.) belong to the third group of activity (79-1944 A.D.). The three groups of rocks display distinct positive trends of alkalis vs. silica, which become increasingly steeper with age. In the first group there is an increase in silica and alkalis with time, whereas an opposite tendency is observed in the two younger groups. Systematic variations are also evident among the incompatible (Pb, Zr, Hf, Ta, Th, U, Nb, Rb, Cs, Ba) and compatible <span class="hlt">elements</span> (Sr, Co, Cr). REE document variable degrees of fractionation, with recent activity displaying higher La/Yb ratios than Medieval and Ancient Historic products with the same degree of evolution. N-MORB normalized multi-<span class="hlt">element</span> diagrams for interplinian rocks show enrichment in Rb, Th, Nb, Zr and Sm (> *10 N-MORB). Sr isotope ratios are variable, with Protohistoric rocks displaying 87Sr/86Sr= 0.70711-0.70810, Ancient Historic 87Sr/86Sr=0.70665-0.70729, and Medieval 87Sr/86Sr=0.70685-0.70803. Neodymium isotopic compositions in the interplinian rocks show a tendency to become slightly more radiogenic with age, from the Protohistoric (143Nd/144Nd=0.51240-0.51247) to Ancient Historic (143Nd/144Nd=0.51245-0.51251). Medieval interplinian activity (143Nd/144Nd: 0.51250-0.51241) lacks meaningful internal trends. All the interplinian rocks have virtually homogeneous compositions of 207Pb/204Pb and 208Pb/204Pb in acid-leached residues (207Pb/204Pb ???15.633 to 15.687, 208Pb/204Pb ???38.947 to 39.181). Values of 206Pb/204Pb are very distinctive, however, and discriminate among the three interplinian cycles of activity (Protohistoric: 18.929-18.971, Ancient Historic: 19.018-19.088, Medieval: 18.964-19.053). Compositional trends of major, trace <span class="hlt">element</span> and isotopic compositions clearly demonstrate strong temporal variations of the magma types feeding the Somma-Vesuvius activity. These different trends are unlikely to be related only to low pressure evolutionary processes, and reveal variations of parental melt composition. Geochemical data suggest a three component mixing scheme for the interplinian activity. These involve HIMU-type and DMM-type mantle and Calabrian-type lower crust. Interaction between these components has taken place in the source; however, additional quantitative constraints must be acquired in order to better discriminate between magma characteristics inherited from the sources and those acquired during shallow level evolution.</p> <div class="credits"> <p class="dwt_author">Somma, R.; Ayuso, R.A.; de Vivo, B.; Rolandi, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">216</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JAESc..95..228C"> <span id="translatedtitle">Petrogenesis of Late Permian sodic metagranitoids in southeastern Korea: SHRIMP zircon geochronology and <span class="hlt">elemental</span> and Nd-Hf isotope <span class="hlt">geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">One of the striking tectonomagmatic features recently found in southeastern Korea is the occurrence of ca. 250 Ma high-silica adakite. Sodic metagranitoids mainly consisting of tonalitic-trondhjemitic-granodioritic gneisses occur in the Andong-Cheongsong area adjacent to the Yeongdeok adakite site. To investigate temporal and petrogenetic relationships of these orthogneisses with the adakite, we conducted SHRIMP zircon U-Pb dating as well as <span class="hlt">elemental</span> and Nd-Hf isotopic analyses. Zircon core ages of the orthogneisses (ca. 262-251 Ma) confirm the widespread occurrence of arc-related Late Permian magmatism in southeastern Korea. The Late Triassic (ca. 230 Ma) zircon overgrowths reflect a thermal overprint probably related to the initiation of another subduction system. The analyzed orthogneisses have major <span class="hlt">element</span> compositions comparable to the Phanerozoic adakites and Archean TTG suite, such as high SiO2 (58.7-65.5 wt.%) and Al2O3 (17.1-19.1 wt.%) contents and Na2O/K2O ratios (1.83-4.95). However, their moderate Sr/Y (35-43) and La/Yb (14-53) ratios and negative Eu anomalies (Eu/Eu* = 0.75-0.95) are incompatible with the key features reported from the Yeongdeok adakite. Moreover, initial whole-rock ?Nd (-7.9 to -3.3) and zircon ?Hf (-0.3 ± 2.4) values of the orthogneisses negate a direct derivation from the subducted slab. Our <span class="hlt">elemental</span> and Nd-Hf isotopic data collectively suggest that the protoliths of the tonalitic-trondhjemitic-granodioritic gneisses were generated by partial melting of mafic lower crust at depths shallower than the garnet stability field. Our Nd and Hf model ages of the gneisses, together with those previously reported from the Mesozoic granitoids indicate a selective involvement of young source materials along the margin of the Yeongnam massif. The Hf isotopic compositions of zircons from a trondhjemitic gneiss attest to the involvement of primitive melts during their crystallization. The ridge subduction and consequent development of a slab window may have facilitated partial melting of the subducted oceanic lithosphere and the lower crust.</p> <div class="credits"> <p class="dwt_author">Cheong, Chang-sik; Kim, Namhoon; Kim, Jeongmin; Yi, Keewook; Jeong, Youn-Joong; Park, Chan-Soo; Li, Huai-kun; Cho, Moonsup</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">217</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1994JVGR...62..429N"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of the 1989 1990 eruption of redoubt volcano: Part I. Whole-rock major- and trace-<span class="hlt">element</span> chemistry</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The 1989-1990 eruption of Redoubt Volcano produced medium-K calc-alkaline andesite and dacite of limited compositional range (58.2-63.4% SiO 2) and entrained quenched andesitic inclusions (55% SiO 2) which bear chemical similarities to the rest of the ejecta. The earliest (December 15) magmas are pumiceous, often compositionally banded, and the majority is relatively mafic (< 59% SiO 2). The most silicic magmas of the eruption are the late December to early January domes (up to 63.4% SiO 2). Subsequent magmas formed domes and rare pumices which converge on 60% SiO 2. Chemical variations among ejecta comprise tight, linear, two-component arrays for all <span class="hlt">elements</span> for which the analytical uncertainty is much less than the compositional range. The two-component arrays are interpreted as mixing arrays between unrelated magmas because several of the arrays are at steep angles to the normal liquid line of descent. Additionally, the felsic endmember cannot be easily related to the mafic endmember by normal high-temperature igneous processes (e.g., the silicic endmember has higher Zr yet lower Hf than the mafic endmember). Also relative enrichments of highly incompatible <span class="hlt">elements</span> are dramatically different across the arrays. The mixing event must have preceded eruption by a significant, yet unspecified amount of time because groundmass glass compositions are homogeneous for all post-December samples (Swanson et al., 1994-this volume), in spite of the whole-rock chemical diversity. This implies time for additional crystallization after the mixing event. Swanson et al. (1994-this volume) discuss evidence for a potentially different mixing event recorded only in December 15 magmas. Cognate cumulate xenoliths composed of pl+cpx+opx+hb+mt+melt were recovered from January and April deposits. These blocks differ from local batholithic country rock in their low concentrations of incompatible <span class="hlt">elements</span> (e.g., Rb < 5 ppm vs 20-90 ppm, Ba < 150 ppm vs 300-2000 ppm) and low SiO 2 (< 50 wt.% vs > 60 wt.%). They have Mg, Cr, Ni, Sc, and V contents higher than the andesites, but lower than Redoubt basalts and basaltic andesites. Thus, they may be crystallization products of andesites, but do not represent the cumulate residue of basalt fractionation. The xenoliths were probably derived from a shallow or intermediate crustal chamber.</p> <div class="credits"> <p class="dwt_author">Nye, Christopher J.; Swanson, Samuel E.; Avery, Victoria F.; Miller, Thomas P.</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">218</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23896401"> <span id="translatedtitle">Major and minor <span class="hlt">element</span> <span class="hlt">geochemistry</span> of deep-sea sediments in the Azores Platform and southern seamount region.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The Azores Platform and the Irving and Great Meteor seamounts south of the archipelago (38°N-29°N) have rarely been studied geochemically, a fact which is surprising given that they represent the south-eastern limit of region V outlined in the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR Convention). The main aim of the present work was therefore to characterise the spatial variability of major and minor <span class="hlt">elements</span> in deep-sea sediment cores from these two regions. XRD and geochemical analyses revealed that whereas the Azores Platform sediments are composed of a mixture of biogenic and detrital volcanic material, those at the seamounts are characterised by carbonated biogenic remains. The latter sediments were found to contain very low amounts of volcanic or hydrothermal detrital material, being almost entirely comprised of CaCO3 (more than 80%). PMID:23896401</p> <div class="credits"> <p class="dwt_author">Palma, Carla; Oliveira, Anabela; Valença, Manuela; Cascalho, João; Pereira, Eduarda; Lillebø, Ana I; Duarte, Armando C; Pinto de Abreu, Manuel</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-10-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">219</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19820048232&hterms=rare+earths+gd&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drare%2Bearths%2Bgd"> <span id="translatedtitle">Complementary rare <span class="hlt">earth</span> <span class="hlt">element</span> patterns in unique achondrites, such as ALHA 77005 and shergottites, and in the <span class="hlt">earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Abundances of major, minor, and trace <span class="hlt">elements</span> are determined in the Antarctic achondrite Allan Hills (ALHA) 77005 via sequential instrumental and radiochemical neutron activation analysis. The rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) abundances of ALHA 77005 reveal a unique chondritic normalized pattern; that is, the REEs are nearly unfractionated from La to Pr at approximately 1.0X chondrites, monotonically increased from Pr to Gd at approximately 3.4X with no Eu anomaly, nearly unfractionated from Gd and Ho and monotonically decreased from Ho to Lu at approximately 2.2X. It is noted that this unique REE pattern of ALHA 77005 can be modeled by a melting process involving a continuous melting and progressive partial removal of melt from a light REE enriched source material. In a model of this type, ALHA 77005 could represent either a crystallized cumulate from such a melt or the residual source material. Calculations show that the parent liquids for the shergottites could also be derived from a light REE enriched source material similar to that for ALHA 77005.</p> <div class="credits"> <p class="dwt_author">Ma, M.-S.; Schmitt, R. A.; Laul, J. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">220</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://earthref.org/index.html"> <span id="translatedtitle"><span class="hlt">Earth</span>Ref: Website for Physical and Chemical <span class="hlt">Earth</span> References</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">The <span class="hlt">Earth</span>Ref web site contains several online databases, downloadable modeling tools, and more. The databases include GERM (Geochemical <span class="hlt">Earth</span> Reference Model), the <span class="hlt">Earth</span>Ref Digital Archive, the Seamount Catalog, and Partition Coefficients. A Geophysical Reference <span class="hlt">Earth</span> Model (REM) is currently under construction. The GERM database contains summary data on the <span class="hlt">geochemistry</span> of all reservoirs in the <span class="hlt">Earth</span> and solar system. It includes only peer-reviewed data and is searchable by reservoir, <span class="hlt">element</span>, and reference. The <span class="hlt">Earth</span>Ref Digital Archive contains any type of digital data object associated with the <span class="hlt">Earth</span> Sciences. Data objects may be part of non-published <span class="hlt">Earth</span> Sciences projects ranging from data tables to diagrams to reports to geological maps to videos. The Seamount Catalog includes a searchable database of maps and morphological data sheets, and a library of gridded bathymetry files along with their original multibeam data. The Partition Coefficient database contains Kd (partition coefficient) data for all types of rocks and minerals and for every <span class="hlt">element</span>. Both experimental and empirical data are included in this extensive compilation.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_10");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">221</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23548400"> <span id="translatedtitle">Bioleaching of rare <span class="hlt">earth</span> and radioactive <span class="hlt">elements</span> from red mud using Penicillium tricolor RM-10.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The aim of this work is to investigate biological leaching of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) and radioactive <span class="hlt">elements</span> from red mud, and to evaluate the radioactivity of the bioleached red mud used for construction materials. A filamentous, acid-producing fungi named RM-10, identified as Penicillium tricolor, is isolated from red mud. In our bioleaching experiments by using RM-10, a total concentration of 2% (w/v) red mud under one-step bioleaching process was generally found to give the maximum leaching ratios of the REEs and radioactive <span class="hlt">elements</span>. However, the highest extraction yields are achieved under two-step bioleaching process at 10% (w/v) pulp density. At pulp densities of 2% and 5% (w/v), red mud processed under both one- and two-step bioleaching can meet the radioactivity regulations in China. PMID:23548400</p> <div class="credits"> <p class="dwt_author">Qu, Yang; Lian, Bin</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">222</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24681591"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> recycling from waste phosphor by dual hydrochloric acid dissolution.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">This paper is a comparative study of recycling rare <span class="hlt">earth</span> <span class="hlt">elements</span> from waste phosphor, which focuses on the leaching rate and the technical principle. The traditional and dual dissolution by hydrochloric acid (DHA) methods were compared. The method of dual dissolution by hydrochloric acid has been developed. The Red rare <span class="hlt">earth</span> phosphor (Y0.95Eu0.05)2O3 in waste phosphor is dissolved during the first step of acid leaching, while the Green phosphor (Ce0.67Tb0.33MgAl11O19) and the Blue phosphor (Ba0.9Eu0.1MgAl10O17) mixed with caustic soda are obtained by alkali sintering. The excess caustic soda and NaAlO2 are removed by washing. The insoluble matter is leached by the hydrochloric acid, followed by solvent extraction and precipitation (the DHA method). In comparison, the total leaching rate of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> was 94.6% by DHA, which is much higher than 42.08% achieved by the traditional method. The leaching rate of Y, Eu, Ce and Tb reached 94.6%, 99.05%, 71.45%, and 76.22%, respectively. DHA can decrease the consumption of chemicals and energy. The suggested DHA method is feasible for industrial applications. PMID:24681591</p> <div class="credits"> <p class="dwt_author">Liu, Hu; Zhang, Shengen; Pan, Dean; Tian, Jianjun; Yang, Min; Wu, Maolin; Volinsky, Alex A</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">223</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17208446"> <span id="translatedtitle">Rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in Egyptian granite by instrumental neutron activation analysis.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The mobilization of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in the environment requires monitoring of these <span class="hlt">elements</span> in environmental matrices, in which they are mainly present at trace levels. The similarity in REEs chemical behavior makes the separate determination of each <span class="hlt">element</span> by chemical methods difficult; instrumental neutron activation analysis (INAA), based on nuclear properties of the <span class="hlt">elements</span> to be determined, is a method of choice in trace analysis of REEs and related <span class="hlt">elements</span>. 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 <span class="hlt">elements</span> 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</p> <div class="credits"> <p class="dwt_author">El-Taher, A</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">224</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19860050790&hterms=Peridotite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DPeridotite"> <span id="translatedtitle">Transition region of the <span class="hlt">earth</span>'s upper mantle</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The chemistry of the <span class="hlt">earth</span>'s mantle is discussed using data from cosmochemistry, <span class="hlt">geochemistry</span>, petrology, seismology, and mineral physics. The chondritic <span class="hlt">earth</span>, the upper mantle and the 400-km discontinuity, the transition region, lower mantle mineralogy, and surface wave tomography are examined. Three main issues are addressed: (1) whether the mantle is homogeneous in composition or chemically stratified, (2) whether the major <span class="hlt">element</span> chemistry of the mantle is more similar to upper mantle peridotites or to chondrites, and (3) the nature of the composition of the source region of basalts erupted at midocean ridges.</p> <div class="credits"> <p class="dwt_author">Anderson, D. L.; Bass, J. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">225</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21269172"> <span id="translatedtitle">NEW RARE <span class="hlt">EARTH</span> <span class="hlt">ELEMENT</span> ABUNDANCE DISTRIBUTIONS FOR THE SUN AND FIVE r-PROCESS-RICH VERY METAL-POOR STARS</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">We have derived new abundances of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five <span class="hlt">elements</span> are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other <span class="hlt">elements</span> in individual stars, to produce internally consistent Ba, rare <span class="hlt">earth</span>, and Hf (56 {<=} Z {<=} 72) <span class="hlt">element</span> distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.</p> <div class="credits"> <p class="dwt_author">Sneden, Christopher [Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712 (United States); Lawler, James E.; Den Hartog, Elizabeth A. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Cowan, John J. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Ivans, Inese I. [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States)], E-mail: chris@verdi.as.utexas.edu, E-mail: jelawler@wisc.edu, E-mail: eadenhar@wisc.edu, E-mail: cowan@nhn.ou.edu, E-mail: iii@ociw.edu</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">226</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://cdsweb.cern.ch/record/1166047"> <span id="translatedtitle">New Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">We have derived new abundances of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five <span class="hlt">elements</span> are in good agreement with meteoritic abundances. For the low metallicity sample, these abundances have been combined with new Ce abundances from a companion paper, and reconsideration of a few other <span class="hlt">elements</span> in individual stars, to produce internally-consistent Ba, rare-<span class="hlt">earth</span>, and Hf (56<= Z <= 72) <span class="hlt">element</span> distributions. These have been used in a critical comparison between stellar and solar r-process abundance mixes.</p> <div class="credits"> <p class="dwt_author">Sneden, Christopher; Cowan, John J; Ivans, Inese I; Hartog, Elizabeth A Den</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">227</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006GeCoA..70.3702B"> <span id="translatedtitle">Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the 1991 Mt. Pinatubo silicic melts, Philippines: Implications for ore-forming potential of adakitic magmatism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The dacite pumice erupted from Mt. Pinatubo on June 15, 1991 (whole-rock, rhyolitic groundmass glasses and homogenized melt inclusions) has been analyzed using inductively coupled plasma-mass spectrometry (ICP-MS), nanosecond and femtosecond laser ablation ICP-MS and secondary ion mass spectrometry (SIMS) to evaluate its ore-forming potential. Data suggest that adakite magmas are metal-rich and concentrate ore metals during magmatic differentiation. Sulfides segregate in limited amounts under the hydrous, oxidizing conditions typical of adakitic magmas resulting in incompatible behavior for Au (6-22 ppb), Cu (26-77 ppm), and Pb, Mo, As, and Sb in melts of dacitic to rhyolitic compositions. Metal transfer from this adakite magma to the coexisting aqueous phase was favored by the peraluminous composition of the rhyolitic melt and high aqueous chloride concentrations. Mass balance calculations suggest that the pre-eruptive aqueous phase could have extracted a minimum of 100 t Au and 5 × 10 5 t Cu from the Mt. Pinatubo magma. Our data suggest that intrusives having adakitic signatures are genetically associated with Au-Cu and Cu-Mo mineralization, auriferous porphyry copper deposits, and epithermal gold veins. High H 2O, Cl, Sr/Y, Pb/Ce, Mo/Ce, As/Ce and Sb/Ce in Mt. Pinatubo melts reflect the contribution of deep fluids derived from subducted sediments and altered MORBs in the dacite genesis. The slab-derived fluids carrying mobile <span class="hlt">elements</span> are likely responsible for the enrichment of adakite magmas in gold, associated metals and H 2O, and may explain the exceptional ore-forming potential of adakite magmatism.</p> <div class="credits"> <p class="dwt_author">Borisova, Anastassia Yu.; Pichavant, Michel; Polvé, Mireille; Wiedenbeck, Michael; Freydier, Remi; Candaudap, Frédéric</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">228</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42679007"> <span id="translatedtitle">Determination of Trace Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> in Plant and Soil Samples by Inductively Coupled Plasma-Mass Spectrometry</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in plants and soils. Sample preparation and analytical conditions were investigated to set up a simple routine procedure for measuring rare <span class="hlt">earth</span> <span class="hlt">elements</span>. For prompt sample decomposition, a microwave digestion technique was successfully used with an acid mixture of HCl+HNO3+HF. Detection limits, reproducibility, accuracy</p> <div class="credits"> <p class="dwt_author">Xinde Cao; Ying Chen; Zhimang Gu; Xiaorong Wang</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">229</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T51J..06S"> <span id="translatedtitle">Thickening and propagation of the Pamir plateau: insights from monazite and titanite geochronology and trace-<span class="hlt">element</span> <span class="hlt">geochemistry</span>, eastern Tajikistan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Pamir plateau contains extensive exposures of mid-lower crust, depths not widely exposed in the Tibetan plateau. Determining the spatial and temporal patterns of crustal thickening of the Pamir plateau is critical for understanding how orogenic plateaux are constructed and propagate. The Pamir dome cores consist of upper-amphibolite facies para- and orthogneisses and schists, with the characteristic peak mineral assemblage of kyanite + biotite + garnet ± muscovite in pelites. Thermobarometry indicates peak metamorphism at 600-750°C and 6-10 kbar, representing exhumation depths of 20-35 km (McGraw et al., in review). U-Th-Pb ages of monazite and titanite from the Pamir domes were determined to investigate the timing of thickening and cooling of the mid to lower crust. The closure temperatures of monazite (?700 °C) and titanite (~650-700 °C) make them especially useful geochronometers for dating high-grade metamorphism. Additionally, maps of yttrium (Y) in monazite and garnet and Zr-in-titanite thermometry allow more robust interpretations of isotopic age information. Ages were obtained using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) following the acquisition of backscattered electron and x-ray <span class="hlt">element</span> maps to characterize grain zoning and guide LA-ICP-MS spot placement. The monazites in the rock matrix and as garnet inclusions are chiefly Cenozoic and range from 30 to 18 Ma. They record crystallization during prograde and peak metamorphism, based on textures and compositions. The dated titanites are exclusively polycrystalline aggregates recrystallized during metamorphism. They range from 40 to 10 Ma and define two populations of ~40-32 Ma and ~19-10 Ma. The older titanite ages are restricted to the central Pamir where metamorphic temperatures were <650°C, and the youngest ages come from the southern Pamir, where metamorphic temperatures were above titanite closure to Pb. The oldest ages are therefore likely prograde, and the youngest likely reflect closure during exhumation. The spatial patterns of monazite and titanite ages are consistent with westward thickening and southward exhumation. Westward thickening might have been caused by flow from the topographically higher Tibetan plateau, whereas exhumation may have been controlled by the initiation of intracontinental subduction.</p> <div class="credits"> <p class="dwt_author">Stearns, M. A.; Hacker, B. R.; Kylander-Clark, A. R.; Ratschbacher, L.; Seward, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">230</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/285526"> <span id="translatedtitle">The chemistry of the light rare-<span class="hlt">earth</span> <span class="hlt">elements</span> as determined by electron energy loss spectroscopy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The energy loss spectra of the rare <span class="hlt">earths</span> are characterized by sharp {ital M}{sub 4,5} edges, the relative intensities of which are characteristic of the 4{ital f}-shell occupancy of the excited ion. For the light rare <span class="hlt">earths</span>, the dependence of these relative peak heights on 4{ital f}-shell occupancy is quite pronounced. Thus they may be used to determine the oxidation state of the multivalent <span class="hlt">elements</span> Ce and Pr. The second derivative of the spectrum is shown to be extremely sensitive to the chemical environment. Modern instrumentation and detection techniques allow the oxidation state of Ce and Pr to be determined even when they are present as only minor constituents. {copyright} {ital 1996 American Institute of Physics.}</p> <div class="credits"> <p class="dwt_author">Fortner, J.A.; Buck, E.C. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)] [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">231</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1982GeCoA..46..793S"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> partitioning between minerals from anhydrous spinel peridotite xenoliths</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">REE abundances in minerals from spinel peridotite xenoliths from West Germany, the south-western U.S. and Mongolia decrease in the order clinopyroxene > orthopyroxene > olivine > spinel. While clinopyroxenes are similar in absolute chondrite-normalized concentrations to those known from other studies, orthopyroxenes and olivines are significantly lower in LREE although comparable in HREE. Spinels are much lower in all REE than any previously reported values and are completely negligible for the REE budget of peridotites. Partition coefficients for most orthopyroxene/clinopyroxene pairs increase systematically from La to Lu. Olivine/clinopyroxene and spinel/clinopyroxene partition coefficients increase from the intermediate rare <span class="hlt">earth</span> <span class="hlt">elements</span> to Lu and normally are higher for La compared to Sm. The application of Nagasawa's (1966) elastic lattice model suggests that all heavy but only minor amounts of the light REE substitute into structural positions of orthopyroxene and olivine. Significant differences between orthopyroxene/clinopyroxene partition coefficients for various xenoliths may be assigned to dependences upon equilibration temperature and bulk chemistry. Apart from grain surface contaminations, fluid inclusions which are practically always present in mantle minerals, can highly concentrate light rare <span class="hlt">earth</span> <span class="hlt">elements</span> and thus may be responsible for unexpectedly high concentrations of incompatible <span class="hlt">elements</span> frequently reported for mantle olivines or orthopyroxenes.</p> <div class="credits"> <p class="dwt_author">Stosch, Heinz-Günter</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">232</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012GGG....13.1020H"> <span id="translatedtitle">Online preconcentration ICP-MS analysis of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in seawater</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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 <span class="hlt">elements</span> and elutes the preconcentrated sample directly into the spray chamber of an ICP-MS instrument. The commercially available "seaFAST" system (<span class="hlt">Elemental</span> 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 <span class="hlt">earth</span> 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.</p> <div class="credits"> <p class="dwt_author">Hathorne, Ed C.; Haley, Brian; Stichel, Torben; Grasse, Patricia; Zieringer, Moritz; Frank, Martin</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">233</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1986E%26PSL..80..281S"> <span id="translatedtitle">Trace <span class="hlt">element</span> and Sr and Nd isotope <span class="hlt">geochemistry</span> of peridotite xenoliths from the Eifel (West Germany) and their bearing on the evolution of the subcontinental lithosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Peridotite xenoliths from the Eifel can be divided into incompatible <span class="hlt">element</span>-depleted and -enriched members. The depleted group is restricted to dry lherzolites whereas the enriched group encompasses dry harzburgites, dry websterite and amphibole and/or phlogopite-bearing peridotites. Isotopically the depleted group is very diverse with 143Nd/ 144Nd ranging from ˜ 0.51302 to 0.51355 and 87Sr/ 86Sr from ˜ 0.7041 to 0.7019, thus occupying a field larger than expected for oceanic-type subcontinental mantle. These xenoliths are derived from a mantle which appears to have diverged from a bulk-<span class="hlt">earth</span> Nd and Sr isotopic evolution path ˜ 2 Ga ago as a consequence of partial melting. The combination of high 143Nd/ 144Nd with high 87Sr/ 86Sr in some members of the depleted-xenoliths suite is likely to be the result of incipient reaction with incompatible <span class="hlt">element</span>-enriched fluids in the mantle. In the enriched group such reactions have proceeded further and erased any pre-enrichment isotope memory resulting in a smaller isotopic diversity ( 143Nd/ 144Nd˜ 0.51256-0.51273, 87Sr/ 86Sr˜ 0.7044-0.7032). An evaluation of Sm sbnd Hf and Yb sbnd Hf relationships suggests that the amphibole-bearing lherzolites and harzburgites acquired their high enrichment of light rare <span class="hlt">earth</span> <span class="hlt">elements</span> by fluid infiltration into previously depleted peridotite rather than by silicate melt-induced metasomatism. Upper mantle composed of such metasomatized peridotites does not represent a potential source for the basanites and nephelinites from the Eifel. The isotopic and chemical diversity of the subcontinental lithospheric part of the mantle may result from it having remained isolated from the convecting mantle for times > 1 Ga.</p> <div class="credits"> <p class="dwt_author">Stosch, H.-G.; Lugmair, G. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">234</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70039454"> <span id="translatedtitle"><span class="hlt">Earth</span> Science Information System (ESIS)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">The <span class="hlt">Earth</span> Science Information System (ESIS) was developed in 1981 by the U.S. Geological Survey's Office of the Data Administrator. ESIS serves as a comprehensive data management facility designed to support the coordination, integration, and standardization of scientific, technical, and bibliographic data of the U.S. Geological Survey (USGS). ESIS provides, through an online interactive computer system, referral to information about USGS data bases, data <span class="hlt">elements</span> which are fields in the records of data bases, and systems. The data bases contain information about many subjects from several scientific disciplines such as: geology, geophysics, <span class="hlt">geochemistry</span>, hydrology, cartography, oceanography, geography, minerals exploration and conservation, and satellite data sensing.</p> <div class="credits"> <p class="dwt_author">U.S. Geological Survey</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">235</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014AnGeo..32.1477B"> <span id="translatedtitle">On the origin of falling-tone chorus <span class="hlt">elements</span> in <span class="hlt">Earth</span>'s inner magnetosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Generation of extremely/very low frequency (ELF/VLF) chorus waves in <span class="hlt">Earth</span>'s inner magnetosphere has received increased attention recently because of their significance for radiation belt dynamics. Though past theoretical and numerical models have demonstrated how rising-tone chorus <span class="hlt">elements</span> are produced, falling-tone chorus <span class="hlt">element</span> generation has yet to be explained. Our new model proposes that weak-amplitude falling-tone chorus <span class="hlt">elements</span> can be generated by magnetospheric reflection of rising-tone <span class="hlt">elements</span>. Using ray tracing in a realistic plasma model of the inner magnetosphere, we demonstrate that rising-tone <span class="hlt">elements</span> originating at the magnetic equator propagate to higher latitudes. Upon reflection there, they propagate to lower L-shells and turn into oblique falling tones of reduced power, frequency, and bandwidth relative to their progenitor rising tones. Our results are in good agreement with comprehensive statistical studies of such waves, notably using magnetic field measurements from THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. Thus, we conclude that the proposed mechanism can be responsible for the generation of weak-amplitude falling-tone chorus emissions.</p> <div class="credits"> <p class="dwt_author">Breuillard, H.; Agapitov, O.; Artemyev, A.; Krasnoselskikh, V.; Le Contel, O.; Cully, C. M.; Angelopoulos, V.; Zaliznyak, Y.; Rolland, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">236</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013OptMa..35.1226J"> <span id="translatedtitle">Luminescence and structural properties of RbGdS2 compounds doped by rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (Pr, Ce) doped ternary sulfides of formula RbGd1-xRExS2 were synthesized in the form of crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. The X-ray powder diffraction detected only a single crystalline phase of rhombohedral lattice system. Optical properties of studied systems are investigated by methods of time-resolved luminescence spectroscopy. Thermal stability of the Pr3+ emission is demonstrated. Application potential in the white light-emitting diode solid state lighting or X-ray phosphors is discussed.</p> <div class="credits"> <p class="dwt_author">Jarý, V.; Havlák, L.; Bárta, J.; Mihóková, E.; Nikl, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">237</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5272922"> <span id="translatedtitle">Extractive separation of alkaline-<span class="hlt">earth</span> <span class="hlt">elements</span> in the determination of lithium in brines</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The aim of this work was to investigate the possibility of using D2EHDTPA and D2EHPA to separate lithium from alkaline-<span class="hlt">earth</span> <span class="hlt">elements</span>, with subsequent determination of the lithium in the aqueous phase by the flame-photometric method. Extractive purification makes it possible to lower by an order of magnitude, in comparison to the direct method, the limit of detection of lithium in calcium chloride brines, and also to determine lithium in strontium compounds. The relative standard deviations in the determination of lithium by the method which has been developed do not exceed 0.05.</p> <div class="credits"> <p class="dwt_author">Shatskaya, S.S.; Samoilov, Yu.M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-07-20</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">238</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011MinDe..46..761D"> <span id="translatedtitle">Geology, <span class="hlt">geochemistry</span> and mineralogy of the lignite-hosted Ambassador palaeochannel uranium and multi-<span class="hlt">element</span> deposit, Gunbarrel Basin, Western Australia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Ambassador U and multi-<span class="hlt">element</span> deposit occurs on the SW margin of the Gunbarrel Basin, Western Australia. Low-grade, flat-lying U mineralization averaging about 2 m thick at 0.03% U occurs in lignites at the redox front at the base of the weathering profile within a laterally extensive palaeochannel network. Uranium is principally associated with organic matter within the lignitic matrix, although rare discrete U minerals, such as coffinite and uraninite, are also present. The lignite is also enriched in a suite of other <span class="hlt">elements</span>, principally base metals and sulphur, with concentrations of 0.3 ? 1% Cu, Pb, Ni, Co, Zn and total rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) in some samples. Other <span class="hlt">element</span> enrichments include: Cr, Cs, Sc, Se, Ta, Ti, Th, V and Zr as detrital heavy minerals of Zr, Ti and REE (oxides and silicates) or authigenic minerals of Cu, Bi, Pb, Zn, Ni, Se, Hg, Ti, Cr, Tl, V, U and REE (sulphides, vanadates, selenides, oxides, chlorides and native metals) and diffuse lignite impregnations. The Ambassador deposit probably formed from the convergence of redox-active weathering processes to unique source/host rocks, constrained within the palaeochannel. A proximal source of U and trace <span class="hlt">elements</span> of lamproite/carbonatite origin is probable, as constrained by U-Pb isotope and U-Th disequilibria studies. Uranium and other metals were precipitated syngenetically with organic matter as it was deposited during a humid phase in the Late Eocene. Remobilization subsequently concentrated the metals in the upper 2 m of the lignite. This may have occurred during one or more periods of weathering and associated diagenesis, with the latest episode in the last 300,000 years.</p> <div class="credits"> <p class="dwt_author">Douglas, Grant B.; Butt, Charles R. M.; Gray, David J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">239</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011GeCoA..75.1451S"> <span id="translatedtitle">Systematics of metal-silicate partitioning for many siderophile <span class="hlt">elements</span> applied to <span class="hlt">Earth’s</span> core formation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Superliquidus metal-silicate partitioning was investigated for a number of moderately siderophile (Mo, As, Ge, W, P, Ni, Co), slightly siderophile (Zn, Ga, Mn, V, Cr) and refractory lithophile (Nb, Ta) <span class="hlt">elements</span>. To provide independent constrains on the effects of temperature, oxygen fugacity and silicate melt composition, isobaric (3 GPa) experiments were conducted in piston cylinder apparatus at temperature between 1600 and 2600 °C, relative oxygen fugacities of IW-1.5 to IW-3.5, and for silicate melt compositions ranging from basalt to peridotite. The effect of pressure was investigated through a combination of piston cylinder and multi-anvil isothermal experiments between 0.5 and 18 GPa at 1900 °C. Oxidation states of siderophile <span class="hlt">elements</span> in the silicate melt as well as effect of carbon saturation on partitioning are also derived from these results. For some <span class="hlt">elements</span> (e.g. Ga, Ge, W, V, Zn) the observed temperature dependence does not define trends parallel to those modeled using metal-metal oxide free energy data. We correct partitioning data for solute interactions in the metallic liquid and provide a parameterization utilized in extrapolating these results to the P- T- X conditions proposed by various core formation models. A single-stage core formation model reproduces the mantle abundances of several siderophile <span class="hlt">elements</span> (Ni, Co, Cr, Mn, Mo, W, Zn) for core-mantle equilibration at pressures from 32 to 42 GPa along the solidus of a deep peridotitic magma ocean (˜3000 K for this pressure range) and oxygen fugacities relevant to the FeO content of the present-day mantle. However, these P- T- fO 2 conditions cannot produce the observed concentrations of Ga, Ge, V, Nb, As and P. For more reducing conditions, the P- T solution domain for single stage core formation occurs at subsolidus conditions and still cannot account for the abundances of Ge, Nb and P. Continuous core formation at the base of a magma ocean at P- T conditions constrained by the peridotite liquidus and fixed fO 2 yields concentrations matching observed values for Ni, Co, Cr, Zn, Mn and W but underestimates the core/mantle partitioning observed for other <span class="hlt">elements</span>, notably V, which can be reconciled if accretion began under reducing conditions with progressive oxidation to fO 2 conditions consistent with the current concentration of FeO in the mantle as proposed by Wade and Wood (2005). However, neither oxygen fugacity path is capable of accounting for the depletions of Ga and Ge in the <span class="hlt">Earth</span>'s mantle. To better understand core formation, we need further tests integrating the currently poorly-known effects of light <span class="hlt">elements</span> and more complex conditions of accretion and differentiation such as giant impacts and incomplete equilibration.</p> <div class="credits"> <p class="dwt_author">Siebert, Julien; Corgne, Alexandre; Ryerson, Frederick J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">240</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/21838699"> <span id="translatedtitle">Effects of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and REE-binding proteins on physiological responses in plants.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs), which include 17 <span class="hlt">elements</span> 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</p> <div class="credits"> <p class="dwt_author">Liu, Dongwu; Wang, Xue; Chen, Zhiwei</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-02-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_11");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a 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href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a style="font-weight: bold;">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_14");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">241</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2015E%26PSL.411..142E"> <span id="translatedtitle">Partitioning of light lithophile <span class="hlt">elements</span> during basalt eruptions on <span class="hlt">Earth</span> and application to Martian shergottites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">An enigmatic record of light lithophile <span class="hlt">element</span> (LLE) zoning in pyroxenes in basaltic shergottite meteorites, whereby LLE concentrations decrease dramatically from the cores to the rims, has been interpreted as being due to partitioning of LLE into a hydrous vapor during magma ascent to the surface on Mars. These trends are used as evidence that Martian basaltic melts are water-rich (McSween et al., 2001). Lithium and boron are light lithophile <span class="hlt">elements</span> (LLE) that partition into volcanic minerals and into vapor from silicate melts, making them potential tracers of degassing processes during magma ascent to the surface of <span class="hlt">Earth</span> and of other planets. While LLE degassing behavior is relatively well understood for silica-rich melts, where water and LLE concentrations are relatively high, very little data exists for LLE abundance, heterogeneity and degassing in basaltic melts. The lack of data hampers interpretation of the trends in the shergottite meteorites. Through a geochemical study of LLE, volatile and trace <span class="hlt">elements</span> in olivine-hosted melt inclusions from Kilauea Volcano, Hawaii, it can be demonstrated that lithium behaves similarly to the light to middle rare <span class="hlt">Earth</span> <span class="hlt">elements</span> during melting, magma mixing and fractionation. Considerable heterogeneity in lithium and boron is inherited from mantle-derived primary melts, which is dominant over the fractionation and degassing signal. Lithium and boron are only very weakly volatile in basaltic melt erupted from Kilauea Volcano, with vapor-melt partition coefficients <0.1. Degassing of LLE is further inhibited at high temperatures. Pyroxene and associated melt inclusion LLE concentrations from a range of volcanoes are used to quantify lithium pyroxene-melt partition coefficients, which correlate negatively with melt H2O content, ranging from 0.13 at low water contents to <0.08 at H2O contents >4 wt%. The observed terrestrial LLE partitioning behavior is extrapolated to Martian primitive melts through modeling. The zoning observed in the shergottite pyroxenes is only consistent with degassing of LLE from a Martian melt near its liquidus temperature if the vapor-melt partition coefficient was an order of magnitude larger than observed on <span class="hlt">Earth</span>. The range in LLE and trace <span class="hlt">elements</span> observed in shergottite pyroxenes are instead consistent with concurrent mixing and fractionation of heterogeneous melts from the mantle.</p> <div class="credits"> <p class="dwt_author">Edmonds, Marie</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">242</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57768930"> <span id="translatedtitle">Sample Preparation for Determination of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> in Geological Samples by ICP-MS: A Critical Review</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The presence of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) in geological materials provides important information about the formation and the geochemical processes suffered by the rocks. Therefore, there is a constant necessity for accurate data and reliable and fast analytical methods. However, the low concentrations of these <span class="hlt">elements</span> typically found in rocks require quantification by sufficiently sensitive techniques, such as Inductively Coupled</p> <div class="credits"> <p class="dwt_author">Frederico Garcia Pinto; Rainério Escalfoni Junior; Tatiana Dillenburg SaintPierre</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">243</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19850010583&hterms=Plate+Tectonics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3D%2522Plate%2BTectonics%2522"> <span id="translatedtitle"><span class="hlt">Earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The following aspects of the planet <span class="hlt">Earth</span> are discussed: plate tectonics, the interior of the planet, the formation of the <span class="hlt">Earth</span>, and the evolution of the atmosphere and hydrosphere. The <span class="hlt">Earth</span>'s crust, mantle, and core are examined along with the bulk composition of the planet.</p> <div class="credits"> <p class="dwt_author">Carr, M. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">244</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUFM.B21B0895S"> <span id="translatedtitle">Behavior of rare <span class="hlt">earth</span> and trace <span class="hlt">elements</span> in Lake Tanganyika and its three major tributaries</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Water samples were collected, during the rainy and dry seasons 2003, from three major rivers and several locations of the Lake Tanganyika. They were directly filtered (0.45 im pore size) into pre-washed polyethylene bottles, and acidified at pH 2. Finnigan <span class="hlt">Element</span> 2 high resolution (HR)-IC-MPS was used to measure trace and rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) concentrations under clean laboratory conditions, and (115In) was used as an internal standard. Because of the close relationship between light rare <span class="hlt">earth</span> <span class="hlt">element</span> (LREE) and Fe, riverine REE of the three were used to study the process trace <span class="hlt">element</span> scavenging by Fe oxyhydroxides in three different two sub-basins of the lake. This confirmed by the significant positive correlation between Nd and Fe. The vertical distribution of Fe and Mn oxides were also used to investigate removal and release of trace <span class="hlt">elements</span> in the water column. The normalized lacustrine REE to their riverine counterpart showed a gradual removal of REE across the lake, which was in the order of LREE>MREE>HREE. Hence, the rivers are the sole source of the lacustrine REE abundance. Coincidence of Fe maxima with those of Ce anomalies and La indicates that trace <span class="hlt">element</span> profiles are chiefly controlled by the coating of Fe oxyhydroxides through oxidation of Fe2+ to Fe3+ under high dissolved oxygen contents and pH and vice versa. Due to differences in hydrodynamics between the extreme ends of the lake (upwelling in the southern end during the dry season), high mixing between bottom water and surface was observed at the surface in the Southern Basin while the mixing occurred mainly between 40 m and 80 m depth in the Northern Basin. There was also a clear similarity between Ba and NO3- and PO43- profiles in the southern end of the lake, supporting the idea that deep anoxic water, rich in nutrients and trace <span class="hlt">elements</span>, are bought the surface during this period of intensive upwelling. In conclusion, the surface water chemical compositions of Lake Tanganyika are controlled by fluvial inputs and the seasonal changes in hydrodynamics across the lake.</p> <div class="credits"> <p class="dwt_author">Sako, A.; Johnson, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">245</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EOSTr..93R.202S"> <span id="translatedtitle">While China's dominance in rare <span class="hlt">earths</span> dips, concerns remain about these and other <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">China's dominance in the production of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) peaked with that nation producing 97% of them in 2010; this number already has dipped to 90% in 2012 as mines in other nations are coming online, according to REE expert Karl Gschneidner Jr., a professor at Iowa State University's Ames Laboratory. Chinese production could drop to 60% by 2014, with production increasing at mines in the United States and other countries, he said. However, this reduction in China's share of REE production does not signal an end to the production crisis in REEs and other critical minerals, Gschneidner and others noted during a 1 May panel discussion on critical materials shortages at the AGU Science Policy Conference in Washington, D. C. REEs are a group of 17 chemically similar metallic <span class="hlt">elements</span> used in a variety of electronic, optical, magnetic, and catalytic applications, and despite their name, they are relatively plentiful in the <span class="hlt">Earth</span>'s crust. China's control of known REE reserves has dropped from 75% in 1975 to 30.9% in 2012, with other regions also having large reserves, including the Commonwealth of Independent States (some former Soviet Republic states), the United States, and Australia, according to Gschneidner. Critical minerals are mineral commodities that are particularly important for a nation's economy or national defense that could potentially face supply disruptions.</p> <div class="credits"> <p class="dwt_author">Showstack, Randy</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">246</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24657942"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> components in atmospheric particulates in the Bayan Obo mine region.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The Bayan Obo mine, located in Inner Mongolia, China, is the largest light rare <span class="hlt">earth</span> body ever found in the world. The research for rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) enrichment in atmospheric particulates caused by mining and ore processing is fairly limited so far. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 ?m (PM10) were collected around the Bayan Obo mine region, in August 2012 and March 2013, to analyze the levels and distributions of REEs in particles. The total concentrations of REEs for TSP were 149.8 and 239.6 ng/m(3), and those for PM10 were 42.8 and 68.9 ng/m(3), in August 2012 and March 2013, respectively. Enrichment factor was calculated for all 14 REEs in the TSP and PM10 and the results indicated that REEs enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in springtime. The spatial distribution of REEs in TSP showed a strong gradient concentration in the prevailing wind direction. REE chondrite normalized patterns of TSP and PM10 were similar and the normalized curves inclined to the right side, showing the conspicuous fractionation between the light REEs and heavy REE, which supported by the chondrite normalized concentration ratios calculated for selected <span class="hlt">elements</span> (La(N)/Yb(N), La(N)/Sm(N), Gd(N)/Yb(N)). PMID:24657942</p> <div class="credits"> <p class="dwt_author">Wang, Lingqing; Liang, Tao; Zhang, Qian; Li, Kexin</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">247</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70018161"> <span id="translatedtitle">Record of middle Pleistocene climate change from Buck Lake, Cascade Range, southern Oregon - Evidence from sediment magnetism, trace-<span class="hlt">element</span> <span class="hlt">geochemistry</span>, and pollen</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Comparison of systematic variations in sediment magnetic properties to changes in pollen assemblages in middle Pleistocene lake sediments from Buck Lake indicates that the magnetic properties are sensitive to changes in climate. Buck Lake is located in southern Oregon just east of the crest of the Cascade Range. Lacustrine sediments, from 5.2 to 19.4 m in depth in core, contain tephra layers with ages of ???300-400 ka at 9.5 m and ???400-470 ka at 19.9 m. In these sediments magnetic properties reflect the absolute amount and relative abundances of detrital Fe-oxide minerals, titanomagnetite and hematite. The lacustrine section is divided into four zones on the basis of magnetic properties. Two zones (19.4-17.4 m and 14.5-10.3 m) of high magnetic susceptibility contain abundant Fe oxides and correspond closely to pollen zones that are indicative of cold, dry environments. Two low-susceptibility zones (17.4-14.5 m and 10.3-5.3 m) contain lesser amounts of Fe oxides and largely coincide with zones of warm-climate pollen. Transitions from cold to warm climate based on pollen are preceded by sharp changes in magnetic properties. This relation suggests that land-surface processes responded to these climate changes more rapidly than did changes in vegetation as indicated by pollen frequencies. Magnetic properties have been affected by three factors: (1) dissolution of Fe oxides, (2) variation in heavy-mineral content, and (3) variation in abundance of fresh volcanic rock fragments. Trace-<span class="hlt">element</span> <span class="hlt">geochemistry</span>, employing Fe and the immobile <span class="hlt">elements</span> Ti and Zr, is utilized to detect postdepositional dissolution of magnetic minerals that has affected the magnitude of magnetic properties with little effect on the pattern of magnetic-property variation. Comparison of Ti and Zr values, proxies for heavy-mineral content, to magnetic properties demonstrates that part of the variation in the amount of magnetite and nearly all of the variation in the amount of hematite are due to changes in heavy-mineral content. Variation in the quantity of fresh volcanic rock fragments is the other source of change in magnetite content. Magnetic-property variations probably arise primarily from changes in peak runoff. At low to moderate flows magnetic properties reflect only the quantities of heavy minerals derived from soil and highly weathered rock in the catchment. At high flows, however, fresh volcanic rock fragments may be produced by breaking of pebbles and cobbles, and such fragments greatly increase the magnetite content of the resulting sediment. Climatically controlled factors that would affect peak runoff levels include the accumulation and subsequent melting of winter snow pack, the seasonality of precipitation, and the degree of vegetation cover of the land surface. Our results do not distinguish amont the possible contributions of these disparate factors.</p> <div class="credits"> <p class="dwt_author">Rosenbaum, J.G.; Reynolds, R.L.; Adam, D.P.; Drexler, J.; Sarna-Wojcicki, A. M.; Whitney, G.C.</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">248</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25283836"> <span id="translatedtitle">Recovery of rare <span class="hlt">earth</span> <span class="hlt">elements</span> from the sulfothermophilic red alga Galdieria sulphuraria using aqueous acid.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The demand for rare <span class="hlt">earth</span> <span class="hlt">elements</span> has increased dramatically in recent years because of their numerous industrial applications, and considerable research efforts have consequently been directed toward recycling these materials. The accumulation of metals in microorganisms is a low-cost and environmentally friendly method for the recovery of metals present in the environment at low levels. Numerous metals, including rare <span class="hlt">earth</span> <span class="hlt">elements</span>, can be readily dissolved in aqueous acid, but the efficiency of metal biosorption is usually decreased under the acidic conditions. In this report, we have investigated the use of the sulfothermophilic red alga Galdieria sulphuraria for the recovery of metals, with particular emphasis on the recovery of rare <span class="hlt">earth</span> metals. Of the five different growth conditions investigated where G. sulphuraria could undergo an adaptation process, Nd(III), Dy(III), and Cu(II) were efficiently recovered from a solution containing a mixture of different metals under semi-anaerobic heterotrophic condition at a pH of 2.5. G. sulphuraria also recovered Nd(III), Dy(III), La(III), and Cu(II) with greater than 90 % efficiency at a concentration of 0.5 ppm. The efficiency remained unchanged at pH values in the range of 1.5-2.5. Furthermore, at pH values in the range of 1.0-1.5, the lanthanoid ions were collected much more efficiently into the cell fractions than Cu(II) and therefore successfully separated from the Cu(II) dissolved in the aqueous acid. Microscope observation of the cells using alizarin red suggested that the metals were accumulating inside of the cells. Experiments using dead cells suggested that this phenomenon was a biological process involving specific activities within the cells. PMID:25283836</p> <div class="credits"> <p class="dwt_author">Minoda, Ayumi; Sawada, Hitomi; Suzuki, Sonoe; Miyashita, Shin-Ichi; Inagaki, Kazumi; Yamamoto, Takaiku; Tsuzuki, Mikio</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">249</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1999JChEd..76..475B"> <span id="translatedtitle">The History and Use of Our <span class="hlt">Earth</span>'s Chemical <span class="hlt">Elements</span>: A Reference Guide (by Robert E. Krebs)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Greenwood Press: Westport, CT, 1998. 282 pp + 25 pp glossary + 37 pp index. 15.9 x 24.1 cm. ISBN 0-313-30123-9. $39.95. This book is an excellent resource for chemical educators at the high school and college levels. The format of the text is consistent and the writing style is clear and concise, making it ideally suited for student use also. The first three chapters serve to introduce the reader to a brief history of chemistry, early models of the atom, and the development of the periodic table. Names of the contributing scientists are mentioned whenever necessary, but the overall purpose of these introductory chapters is simply to lay a foundation for the subsequent seven chapters. A complete glossary of important scientific terms mentioned in the text should allow beginning students to use this book without feeling overwhelmed. Each entry for the 112 <span class="hlt">elements</span> contains the following information: <span class="hlt">elemental</span> symbol, atomic number, period, common valence, atomic weight, natural state, common isotopes, properties, characteristics, abundance, natural sources, history, common uses and compounds, and safety hazards. This information is well organized, with clear headings and separate sections making the book extremely user-friendly. Readers can easily obtain the information they desire without having to skim the full entry for a chosen <span class="hlt">element</span>. One very nice feature of this book is that the <span class="hlt">elements</span> entries are arranged by their locations in the periodic table. For example, chapter 4 contains the alkali metals and alkaline <span class="hlt">earth</span> metals. This organizational scheme allows one to quickly see the patterns and trends within groups of <span class="hlt">elements</span>. This format is significantly better than arranging the <span class="hlt">elements</span> in alphabetical order, which places the entry for sodium far removed from the entries for lithium and potassium. I would highly recommend this book to high school teachers and college chemistry professors. It is well written and is an excellent source of information for both students and educators.</p> <div class="credits"> <p class="dwt_author">Bracken, Reviewed By Jeffrey D.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">250</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/15478941"> <span id="translatedtitle">Distribution characteristics of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in children's scalp hair from a rare <span class="hlt">earths</span> mining area in southern China.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">In order to demonstrate the validity of using scalp hair rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) content as a biomarker of human REEs exposure, data were collected on REEs exposure levels from children aged 11-15 years old and living in an ion-adsorptive type light REEs (LREEs) mining and surrounding areas in southern China. Sixty scalp hair samples were analyzed by ICP-MS for 16 REEs (La Lu, Y and Sc). Sixteen REEs contents in the samples from the mining area (e.g., range: La: 0.14-6.93 microg/g; Nd: 0.09-5.27 microg/g; Gd: 12.2-645.6ng/g; Lu: 0.2-13.3 ng/g; Y: 0.03-1.27 microg/g; Sc: 0.05-0.30 microg/g) were significantly higher than those from the reference area (range: La: 0.04-0.40 microg/g; Nd: 0.04-0.32 microg/g; Gd: 8.3-64.6 ng/g; Lu: 0.4-3.3ng/g; Y: 0.03-0.29 microg/g; Sc: 0.11-0.36 microg/g) and even much higher than those published in the literature. The distribution pattern of REEs in scalp hair from the mining area was very similar to that of REEs in the mine and the atmosphere shrouding that area. In conclusion, the scalp hair REEs contents may indicate not only quantitatively but also qualitatively (distribution pattern) the absorption of REEs from environmental exposure into human body. The children living in this mining area should be regarded as a high-risk group with REEs (especially LREEs) exposure, and their health status should be examined from a REEs health risk assessment perspective. PMID:15478941</p> <div class="credits"> <p class="dwt_author">Tong, Shi-Lu; Zhu, Wang-Zhao; Gao, Zhao-Hua; Meng, Yu-Xiu; Peng, Rui-Ling; Lu, Guo-Cheng</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">251</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011LPI....42.1012Z"> <span id="translatedtitle">Petrography and <span class="hlt">Geochemistry</span> of Lunar Meteorite Dhofar 1442</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Here we present the detailed petrography and <span class="hlt">geochemistry</span> of lunar meteorite Dhofar 1442, the most incompatible-<span class="hlt">element</span>-rich lunar regolith sample ever found, and model its major lithologic components and likely provenance.</p> <div class="credits"> <p class="dwt_author">Zeigler, R. A.; Korotev, R. L.; Jolliff, B. L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">252</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20080026144&hterms=nano&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dnano"> <span id="translatedtitle">'Nano' Morphology and <span class="hlt">Element</span> Signatures of Early Life on <span class="hlt">Earth</span>: A New Tool for Assessing Biogenicity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The relatively young technology of NanoSIMS is unlocking an exciting new level of information from organic matter in ancient sediments. We are using this technique to characterize Proterozoic organic material that is clearly biogenic as a guide for interpreting controversial organic structures in either terrestrial or extraterrestrial samples. NanoSIMS is secondary ion mass spectrometry for trace <span class="hlt">element</span> and isotope analysis at sub-micron resolution. In 2005, Robert et al. [1] combined NanoSIMS <span class="hlt">element</span> maps with optical microscopic imagery in an effort to develop a new method for assessing biogenicity of Precambrian structures. The ability of NanoSIMS to map simultaneously the distribution of organic <span class="hlt">elements</span> with a 50 nm spatial resolution provides new biologic markers that could help define the timing of life s development on <span class="hlt">Earth</span>. The current study corroborates the work of Robert et al. and builds on their study by using NanoSIMS to map C, N (as CN), S, Si and O of both excellently preserved microfossils and less well preserved, non-descript organics in Proterozoic chert from the ca. 0.8 Ga Bitter Springs Formation of Australia.</p> <div class="credits"> <p class="dwt_author">Oehler, D. Z.; Mostefaoui, S.; Meibom, A.; Selo, M.; McKay, D. S.; Robert, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">253</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JVGR..287....1F"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in sinters from the geothermal waters (hot springs) on the Tibetan Plateau, China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The mineralogical and geochemical composition of sinters from the geothermal areas on the Tibetan Plateau was determined. They occur as siliceous, salty and calcareous sinters but biogenic siliceous sinters were also found. The analyses indicate that there are no distinct inter -<span class="hlt">element</span> relationships between individual rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) and other <span class="hlt">elements</span>. Formed from the same geothermal water, the mineralogical and chemical composition of the sinters is influenced by their genesis and formation conditions. The REE distributions depend on the origin of the sinters. Fe-Mn phases in sinters tend to scavenge more REEs from geothermal water. Neither the REE fractionation nor the Ce anomaly seems to be associated with Fe-Mn phases in the sinters. The fourth tetrads of some sinters display weak W-type (concave) effects. In contrast, the third tetrads present large effects in some sinters due to positive Gd anomalies. The origin of the positive Eu anomalies in some sinters seems to be caused by preferential dissolution of feldspars during water-rock interaction. The complexing ligands in geothermal water may contribute significantly to the fractionation of REEs in sinters. The dominant CO32- and HCO3- complexing in geothermal water favors enrichment of heavy REEs in calcareous sinters.</p> <div class="credits"> <p class="dwt_author">Feng, Jin-Liang; Zhao, Zhen-Hong; Chen, Feng; Hu, Hai-Ping</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">254</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFMEP51B0585E"> <span id="translatedtitle">Spatial and temporal dynamics of sediment in contrasted mountainous watersheds (Mexican transvolcanic belt and French Southern Alps) combining river gauging, <span class="hlt">elemental</span> <span class="hlt">geochemistry</span> and fallout radionuclides</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In mountainous environments, an excessive fine sediment supply to the rivers typically leads to an increase in water turbidity, contaminant transport and a rapid filling of reservoirs. This situation is particularly problematic in regions where water reservoirs are used to provide drinking water to large cities (e.g. in central Mexico) or where stream water is used to run hydroelectric power plants (e.g. in the French Southern Alps). In such areas, sediment source areas first need to be delineated and sediment fluxes between hillslopes and the river system must be better understood before implementing efficient erosion control measures. In this context, the STREAMS (« Sediment Transport and Erosion Across MountainS ») project funded by the French National Research Agency (ANR) aims at understanding the spatial and temporal dynamics of sediment at the scale of mountainous watersheds (between 500 - 1000 km2) located in contrasted environments. This 3-years study is carried out simultaneously in a volcanic watershed located in the Mexican transvolcanic belt undergoing a subhumid tropical climate, as well as in a sedimentary watershed of the French Southern Alps undergoing a transitional climate with Mediterranean and continental influences. One of the main specificities of this project consists in combining traditional monitoring techniques (i.e. installation of river gauges, turbidimeters and sediment samplers in several sub-catchments) and sediment fingerprinting using <span class="hlt">elemental</span> <span class="hlt">geochemistry</span> (measured by Instrumental Neutron Activation Analysis - INAA - and Inductively Coupled Plasma - Mass Spectrometry - ICP-MS) and fallout radionuclides (measured by gamma spectrometry). In the French watershed, geochemical analysis allows outlining different sediment sources (e.g. the contribution of calcareous vs. marl-covered sub-watersheds). Radionuclide ratios (e.g.Be-7/Cs-137) allow identifying the dominant erosion processes occurring within the watershed. Areas mostly affected by gully erosion, rill or sheet erosion have been delineated. Furthermore, the measurement of radionuclide content in suspended sediment after the snowmelt suggests that most of this sediment consists in resuspended material rather than on newly eroded soil. In the Mexican watershed, a different contribution of andisols and acrisols to erosion is suspected. Overall, the bulk of erosion is generated by rather small areas within the watershed. In this region characterised by a succession of wet and dry seasons, the Be-7 content in rainfall and sediment has been measured at the scale of a 2.5 km2 sub-watershed in order to better understand the erosion transfer between hillslopes and rivers during the rainy season. This outlines the contribution of individual storms to seasonal erosion. Overall, this study brings important insights about sediment sources and fluxes within these watersheds located in contrasted environments. A further step consists in comparing experimental results with model outputs, and to evaluate the impact of on-going erosion mitigation measures.</p> <div class="credits"> <p class="dwt_author">Evrard, O.; Navratil, O.; Gratiot, N.; Némery, J.; Duvert, C.; Ayrault, S.; Lefèvre, I.; Legout, C.; Bonté, P.; Esteves, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">255</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/15202236"> <span id="translatedtitle">[Speciation and distribution characters of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Baotou Section of the Yellow River].</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">As a whole of water column, suspended matter and surface sediment in the mainstream and the branch taking up industry wastewater, speciation and distribution characters of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) were investigated systemically in the Baotou section of the Yellow River. This study shows that rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the mainstream of the Baotou section of the Yellow River mainly exist in suspended particles, and the dissolved contents are in extremely minute quantities. REEs mainly exist in dissolved particles in the branch taking up industry wastewater, and suspended sigma REE and dissolved sigma REE are obviously higher than those in the mainstream. The change of sigma REE of dissolved particles in water phase along the Baotou section of the Yellow River is very similar to that of sigma REE of suspended particles, and consistent along the main river, it is that sigma REE increase appreciably from the control profile to the keystone discharged section, come to a head in the D site and reduce in the E site. This distribution pattern indicates pile industry wastewater of Baotou to rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the mainstream of the Yellow River, particularly LREE. The REE distribution in the mainstream of the Baotou section of the Yellow River is the same, with LREE enrichment and Eu depletion. But LREE origin of D site is different from the other sites by excursion of LREE distribution curve and other geochemical parameters, they are origin of industry wastewater piled, otherwise the other four sites are origin of loess altiplano. And HREE are origin of loess altiplano in all the sites. The speciation characteristics of REE in the sediments and suspended matter are quite similar with the amount in as follows: residual > bound to carbonates, bound to Fe-Mn oxides > bound to organic matter > exchangeable. REEs exchangeable in surface sediment and suspended matter in the branch taking up industry wastewater are higher than those in the mainstream, it confirms that REEs in the mainstream mainly exist in suspended particles, and mainly exist in dissolved particles in the branch. PMID:15202236</p> <div class="credits"> <p class="dwt_author">He, Jiang; Mi, Na; Kuang, Yun-chen; Fan, Qing-yun; Wang, Xia; Guan, Wei; Li, Gui-hai; Li, Chao-sheng; Wang, Xi-wei</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">256</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013GeCoA.108...63P"> <span id="translatedtitle">Insights into early <span class="hlt">Earth</span> from Barberton komatiites: Evidence from lithophile isotope and trace <span class="hlt">element</span> systematics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Major, minor, and lithophile trace <span class="hlt">element</span> abundances and Nd and Hf isotope systematics are reported for two sets of remarkably fresh, by Archean standards, samples of komatiitic lavas from the 3.48 Ga Komati and the 3.27 Ga Weltevreden Formations of the Barberton Greenstone Belt (BGB) in South Africa. These data are used to place new constraints on the thermal history of the early Archean mantle, on the timing of its differentiation, and on the origin and chemical nature of early mantle reservoirs and their evolution through time. Projected moderate to strong depletions of highly incompatible lithophile trace <span class="hlt">elements</span> and water in the mantle sources of both komatiite systems, combined with the partitioning behavior of V during lava differentiation, are consistent with anhydrous conditions during generation of the komatiite magmas. Komati and Weltevreden lavas are inferred to have erupted with temperatures of ?1600 °C, and, thus, represent the hottest known lavas on <span class="hlt">Earth</span>. The calculated mantle potential temperatures of ?1800 °C for both komatiite systems are 150-200 °C higher than those of contemporary ambient mantle. Combined, these observations are consistent with the origin of these BGB komatiite magmas in mantle plumes in the lower mantle. New Sm-Nd and Lu-Hf isotopic data allow precise determination of initial ?143Nd = +0.46 ± 0.10 and +0.50 ± 0.11 and initial ?176Hf = +1.9 ± 0.3 and +4.7 ± 0.8 for the Komati and the Weltevreden system komatiites, respectively. These positive initial values reflect prior fractionation of Sm/Nd and Lu/Hf in the mantle early in <span class="hlt">Earth</span> history. Conversely, ?142Nd values are 0.0 ± 2.4 and +2.2 ± 4.1 for the Komati and the Weltevreden systems, respectively. These values overlap, within uncertainties, those of modern terrestrial rocks, thus, limiting the magnitudes of possible Sm/Nd fractionations generated by early <span class="hlt">Earth</span> processes in the sources of these rocks. Combined 142,143Nd and Hf isotope and lithophile trace <span class="hlt">element</span> systematics are consistent with formation and long-term isolation of deep-seated mantle domains with fractionated Sm/Nd and Lu/Hf at ca. 4400 Ma. These domains were likely generated as a result of crystallization of a primordial magma ocean, with Mg-perovskite and minor Ca-perovskite acting as fractionating phases. The inferred mantle domains were evidently mixed away by 2.7 Ga on the scale of mantle reservoirs sampled by late Archean komatiite lavas emplaced worldwide.</p> <div class="credits"> <p class="dwt_author">Puchtel, I. S.; Blichert-Toft, J.; Touboul, M.; Walker, R. J.; Byerly, G. R.; Nisbet, E. G.; Anhaeusser, C. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">257</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40923378"> <span id="translatedtitle">Partition coefficients for rare <span class="hlt">earth</span> <span class="hlt">elements</span> in mafic minerals of high silica rhyolites: the importance of accessory mineral inclusions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare <span class="hlt">earth</span> titano-silicate) included within clinopyroxenes from the</p> <div class="credits"> <p class="dwt_author">P MICHAEL</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">258</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JAfES..91...66K"> <span id="translatedtitle">Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> and petrogenesis of the granitoids and high-K andesite hosting gold mineralisation in the Archean Musoma-Mara Greenstone Belt, Tanzania</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Modern and ancient active continental margins are well known for their potential for hosting important gold deposits. The Neoarchean Musoma-Mara Greenstone Belt of the Tanzania Craton is also known for hosting several important gold deposits. Previous geochemical studies of the belt demonstrated that the rocks formed along Neoarchean convergent margins. The host rocks of the three important deposits in this belt had not yet been geochemically investigated. Therefore, we studied the host rocks of the Gokona, Nyabigena and Nyabirama gold deposits in the Neoarchean Musoma-Mara Greenstone Belt of the Tanzania Craton to determine the tectonic setting of their formation and constrain their petrogenesis. The host rocks of the Gokona and Nyabigena deposits are classified as high-K andesite, whereas the host rocks of the Nyabirama deposit are classified primarily as trondhjemite and granite and minor granodiorite (TGG). The high-K andesite and TGG were formed in an active continental margin similar to that of other Neoarchean volcanic rocks found in the Musoma-Mara Greenstone Belt. The host rocks contain low Ni and Cr concentrations and are characterised by negative Eu anomalies (Eu/Eu* = 0.67-0.72 and 0.17-0.6). The chondrite-normalised rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) patterns of the rocks display strong enrichment in light REEs over heavy REEs (high-K andesite (La/Yb)N = 21.7-35.6, and TGG (La/Yb)N = 2.4-94.4). Moreover, the primitive normalised diagrams show enrichment in large-ion lithophile <span class="hlt">elements</span> (Ba, Rb, Th and K), negative Nb and Ta anomalies and depletion in heavy rare <span class="hlt">earth</span> <span class="hlt">elements</span> and high field-strength <span class="hlt">elements</span> (Y and Ti). The high-K andesite has a Nb/Ta value close to that of depleted mantle (mean = 15.0), lower Zr/Sm values (19.4-30.6) and higher concentrations of REEs, large ion lithophile <span class="hlt">elements</span>, Sr (607 ppm) and Y than in the TGG. The TGG has a low mean Nb/Ta value (13.2) and Sr concentration (283 ppm) and a lower amount of HREEs and higher values of Zr/Sm (32.5-91.0) compared to the high-K andesite. However, all of the rock types contain high Ta/Yb and Th/Yb values (high-K andesite and granitoids; mean = 5.9 and 0.8, 17 and 21.3). These characteristics are interpreted as an indication of the formation of the Gokona, Nyabigena and Nyabirama host rocks from the hydrous partial melting of mantle peridotite, similar to the evolution of classical island arc rocks. The primary melts subsequently underwent fractional crystallisation to form high-K andesite, dacite and TGG prior to their extrusion or emplacement in the continental crust.</p> <div class="credits"> <p class="dwt_author">Kazimoto, Emmanuel Owden; Ikingura, Justinian R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">259</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19730043515&hterms=Europium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DEuropium"> <span id="translatedtitle">Rare <span class="hlt">earths</span>, other trace <span class="hlt">elements</span> and iron in Luna 20 samples.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The results of the analysis by neutron activation of six samples from the Luna 20 mission and one sample of less than 1 mm fines from Apollo 16 are reported. The concentrations of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REE) in the samples of fines from Luna 20 and Apollo 16 are less than those found for corresponding materials from the mare areas but a negative Eu anomaly is still present. The concentrations of the REE in fines from Luna 20 are only about two-thirds as great as in the sample of Apollo 16 fines, but the concentration of Co, Sc and Cr are greater by factors ranging from 1.5 to 2.3.</p> <div class="credits"> <p class="dwt_author">Helmke, P. A.; Blanchard, D. P.; Jacobs, J. W.; Haskin, L.; Haskin, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1973-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">260</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24385183"> <span id="translatedtitle">Origin of middle rare <span class="hlt">earth</span> <span class="hlt">element</span> enrichment in acid mine drainage-impacted areas.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The commonly observed enrichment of middle rare <span class="hlt">earth</span> <span class="hlt">elements</span> (MREE) in water sampled in acid mine drainage (AMD)-impacted areas was found to be the result of preferential release from the widespread mineral pyrite (FeS2). Three different mining-impacted sites in Europe were sampled for water, and various pyrite samples were used in batch experiments with diluted sulphuric acid simulating AMD-impacted water with high sulphate concentration and high acidity. All water samples independent on their origin from groundwater, creek water or lake water as well as on the surrounding rock types showed MREE enrichment. Also the pyrite samples showed MREE enrichment in the respective acidic leachate but not always in their total contents indicating a process-controlled release. It is discussed that most probably complexation to sulphite (SO3 (2-)) or another intermediate S-species during pyrite oxidation is the reason for the MREE enrichment in the normalized REE patterns. PMID:24385183</p> <div class="credits"> <p class="dwt_author">Grawunder, Anja; Merten, Dirk; Büchel, Georg</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-06-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_12");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> 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href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a style="font-weight: bold;">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_15");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">261</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/792697"> <span id="translatedtitle">Behavior of Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> In Geothermal Systems; A New Exploration/Exploitation Tool</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The goal of this four-year project was to provide a database by which to judge the utility of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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.</p> <div class="credits"> <p class="dwt_author">Scott A. Wood</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-28</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">262</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25000508"> <span id="translatedtitle">Examination of rare <span class="hlt">earth</span> <span class="hlt">element</span> concentration patterns in freshwater fish tissues.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs or lanthanides) were measured in ten freshwater fish species from a reservoir in Washington State (United States). The REE distribution patterns were examined within fillet and whole body tissues for three size classes. Total concentrations (?REE) ranged from 0.014 to 3.0mgkg(-1) (dry weight) and averaged 0.243mgkg(-1) (dry weight). Tissue concentration patterns indicated that REEs accumulated to a greater extent in organs, viscera, and bone compared to muscle (fillet) tissues. Benthic feeding species (exposed to sediments) exhibited greater concentrations of REEs than pelagic omnivorous or piscivorous fish species. Decreasing REE concentrations were found with increasing age, total length or weight for largescale and longnose suckers, smallmouth bass, and walleye. Concentration patterns in this system were consistent with natural conditions without anthropogenic sources of REEs. These data provide additional reference information with regard to the fate and transport of REEs in freshwater fish tissues in a large aquatic system. PMID:25000508</p> <div class="credits"> <p class="dwt_author">Mayfield, David B; Fairbrother, Anne</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">263</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JPhB...45b5001D"> <span id="translatedtitle">Light shifts and magic wavelengths for heavy alkaline <span class="hlt">earth</span> <span class="hlt">elements</span>: Ba and Ra</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In this paper, we investigate light shifts of heavy alkaline <span class="hlt">earth</span> <span class="hlt">elements</span> barium (Ba) and radium (Ra), which are interesting for optical lattice clocks and for permanent electric dipole moment searches. Detailed knowledge is required in the design of efficient loading of atoms from a magneto-optical trap into an optical dipole trap, to facilitate Doppler cooling while trapping and to achieve longer lifetimes of the trapped atoms with reduced heating rates. The wavelength dependence of light shifts of the ns2 1S0 ground state, the nsnp 3P1 and ns(n - 1)d 1D2 excited states in barium (n = 6) and the n s2 1S0 ground state, the nsnp 3P1 and ns(n - 1)d 3D2 excited states in radium (n = 7) are calculated. Several magic wavelengths in the visible and infrared regions accessible with commercial lasers for optical dipole trapping of Ba and Ra are identified.</p> <div class="credits"> <p class="dwt_author">Dammalapati, U.; Santra, B.; Willmann, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">264</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1984Metic..19...69E"> <span id="translatedtitle">Distribution of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and uranium in various components of ordinary chondrites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) and uranium were studied for their distributions in various component phases of four ordinary chondrites. Kesen (H4), Richardton (H5), Bruderheim (L6), and Saint Severin (LL6). A selective dissolution method was applied for the phase fractionation. The REE were analysed by neutron activation analysis, and U was determined by neutron-induced fission tracks. The present study revealed that both REE and U are highly enriched in the Ca-phosphate minerals with different enrichment factors, implying chemical fractionation between them. The phosphates seem to be responsible for more than 80 percent of the light REE in all chondrites. On the other hand, only 20-40 percent of the total U resides in the Ca-phosphates. This difference in enrichments might have been caused through the levels of metamorphic activity on the meteoritic parent bodies.</p> <div class="credits"> <p class="dwt_author">Ebihara, M.; Honda, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">265</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001GeoRL..28.2707G"> <span id="translatedtitle">Effects of continents on <span class="hlt">Earth</span> cooling: Thermal blanketing and depletion in radioactive <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Estimate of mantle heat flow under continental shields are very low, indicating a strong insulating effect of continents on mantle heat loss. This effect is investigated with a simple approach: continents are introduced in an <span class="hlt">Earth</span> cooling model as perfect thermal insulators. Continental growth rate has then a strong influence on mantle cooling. Various continental growth models are tested and are used to compute the mantle depletion in radioactive <span class="hlt">elements</span> as a function of continental crust extraction. Results show that the thermal blanketing effect of continents strongly affects mantle cooling, and that mantle depletion must be taken into account in order not to overestimate mantle heat loss. In order to obtain correct oceanic heat flow for present time, continental growth must begin at least 3 Gy ago and steady-state for continental area must be reached for at least 1.5 Gy in our cooling model.</p> <div class="credits"> <p class="dwt_author">Grigné, Cécile; Labrosse, Stéphane</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">266</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42382885"> <span id="translatedtitle">Beryllium—<span class="hlt">Geochemistry</span>, Mineralogy and Beneficiation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper presents a review of the geology, <span class="hlt">geochemistry</span> and mineralogy of beryllium, and methods of beneficiation of beryl including the safety measures to be adopted while crushing and grinding of beryllium minerals.A typical lithophile <span class="hlt">element</span>, beryllium forms a characteristic four fold coordination with oxygen forming the [BeO] complex. Geochemically it accumulates in the acid and alkalic magmas during magmatic</p> <div class="credits"> <p class="dwt_author">N. Krishna Rao; T. Sreenivas</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">267</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014MinDe.tmp...43S"> <span id="translatedtitle">Geology and market-dependent significance of rare <span class="hlt">earth</span> <span class="hlt">element</span> resources</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">China started to produce rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in the 1980s, and since the mid-1990s, it has become the dominant producer. Rare <span class="hlt">earth</span> <span class="hlt">element</span> export quotas first introduced by the Chinese government in the early 2000s were severely reduced in 2010 and 2011. This led to strong government-created disparity between prices within China and the rest of the world. Industrialized countries identified several REEs as strategic metals. Because of rapid price increases of REE outside of China, we have witnessed a world-scale REE exploration rush. The REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, monazite ± apatite veins, ion adsorption clays, placers, and some deep ocean sediments. REE could also be derived as a by-product of phosphate fertilizer production, U processing, mining of Ti-Zr-bearing placers, and exploitation of Olympic Dam subtype iron oxide copper gold (IOCG) deposits. Currently, REEs are produced mostly from carbonatite-related deposits, but ion adsorption clay deposits are an important source of heavy REE (HREE). Small quantities of REE are derived from placer deposits and one peralkaline intrusion-related deposit. The ideal REE development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia. REE grade, HREE/light REE (LREE) ratio of the mineralization, tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen potential development projects. As REEs are considered strategic metals from economic, national security, and environmental points of view, technical and economic parameters alone are unlikely to be used in REE project development decision-making. Recycling of REE is in its infancy and unless legislated, in the short term, it is not expected to contribute significantly to the supply of REE.</p> <div class="credits"> <p class="dwt_author">Simandl, G. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">268</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014MinDe..49..889S"> <span id="translatedtitle">Geology and market-dependent significance of rare <span class="hlt">earth</span> <span class="hlt">element</span> resources</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">China started to produce rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in the 1980s, and since the mid-1990s, it has become the dominant producer. Rare <span class="hlt">earth</span> <span class="hlt">element</span> export quotas first introduced by the Chinese government in the early 2000s were severely reduced in 2010 and 2011. This led to strong government-created disparity between prices within China and the rest of the world. Industrialized countries identified several REEs as strategic metals. Because of rapid price increases of REE outside of China, we have witnessed a world-scale REE exploration rush. The REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, monazite ± apatite veins, ion adsorption clays, placers, and some deep ocean sediments. REE could also be derived as a by-product of phosphate fertilizer production, U processing, mining of Ti-Zr-bearing placers, and exploitation of Olympic Dam subtype iron oxide copper gold (IOCG) deposits. Currently, REEs are produced mostly from carbonatite-related deposits, but ion adsorption clay deposits are an important source of heavy REE (HREE). Small quantities of REE are derived from placer deposits and one peralkaline intrusion-related deposit. The ideal REE development targets would be located in a politically stable jurisdiction with a pro-mining disposition such as Canada and Australia. REE grade, HREE/light REE (LREE) ratio of the mineralization, tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen potential development projects. As REEs are considered strategic metals from economic, national security, and environmental points of view, technical and economic parameters alone are unlikely to be used in REE project development decision-making. Recycling of REE is in its infancy and unless legislated, in the short term, it is not expected to contribute significantly to the supply of REE.</p> <div class="credits"> <p class="dwt_author">Simandl, G. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">269</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70044201"> <span id="translatedtitle">A major light rare-<span class="hlt">earth</span> <span class="hlt">element</span> (LREE) resource in the Khanneshin carbonatite complex, southern Afghanistan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">The rapid rise in world demand for the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) has expanded the search for new REE resources. We document two types of light rare-<span class="hlt">earth</span> <span class="hlt">element</span> (LREE)-enriched rocks in the Khanneshin carbonatite complex of southern Afghanistan: type 1 concordant seams of khanneshite-(Ce), synchysite-(Ce), and parisite-(Ce) within banded barite-strontianite alvikite, and type 2 igneous dikes of coarse-grained carbonatite, enriched in fluorine or phosphorus, containing idiomorphic crystals of khanneshite-(Ce) or carbocernaite. Type 1 mineralized barite-strontianite alvikite averages 22.25 wt % BaO, 4.27 wt % SrO, and 3.25 wt % ? LREE2O3 (sum of La, Ce, Pr, and Nd oxides). Type 2 igneous dikes average 14.51 wt % BaO, 5.96 wt % SrO, and 3.77 wt % ? LREE2O3. A magmatic origin is clearly indicated for the type 2 LREE-enriched dikes, and type 1 LREE mineralization probably formed in the presence of LREE-rich hydrothermal fluid. Both types of LREE mineralization may be penecontemporaneous, having formed in a carbonate-rich magma in the marginal zone of the central vent, highly charged with volatile constituents (i.e., CO2, F, P2O5), and strongly enriched in Ba, Sr, and the LREE. Based on several assumptions, and employing simple geometry for the zone of LREE enrichment, we estimate that at least 1.29 Mt (million metric tonnes) of LREE2O3 is present in this part of the Khanneshin carbonatite complex.</p> <div class="credits"> <p class="dwt_author">Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Horton, Forrest; Buttleman, Kim; Scott, Emily R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">270</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/21324705"> <span id="translatedtitle">Natural radioactivity and rare <span class="hlt">earth</span> <span class="hlt">elements</span> in feldspar samples, Central Eastern desert, Egypt.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The pegmatite bodies of the Eastern Desert of Egypt are widely distributed especially along the Marsa-Alam-Idfu road. The Abu Dob area covers about 150km(2) of the Arabian Nubian shield at the central part of the Eastern Desert of Egypt. Most of the pegmatite is zoned; the zonation starts with milky quartz at the core followed by alkali feldspar at the margins. The feldspars vary in color from rose to milky and in composition from K-feldspar to Na-feldspar, sometimes interactions of both types are encountered. Thirteen feldspar samples were collected from different locations in the Abu Dob area for measuring the natural radioactivity of (238)U, (232)Th and (40)K using an HPGe detector. The variation in concentration of radionuclides for the area under investigation can be classified into regions of high, medium and low natural radioactivity. The average concentration in BqKg(-1) has been observed to be from 9.5 to 183675.7BqKg(-1) for (238)U, between 6.1 and 94,314.2BqKg(-1) for (232)Th and from 0 to 7894.6BqKg(-1) for (40)K. Radium equivalent activities (Ra(eq)), dose rate (D(R)) and external hazard (H(ex)) have also been determined. In the present work, the concentration of rare <span class="hlt">earth</span> <span class="hlt">elements</span> are measured for two feldspar samples using two techniques, Environmental Scanning Electron microscope XIL 30 ESEM, Philips, and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The existence of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in this area are very high and can be used in different important industries. PMID:21324705</p> <div class="credits"> <p class="dwt_author">Walley El-Dine, Nadia; El-Shershaby, Amal; Afifi, Sofia; Sroor, Amany; Samir, Eman</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">271</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/16038502"> <span id="translatedtitle">X-ray fluorescence analysis of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in rocks using low dilution glass beads.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Major and trace <span class="hlt">elements</span> (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare <span class="hlt">earth</span> <span class="hlt">elements</span>. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 <span class="hlt">elements</span> showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 <span class="hlt">elements</span> in four rhyolitic and granitic rocks from Japan. PMID:16038502</p> <div class="credits"> <p class="dwt_author">Nakayama, Kenichi; Nakamura, Toshihiro</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">272</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012AGUFMIN23C1524W"> <span id="translatedtitle">Structural <span class="hlt">Elements</span> in a Persistent Identifier Infrastructure and Resulting Benefits for the <span class="hlt">Earth</span> Science Community</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We propose a wide adoption of structural <span class="hlt">elements</span> (typed links, collections, trees) in the Handle System to improve identification and access of scientific data, metadata and software as well as traceability of data provenance. Typed links target the issue of data provenance as a means to assess the quality of scientific data. Data provenance is seen here as a directed acyclic graph with nodes representing data and vertices representing derivative operations (Moreau 2010). Landing pages can allow a human user to explore the provenance graph back to the primary unprocessed data, thereby also giving credit to the original data producer. As in <span class="hlt">Earth</span> System Modeling no single infrastructure with complete data lifecycle coverage exists, we propose to split the problem domain in two parts. Project-specific infrastructures such as the German project C3-Grid or the <span class="hlt">Earth</span> System Grid Federation (ESGF) for CMIP5 data are aware of data and data operations (Toussaint et al. 2012) and can thus detect and accumulate single nodes and vertices in the provenance graph, assigning Handles to data, metadata and software. With a common schema for typed links, the provenance graph is established as downstream infrastructures refer incoming Handles. Data in this context is for example hierarchically structured <span class="hlt">Earth</span> System model output data, which receives DataCite DOIs only for the most coarse-granular <span class="hlt">elements</span>. Using Handle tree structures, the lower levels of the hierarchy can also receive Handles, allowing authors to more precisely identify the data they used (Lawrence et al. 2011). We can e.g. define a DOI for just the 2m-temperature variable of CMIP5 data across many CMIP5 experiments or a DOI for model and observational data coming from different sources. The structural <span class="hlt">elements</span> should be implemented through Handle values at the Handle infrastructure level for two reasons. Handle values are more durable than downstream websites or databases, and thus the provenance chain does not break if individual links become unavailable. Secondly, a single service cannot interpret links if downstream solutions differ in their implementation schemas. Emerging efforts driven by the European Persistent Identifier Consortium (EPIC) aim to establish a default mechanism for structural <span class="hlt">elements</span> at the Handle level. We motivate to make applications, which take part in the data lifecycle, aware of data derivation provenance and let them provide additional <span class="hlt">elements</span> to the provenance graph. Since they are also Handles, DataCite DOIs can act as a corner stone and provide an entry point to discover the provenance graph. References B. Lawrence, C. Jones, B. Matthews, S. Pepler, and S. Callaghan, "Citation and peer review of data: Moving towards formal data publication," Int. J. of Digital Curation, vol. 6, no. 2, 2011. L. Moreau, "The foundations for provenance on the web," Foundations and Trends® in Web Science, vol. 2, no. 2-3, pp. 99-241, 2010. F. Toussaint, T. Weigel, H. Thiemann, H. Höck, M. Stockhause: "Application Examples for Handle System Usage", submitted to AGU 2012 session IN009.</p> <div class="credits"> <p class="dwt_author">Weigel, T.; Toussaiant, F.; Stockhause, M.; Höck, H.; Kindermann, S.; Lautenschlager, M.; Ludwig, T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">273</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.sci.uidaho.edu/geol423/"> <span id="translatedtitle">Principals of <span class="hlt">Geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This resource is the homepage of a <span class="hlt">geochemistry</span> course taught by Professor Scott Wood at the University of Idaho. The homepage has links to lecture topics, a course outline, and tests with answers. <span class="hlt">Geochemistry</span> students will find the site helpful for review or clarification of various topics.</p> <div class="credits"> <p class="dwt_author">Wood, Scott P.; Sciences, University O.</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">274</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.acg.uwa.edu.au/__data/page/2035/1100_EIGG_Rego_v8.pdf"> <span id="translatedtitle">Environmental Inorganic <span class="hlt">Geochemistry</span> Group</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">mining: the mine site as a pollution source 0930 The role of water ­ an exceptional substance 1000Environmental Inorganic <span class="hlt">Geochemistry</span> Group Environmental <span class="hlt">Geochemistry</span> of Mine Site Pollution. Sustainability in mining requires that pollution issues are addressed from the planning stage, through operations</p> <div class="credits"> <p class="dwt_author">Tobar, Michael</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">275</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24342358"> <span id="translatedtitle">Effects of exogenous rare <span class="hlt">earth</span> <span class="hlt">elements</span> on phosphorus adsorption and desorption in different types of soils.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Phosphorus (P) is an important biogeochemical <span class="hlt">element</span> and the environmental fate of P receives increasing attention. Through batch equilibration experiments, the adsorption and desorption of P in the absence and presence of exogeneous rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) were investigated in five types of agricultural soil samples collected from China. The results showed that the addition of different doses of REEs had influences on P adsorption processes in the soils, and there were differences in different soil types and different P concentrations of the P solutions. The amount of P adsorption tended to decline when the five types of soils were amended with low concentrations of REEs. The characteristics of P adsorption were more complicated when high concentrations of REEs were added to the different soils. Affected by the high concentrations of REEs, when the P concentration of the P solution added to soils was less than 20 mg L(-1), the rate of P adsorption tended to increase in all the five types of soils. However, when the P concentration of the P solution added to soil was greater than 30 mg L(-1), the rate of P adsorption tended to decrease. The Langmuir equation fitted P adsorption in all the five types of soils well. Compared with the control, when soil samples were amended with REEs, the P desorption rates of the five types of soils increased. PMID:24342358</p> <div class="credits"> <p class="dwt_author">Wang, Lingqing; Liang, Tao</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">276</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.windows2universe.org/earth/earth.html"> <span id="translatedtitle"><span class="hlt">Earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on our plant <span class="hlt">Earth</span>. There is a section about water on <span class="hlt">earth</span> and its many different varities, like freshwater, groundwater, and frozen water. There is information about the chemical make-up of water and many images showing the different water anvironments. There is a section about life in water, such as animals, plants, and plankton.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate">2008-10-03</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">277</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/16150070"> <span id="translatedtitle">Three-level hybrid vs. flat MPI on the <span class="hlt">Earth</span> Simulator: Parallel iterative solvers for finite-<span class="hlt">element</span> method</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">An efficient parallel iterative method for finite <span class="hlt">element</span> method has been developed for symmetric multiprocessor (SMP) cluster architectures with vector processors such as the <span class="hlt">Earth</span> Simulator. The method is based on a three-level hybrid parallel programming model, including message passing for inter-SMP node communication, loop directives by OpenMP for intra-SMP node parallelization and vectorization for each processing <span class="hlt">element</span> (PE). Simple</p> <div class="credits"> <p class="dwt_author">Kengo Nakajima</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">278</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/11750258"> <span id="translatedtitle">New Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We have derived new abundances of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> Pr, Dy, Tm, Yb, and Lu for the solar photosphere and for five very metal-poor, neutron-capture r-process-rich giant stars. The photospheric values for all five <span class="hlt">elements</span> are in good agreement with meteoritic abundances. For the low-metallicity sample, these abundances have been combined with new Ce abundances from a companion paper,</p> <div class="credits"> <p class="dwt_author">Christopher Sneden; James E. Lawler; John J. Cowan; Inese I. Ivans; Elizabeth A. Den Hartog; Inese I</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">279</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://spacemath.gsfc.nasa.gov/SMBooks/SMEarthV2.pdf#page=48"> <span id="translatedtitle"><span class="hlt">Earth</span>'s Atmosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This problem set is about the methods scientists use to compare the abundance of the different <span class="hlt">elements</span> in <span class="hlt">Earth</span>'s atmosphere. Answer key is provided. This is part of <span class="hlt">Earth</span> Math: A Brief Mathematical Guide to <span class="hlt">Earth</span> Science and Climate Change.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">280</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.staff.uni-mainz.de/zack/Konrad_Schmolke_etal_08.pdf"> <span id="translatedtitle">Combined thermodynamic and rare <span class="hlt">earth</span> <span class="hlt">element</span> modelling of garnet growth during subduction: Examples from ultrahigh-pressure eclogite of the Western Gneiss</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Combined thermodynamic and rare <span class="hlt">earth</span> <span class="hlt">element</span> modelling of garnet growth during subduction Keywords ultrahigh-pressure metamorphism garnet trace <span class="hlt">elements</span> Western Gneiss Region thermodynamic modeling garnets from the Western Gneiss Region (Norway). All investigated garnets show multiple growth zones</p> <div class="credits"> <p class="dwt_author">Zack, Thomas</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_13");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a 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href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a style="font-weight: bold;">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_16");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">281</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009JNuM..384..256C"> <span id="translatedtitle">Treatment of a waste salt delivered from an electrorefining process by an oxidative precipitation of the rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">For the reuse of a waste salt from an electrorefining process of a spent oxide fuel, a separation of rare <span class="hlt">earth</span> <span class="hlt">elements</span> by an oxidative precipitation in a LiCl-KCl molten salt was tested without using precipitate agents. From the results obtained from the thermochemical calculations by HSC Chemistry software, the most stable rare <span class="hlt">earth</span> compounds in the oxygen-used rare <span class="hlt">earth</span> chlorides system were oxychlorides (EuOCl, NdOCl, PrOCl) and oxides (CeO 2, PrO 2), which coincide well with results of the Gibbs free energy of the reaction. In this study, similar to the thermochemical results, regardless of the sparging time and molten salt temperature, oxychlorides and oxides were formed as a precipitant by a reaction with oxygen. The structure of the rare <span class="hlt">earth</span> precipitates was divided into two shapes: small cubic (oxide) and large plate-like (tetragonal) structures. The conversion efficiencies of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> to their molten salt-insoluble precipitates were increased with the sparging time and temperature, and Ce showed the best reactivity. In the conditions of 650 °C of the molten salt temperature and 420 min of the sparging time, the final conversion efficiencies were over 99.9% for all the investigated rare <span class="hlt">earth</span> chlorides.</p> <div class="credits"> <p class="dwt_author">Cho, Yung-Zun; Yang, Hee-Chul; Park, Gil-Ho; Lee, Han-Soo; Kim, In-Tae</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">282</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70009869"> <span id="translatedtitle">A chemical-spectrochemical method for the determination of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and thorium in cerium minerals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">In a combined chemical-spectrochemical procedure for quantitatively determining rare <span class="hlt">earth</span> <span class="hlt">elements</span> in cerium minerals, cerium is determined volumetrically, a total rare <span class="hlt">earths</span> plus thoria precipitate is separated chemically, the ceria content of the precipitate is raised to 80??0 percent by adding pure ceria, and the resulting mixture is analyzed for lanthanum, praseodymium, neodymium, samarium, gadolinium, yttrium, and thorium spectrochemically by means of the d.c. carbon arc. Spectral lines of singly ionized cerium are used as internal standard lines in the spectrochemical determination which is patterned after Fassel's procedure [1]. Results of testing the method with synthetic mixtures of rare <span class="hlt">earths</span> and with samples of chemically analyzed cerium minerals show that the coefficient of variation for a quadruplicate determination of any <span class="hlt">element</span> does not exceed 5??0 (excepting yttrium at concentrations less than 1 percent) and that the method is free of serious systematic error. ?? 1954.</p> <div class="credits"> <p class="dwt_author">Rose, H.J., Jr.; Murata, K.J.; Carron, M.K.</p> <p class="dwt_publisher"></p> <p class="publishDate">1954-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">283</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40699341"> <span id="translatedtitle">Strontium isotopes and rare <span class="hlt">earth</span> <span class="hlt">elements</span> as tracers of groundwater–lake water interactions, Lake Naivasha, Kenya</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Strontium isotope compositions and rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations are presented for groundwater and surface water samples collected from the Lake Naivasha watershed in the East African Rift, Kenya. The chief objective of the study is to test the suitability of REEs, in conjunction with Sr isotopes, as tools for investigating groundwater–lake water interactions. In general, the REE concentrations and</p> <div class="credits"> <p class="dwt_author">S. Bwire Ojiambo; W. Berry Lyons; Kathy A. Welch; Robert J. Poreda; Karen H. Johannesson</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">284</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.physics.ucf.edu/~rep/publications/JournalPubs2002/SandyGCA2002.pdf"> <span id="translatedtitle">PII S0016-7037(02)00888-8 EXAFS study of rare-<span class="hlt">earth</span> <span class="hlt">element</span> coordination in calcite</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">PII S0016-7037(02)00888-8 EXAFS study of rare-<span class="hlt">earth</span> <span class="hlt">element</span> coordination in calcite E. J. ELZINGA,1 , Sm3 , Dy3 , Yb3 ) coprecipitated with calcite in minor concentrations from room-temperature aqueous are longer than the Ca-O distance in calcite and longer than what is consistent with ionic radii sums</p> <div class="credits"> <p class="dwt_author">Peale, Robert E.</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">285</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40354769"> <span id="translatedtitle">Effect of some light rare <span class="hlt">earth</span> <span class="hlt">elements</span> on seed germination, seedling growth and antioxidant metabolism in Triticum durum</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) enriched fertilizers have been commonly used in China since the 1980s, thus inducing a growing concern about their environmental impact in agriculture. In this work, the effect of some light REEs nitrate mixture and La3+ nitrate on seed germination, seedling growth and antioxidant metabolism in Triticum durum was investigated with the aim of clarifying the potential</p> <div class="credits"> <p class="dwt_author">Luigi d’Aquino; Maria Concetta de Pinto; Luca Nardi; Massimo Morgana; Franca Tommasi</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">286</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/26215708"> <span id="translatedtitle">Distribution behavior of uranium, neptunium, rare-<span class="hlt">earth</span> <span class="hlt">elements</span> ( Y, La, Ce, Nd, Sm, Eu, Gd) and alkaline-<span class="hlt">earth</span> metals (Sr,Ba) between molten LiCl?KCI eutectic salt and liquid cadmium or bismuth</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Distribution coefficients of uranium neptunium, eight rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (Y, La, Ce, Pr, Nd, Sm, Eu and Gd) and two alkaline-<span class="hlt">earth</span> 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-<span class="hlt">earth</span> <span class="hlt">elements</span> to uranium or neptunium in the LiCl-KCl\\/Bi system were by one or two orders</p> <div class="credits"> <p class="dwt_author">M. Kurata; Y. Sakamura; T. Hijikata; K. Kinoshita</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">287</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014MinDe..49..987M"> <span id="translatedtitle">Hydrothermal transport and deposition of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> by fluorine-bearing aqueous liquids</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">New technologies, particularly those designed to address environmental concerns, have created a great demand for the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE), and focused considerable attention on the processes by which they are concentrated to economically exploitable levels in the <span class="hlt">Earth</span>'s crust. There is widespread agreement that hydrothermal fluids played an important role in the formation of the world's largest economic REE deposit, i.e. Bayan Obo, China. Until recently, many researchers have assumed that hydrothermal transport of the REE in fluorine-bearing ore-forming systems occurs mainly due to the formation of REE-fluoride complexes. Consequently, hydrothermal models for REE concentration have commonly involved depositional mechanisms based on saturation of the fluid with REE minerals due to destabilization of REE-fluoride complexes. Here, we demonstrate that these complexes are insignificant in REE transport, and that the above models are therefore flawed. The strong association of H+ and F- as HF° and low solubility of REE-F solids greatly limit transport of the REE as fluoride complexes. However, this limitation does not apply to REE-chloride complexes. Because of this, the high concentration of Cl- in the ore fluids, and the relatively high stability of REE-chloride complexes, the latter can transport appreciable concentrations of REE at low pH. The limitation also does not apply to sulphate complexes and in some fluids, the concentration of sulphate may be sufficient to transport significant concentrations of REE as sulphate complexes, particularly at weakly acidic pH. This article proposes new models for hydrothermal REE deposition based on the transport of the REE as chloride and sulphate complexes.</p> <div class="credits"> <p class="dwt_author">Migdisov, Art A.; Williams-Jones, A. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">288</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..1615804M"> <span id="translatedtitle">Rare-<span class="hlt">earth</span> <span class="hlt">elements</span> enrichment of Pacific seafloor sediments: the view from volcanic islands of Polynesia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) are key metals for «green» technologies such as energy saving lamps or permanent magnets used in, e.g., wind turbines, hard disk drives, portable phone or electric or hybrid vehicles. Since several years, world demand for these metals is therefore drastically increasing. The quasi-monopolistic position of China, which produces around 95 % of global REEs production, generates risks for the industries that depend on a secure supply of REEs. In response, countries are developing and diversifying their supply sources, with new mining projects located outside China and efforts in the area of REEs recycling. Most of these projects focus on deposits related to carbonatites and alkaline-peralkaline magmatism, which are generally enriched in light REEs (LREEs) compared to the heavy REEs (HREEs)-enriched deposits of the ion-adsorption types, located in southern China. However, a recent study revealed new valuable resources corresponding to seafloor sediments located in the south-eastern and north-central Pacific. The deep-sea mud described by these authors show a higher HREE/LREE ratio than ion-adsorption deposits, a feature which significantly increases their economic interest. The authors suggest mid-ocean ridge hydrothermal activity as an explanation to this anomalous enrichment. However, several contributions have documented considerable REEs enrichment in basalts and peridotitic xenoliths from French Polynesia. Several arguments have been exposed in favour of a supergene origin, with a short migration, suggesting that REEs were collected from weathered basalts. The Tahaa volcanic island (Sous-le-Vent Island, Society Archipelago, French Polynesia) is the first location where such enrichment has been described. New petrographic and mineralogical investigations confirm a supergene mobilization of this abnormal occurrence. REE-bearing minerals (mainly phosphates of the rhabdophane group) are primarily located within basalt vesicles but also in crack that cross-cut the calcite filling the vesicles or the volcanic glass. They are also closely associated with Ni-Mg bearing phyllosilicates, which appear to nucleate from alteration of olivine and clinopyroxenes. Further investigations are done to evidence and confirm an anterior magmatic enrichment. On the basis of these observations, we believe that the anomalous enrichment observed in seafloor sediments could derive from abnormally-rich provinces corresponding to aerial basaltic formations from oceanic islands primarily enriched during weathering processes (Melleton et al., 2014). Melleton et al. (2014). Rare-<span class="hlt">earth</span> <span class="hlt">elements</span> enrichment of Pacific sea-floor sediments: the view from volcanic islands of Polynesia. In preparation.</p> <div class="credits"> <p class="dwt_author">Melleton, Jérémie; Tuduri, Johann; Pourret, Olivier; Bailly, Laurent; Gisbert, Thierry</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">289</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014E%26PSL.398..101T"> <span id="translatedtitle">Efficient mobilization and fractionation of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> by aqueous fluids upon slab dehydration</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The characteristic REE fractionation pattern in arc magmas compared to MOR-basalts results from the selective mobilization of light rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (LREE) by slab-derived mobile components. However, the nature and composition of the slab flux, and the actual mechanisms responsible for the transfer of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REE) from the slab to the mantle wedge remain unclear. We present experimental data on the solubility of selected REE in ligand-bearing aqueous fluids and a hydrous haplogranitic melt at 2.6 GPa and 600-800 °C, spanning the conditions relevant to slab dehydration and melting. The solubilities of REE in aqueous fluids increase more than an order of magnitude with temperature increasing from 600 to 800 °C. Addition of ligands such as Cl-, F-, CO32-, SO42- in relatively small concentrations (0.3-1.5 m [mol/kg H2O]) has a pronounced effect further enhancing REE solubilities. Each ligand yields a characteristic REE pattern by preferential dissolution of either the light or the heavy REE. For example, the addition of NaCl to the aqueous fluids yields highly elevated LREE/HREE ratios (La/Yb=17.4±4.3), whereas the addition of fluoride and sulfate ligands significantly increases the solubility of all REE with moderate LREE/HREE fractionation (La/Yb?4). The addition of Na2CO3 results in preferential increase of HREE solubilities, and yields La/Yb ratio of 1.6±0.5 by flattening the moderately fractionated REE pattern seen in pure aqueous fluids. The solubilities in hydrous haplogranite melt are moderate in comparison to those observed in aqueous fluids and do not lead to pronounced REE fractionation. Therefore, REE can be effectively mobilized and fractionated by aqueous fluids, compared to felsic hydrous melts. Furthermore, the aqueous fluid chemistry has a major role in determining REE mobilities and fractionation upon slab dehydration in addition to the significant control exerted by temperature. Our results show that chloride-bearing slab-derived aqueous fluids have a significant contribution to the formation of REE-signatures in arc-magmas, especially at lower slab surface temperatures.</p> <div class="credits"> <p class="dwt_author">Tsay, A.; Zajacz, Z.; Sanchez-Valle, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">290</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1981E%26PSL..56..405W"> <span id="translatedtitle">Apatite/liquid partition coefficients for the rare <span class="hlt">earth</span> <span class="hlt">elements</span> and strontium</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Sixteen sets of apatite/liquid partition coefficients ( D ap/liq) for the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE; La, Sm, Dy, Lu) and six values for Sr were experimentally determined in natural systems ranging from basanite to granite. The apatite + melt (glass) assemblages were obtained from starting glasses artificially enriched in REE, Sr and fluorapatite components; these were run under dry and hydrous conditions of 7.5-20 kbar and 950-1120°C in a solid-media, piston-cylinder apparatus. An SEM-equipped electron microprobe was used for subsequent measurement of REE and Sr concentrations in coexisting apatites and quenched glasses. The resulting partition coefficient patterns resemble previously determined apatite phenocryst/groundmass concentration ratios in the following respects: (1) the rare <span class="hlt">earth</span> patterns are uniformly concave downward (i.e., the middle REE are more compatible in apatite than the light and heavy REE); (2) D REEap/liq is much higher for silicic melts than for basic ones; and (3) strontium (and therefore Eu 2+) is less concentrated by apatite than are the trivalent REE. The effects of both temperature and melt composition on D REEap/liq are systematic and pronounced. At 950°C, for example, a change in melt SiO 2 content from 50 to 68 wt.% causes the average REE partition coefficient to increase from ˜7 to ˜30. A 130°C increase in temperature, on the other hand, results in a two-fold decrease in D REEap/liq. Partitioning of Sr is insenstitive to changes in melt composition and temperature, and neither the Sr nor the REE partition coefficients appear to be affected by variations in pressure or H 2O content of the melt. The experimentally determined partition coefficients can be used not only in trace <span class="hlt">element</span> modelling, but also to distinguish apatite phenocrysts from xenocrysts in rocks. Reported apatite megacryst/host basalt REE concentration ratios [12], for example, are considerably higher than the equilibrium partition coefficients, which suggest that in this particular case the apatite is actually xenocrystic. A reversal experiment incorporated in our study yielded diffusion profiles of REE in apatite, from which we extracted a REE?Ca interdiffusion coefficient of 2-4×10 -14 cm 2/s at 1120°C. Extrapolated downward to crustal temperatures, this low value suggests that complete REE equilibrium between felsic partial melts and residual apatite is rarely established.</p> <div class="credits"> <p class="dwt_author">Watson, E. Bruce; Green, Trevor H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1981-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">291</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010GeCoA..74.6690T"> <span id="translatedtitle">Ligand extraction of rare <span class="hlt">earth</span> <span class="hlt">elements</span> from aquifer sediments: Implications for rare <span class="hlt">earth</span> <span class="hlt">element</span> complexation with organic matter in natural waters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The ability of organic matter as well as carbonate ions to extract rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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).</p> <div class="credits"> <p class="dwt_author">Tang, Jianwu; Johannesson, Karen H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">292</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2000P%26SS...48.1447H"> <span id="translatedtitle">Discovery of probable Tunguska cosmic body material: anomalies of platinum group <span class="hlt">elements</span> and rare-<span class="hlt">earth</span> <span class="hlt">elements</span> in peat near the Explosion Site /(1908)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Ten Sphagnum fuscum peat samples collected from different depths of a core including the layer affected by the 1908 Tunguska explosion in the Tunguska area of Central Siberia, Russia, were analyzed by ICP-MS to determine the concentrations of Pd, Rh, Ru, Co, REE, Y, Sr, and Sc. The analytical results indicate that the Pd and Rh concentrations in the event- and lower layers were 14.0-19.9, and 1.23-1.56 ppb, respectively, about 3-9 times and 3 times higher than the background values in the normal layers. In addition, the patterns of CI-chondrite-normalized REE in the event layers were much flatter than in the normal layers, and differed from those in the nearby traps. Hence, it can be inferred from the characteristics of the <span class="hlt">elemental</span> <span class="hlt">geochemistry</span> that the explosion was probably associated with extraterrestrial material, and which, most probably, was a small comet core the dust fraction of which was chemically similar to carbonaceous chondrites (CI). In terms of the Pd and REE excess fluxes in the explosion area, it can be estimated that the celestial body that exploded over Tunguska in 1908 weighed more than 10 6 t, corresponding to a radius of >60 m. If the celestial body was a comet, then its total mass was more than 2×10 7 t, and it had >160 m radius, and released an energy of >10 7 t TNT.</p> <div class="credits"> <p class="dwt_author">Hou, Q. L.; Kolesnikov, E. M.; Xie, L. W.; Zhou, M. F.; Sun, M.; Kolesnikova, N. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">293</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012E%26PSL.335..121P"> <span id="translatedtitle">Environmental changes across the Triassic-Jurassic boundary and coeval volcanism inferred from <span class="hlt">elemental</span> <span class="hlt">geochemistry</span> and mineralogy in the Kendlbachgraben section (Northern Calcareous Alps, Austria)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The end-Triassic extinction (ETE), one of the five largest Phanerozoic mass extinctions, is associated with rapid and severe environmental change, but existing data permit alternative models of causation. Volcanism in the Central Atlantic Magmatic Province (CAMP) has been proposed as the main trigger, but direct evidence for this linkage is scarce. To help constrain scenarios for the ETE and other Triassic-Jurassic boundary (TJB) events, we obtained a temporally highly resolved, multidisciplinary dataset from the Kendlbachgraben section in the Northern Calcareous Alps in Austria. The section belongs to the same paleogeographic unit (Eiberg Basin) and share similar stratigraphy with the recently selected base Jurassic Global Stratotype Section and Point at Kuhjoch. Micromineralogic study of the topmost bed of the Rhaetian Kössen Formation revealed pseudomorphs of altered, euhedral pyroxene and amphibole crystals. Their well-faceted morphology is consistent with their origin from distal mafic volcanic ash fallout. Spherical grains were also observed in the same bed, likely representing clay-altered volcanic glass. Clay minerals of this bed include low- to medium-charged smectite and Mg-vermiculite, both typical alteration products of mafic rocks. The same bed yielded a rare <span class="hlt">earth</span> <span class="hlt">element</span> pattern that differs from all other levels in an enrichment of heavy REEs, hinting at some minor contribution from mafic magmatic material. These features from a layer that was deposited very near to the TJB are interpreted as direct evidence of CAMP volcanism, coeval or immediately preceding the ETE and the initial negative carbon isotope anomaly. The kaolinite-dominated clay mineral spectrum of the overlying boundary mudstone records intensive weathering under hot and humid greenhouse conditions. Redox-sensitive minor and trace <span class="hlt">elements</span> do not support the development of widespread anoxia in the studied section. Although pyrite is common in several layers, framboid size indicates formation within a reductive zone, below the sediment/water interface, rather than in an anoxic water column. Our data provide a direct link between uppermost Triassic marine strata and CAMP-derived material. They support scenarios where CAMP volcanism induced climate and other environmental change, which in turn triggered the ETE and that is also reflected in the carbon isotope anomalies.</p> <div class="credits"> <p class="dwt_author">Pálfy, József; Zajzon, Norbert</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">294</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pds.jpl.nasa.gov/planets/choices/earth1.htm"> <span id="translatedtitle"><span class="hlt">Earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet <span class="hlt">Earth</span>. 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 <span class="hlt">Earth</span> 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.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">295</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JMEP...23.4251L"> <span id="translatedtitle">Effect of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> on Isothermal Transformation Kinetics in Si-Mn-Mo Bainite Steels</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Isothermal heat treatments to Si-Mn-Mo steel specimens were performed, and time-temperature-transformation curves (C-curves) were plotted by DIL805A/D differential dilatometer. The effect of rare <span class="hlt">earth</span> (RE) <span class="hlt">elements</span> on bainite transformation kinetics was systematically studied by adopting the empirical electron theory of solids and molecules, Johnson-Mehl-Avrami equation calculation, dilatometry, and metallography. Experimental results show that the addition of RE in Si-Mn-Mo bainite steels leads to the C-curves moving to bottom right and prolongs incubation period of bainite transformation. Moreover, RE addition increases the values of phase structure factors ( n A, F {C/D}) and activation energy of bainite transformation, inhibits the formation of granular bainite, and refines microstructures of bainitic ferrite and substructures. During the bainite transformation process, bainite transformation is delayed due to the drag effect, which is induced by the segregation of RE at the ferrite interphase and the retardation of Fe-C-RE (segregation units) on carbon diffusion.</p> <div class="credits"> <p class="dwt_author">Liang, Yilong; Yi, Yanliang; Long, Shaolei; Tan, Qibing</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">296</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JMEP..tmp..355L"> <span id="translatedtitle">Effect of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> on Isothermal Transformation Kinetics in Si-Mn-Mo Bainite Steels</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Isothermal heat treatments to Si-Mn-Mo steel specimens were performed, and time-temperature-transformation curves (C-curves) were plotted by DIL805A/D differential dilatometer. The effect of rare <span class="hlt">earth</span> (RE) <span class="hlt">elements</span> on bainite transformation kinetics was systematically studied by adopting the empirical electron theory of solids and molecules, Johnson-Mehl-Avrami equation calculation, dilatometry, and metallography. Experimental results show that the addition of RE in Si-Mn-Mo bainite steels leads to the C-curves moving to bottom right and prolongs incubation period of bainite transformation. Moreover, RE addition increases the values of phase structure factors (n A, F {C/D}) and activation energy of bainite transformation, inhibits the formation of granular bainite, and refines microstructures of bainitic ferrite and substructures. During the bainite transformation process, bainite transformation is delayed due to the drag effect, which is induced by the segregation of RE at the ferrite interphase and the retardation of Fe-C-RE (segregation units) on carbon diffusion.</p> <div class="credits"> <p class="dwt_author">Liang, Yilong; Yi, Yanliang; Long, Shaolei; Tan, Qibing</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">297</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24972173"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> distributions and fractionation in plankton from the northwestern Mediterranean Sea.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations were measured for the first time in plankton from the northwestern Mediterranean Sea. The REE concentrations in phytoplankton (60-200?m) were 5-15 times higher than those in four size fractions of zooplankton: 200-500?m, 500-1000?m, 1000-2000?m and >2000?m. The concentrations within these zooplankton fractions exhibited the same ranges with some variation attributed to differences in zooplankton taxonomy. The REE concentrations in plankton were poorly related to the reported REE concentrations of seawater, but they correlated well with the calculated REE(3+), concentrations especially with regard to middle REE (MREEs) and heavy REEs (HREEs). Plankton and seawater revealed different PAAS-normalised REE distributions, with the greatest differences observed in the light REEs. Interestingly, a comparison of PAAS-normalized sediment particles from the study of Fowler et al. (1992) showed concentrations of the same order of magnitude and a similar REE distribution without MREE enrichment. Based on this comparison, we propose a conceptual model that emphasizes the importance of biological scavenging of REEs (especially LREEs) in surface waters. PMID:24972173</p> <div class="credits"> <p class="dwt_author">Strady, Emilie; Kim, Intae; Radakovitch, Olivier; Kim, Guebuem</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">298</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AtmRe..94..300Z"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in an ice core from Mt. Everest: Seasonal variations and potential sources</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> (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.</p> <div class="credits"> <p class="dwt_author">Zhang, Qianggong; Kang, Shichang; Kaspari, Susan; Li, Chaoliu; Qin, Dahe; Mayewski, Paul A.; Hou, Shugui</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">299</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013MSMSE..21f5003F"> <span id="translatedtitle">Gupta potential for rare <span class="hlt">earth</span> <span class="hlt">elements</span> of the fcc phase: lanthanum and cerium</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The potential parameters for a Gupta-type many-body potential are fitted for the first two rare <span class="hlt">earth</span> <span class="hlt">elements</span>, La and Ce. The experimental cohesive energies, lattice parameters and elastic constants of ?-La and ?-Ce solids of the face-centered cubic (fcc) phase are well reproduced. The theoretical P-V curves, sound velocities and Debye temperatures of ?-La and ?-Ce solids are in reasonable agreement with experimental data. The vacancy formation energies and surface energies are also predicted. In particular, the phonon dispersion relationship and vibrational frequencies at high symmetric points within the first Brillouin zone from our potential are consistent with experimental ones. Molecular dynamics simulation are performed to determine the melting temperature of La and Ce solids as well as the radial distribution function of liquid La, which are also in line with experimental data. All these agreements indicate the validity of the current set of potential parameters. Thus, the Gupta potential developed here would be useful in future simulation of La, Ce solids and their alloys.</p> <div class="credits"> <p class="dwt_author">Fu, Jie; Zhao, Jijun</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">300</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009MMTA...40.2190K"> <span id="translatedtitle">Effects of Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> Additions on the Impression Creep Behavior of AZ91 Magnesium Alloy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The effects of 1, 2, and 3 wt pct rare <span class="hlt">earth</span> (RE) <span class="hlt">element</span> 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.</p> <div class="credits"> <p class="dwt_author">Kabirian, F.; Mahmudi, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-09-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_14");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span 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</span> </span> <a id="NextPageLink" onclick='return showDiv("page_17");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">301</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010MMTA...41.1973N"> <span id="translatedtitle">Effect of Ca and Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> on Impression Creep Properties of AZ91 Magnesium Alloy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Creep properties of AZ91 magnesium alloy and AZRC91 (AZ91 + 1 wt pct RE + 1.2 wt pct Ca) alloy were investigated using the impression creep method. It was shown that the creep properties of AZ91 alloy are significantly improved by adding Ca and rare <span class="hlt">earth</span> (RE) <span class="hlt">elements</span>. The improvement in creep resistance is mainly attributed to the reduction in the amount and continuity of eutectic ?(Mg17Al12) phase as well as the formation of new Al11RE3 and Al2Ca intermetallic compounds at interdendritic regions. It was found that the stress exponent of minimum creep rate, n, varies between 5.69 and 6 for AZ91 alloy and varies between 5.81 and 6.46 for AZRC91 alloy. Activation energies of 120.9 ± 8.9 kJ/mol and 100.6 ± 7.1 kJ/mol were obtained for AZ91 and AZRC91 alloys, respectively. It was shown that the lattice and pipe-diffusion-controlled dislocation climb are the dominant creep mechanisms for AZ91 and AZRC91 alloys, respectively. The constitutive equations, correlating the minimum creep rate with temperature and stress, were also developed for both alloys.</p> <div class="credits"> <p class="dwt_author">Nami, B.; Razavi, H.; Mirdamadi, S.; Shabestari, S. G.; Miresmaeili, S. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">302</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19770064910&hterms=Rare+earth+metals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528%2528Rare%2Bearth%2529%2Bmetals%2529"> <span id="translatedtitle">Composition and evolution of the eucrite parent body - Evidence from rare <span class="hlt">earth</span> <span class="hlt">elements</span>. [extraterrestrial basaltic melts</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Quantitative modeling of the evolution of rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) abundances in the eucrites, which are plagioclase-pigeonite basalt achondrites, indicates that the main group of eucrites (e.g., Juvinas) might have been produced by approximately 10% equilibrium partial melting of a single type of source region with initial REE abundances which were chondritic relative and absolute. Since the age of the eucrites is about equal to that of the solar system, extensive chemical differentiation of the eucrite parent body prior to the formation of eucrites seems unlikely. If homogeneous accretion is assumed, the bulk composition of the eucrite parent body can be estimated; two estimates are provided, representing different hypotheses as to the ratio of metal to olivine in the parent body. Since a large number of differentiated olivine meteorites, which would represent material from the interior of the parent body, have not been detected, the eucrite parent body is thought to be intact. It is suggested that the asteroid 4 Vesta is the eucrite parent body.</p> <div class="credits"> <p class="dwt_author">Consolmagno, G. J.; Drake, M. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1977-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">303</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24135922"> <span id="translatedtitle">State of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in different environmental components in mining areas of China.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">China has relatively abundant rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) reserves and will continue to be one of the major producers of REEs for the world market in the foreseeable future. However, due to the large scale of mining and refining activities, large amounts of REEs have been released to the surrounding environment and caused harmful effects on local residents. This paper summarizes the data about the contents and translocation of REEs in soils, waters, atmosphere, and plants in REE mining areas of China and discusses the characteristics of their forms, distribution, fractionation, and influencing factors. Obviously high concentrations of REEs with active and bioavailable forms are observed in all environmental media. The mobility and bioavailability of REEs are enhanced. The distribution patterns of REEs in soils and water bodies are all in line with their parent rocks. Significant fractionation phenomenon among individual members of REEs was found in soil-plant systems. However, limited knowledge was available for REEs in atmosphere. More studies focusing on the behavior of REEs in ambient air of REE mining areas in China are highly suggested. In addition, systematic study on the translocation and circulation of REEs in various media in REEs mining areas and their health risk assessment should be carried out. Standard analytical methods of REEs in environments need to be established, and more specific guideline values of REEs in foods should also be developed. PMID:24135922</p> <div class="credits"> <p class="dwt_author">Liang, Tao; Li, Kexin; Wang, Lingqing</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">304</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002GeCoA..66.1323D"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We present data on the composition of water from Lake Vanda, Antarctica. Vanda and other lakes in the McMurdo Dry Valleys of Antarctica are characterized by closed basins, permanent ice covers, and deep saline waters. The meromictic lakes provide model systems for the study of trace metal cycling owing to their pristine nature and the relative simplicity of their biogeochemical systems. Lake Vanda, in the Wright Valley, is supplied by a single input, the Onyx River, and has no output. Water input to the lake is balanced by sublimation of the nearly permanent ice cap that is broken only near the shoreline during the austral summer. The water column is characterized by an inverse thermal stratification of anoxic warm hypersaline water underlying cold oxic freshwater. Water collected under trace-<span class="hlt">element</span> clean conditions was analyzed for its dissolved and total rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations by inductively coupled plasma mass spectrometry. Depth profiles are characterized by low dissolved REE concentrations (La, Ce, <15 pM) in surface waters that increase slightly (La, 70 pM; Ce, 20 pM) with increasing depth to ˜55 m, the limit of the fresh oxic waters. Below this depth, a sharp increase in the concentrations of strictly trivalent REE (e.g., La, 5 nM) is observed, and a submaximum in redox sensitive Ce (2.6 nM) is found at 60- to 62-m depth. At a slightly deeper depth, a sharper Ce maximum is observed with concentrations exceeding 11 nM at a 67-m depth, immediately above the anoxic zone. The aquatic concentrations of REE reported here are ˜50-fold higher than previously reported for marine oxic/anoxic boundaries and are, to our knowledge, the highest ever observed at natural oxic/anoxic interfaces. REE maxima occur within stable and warm saline waters. All REE concentrations decrease sharply in the sulfidic bottom waters. The redox-cline in Lake Vanda is dominated by diffusional processes and vertical transport of dissolved species driven by concentration gradients. Furthermore, because the ultraoligotrophic nature of the lake limits the potential for organic phases to act as metal carriers, metal oxide coatings and sulfide phases appear to largely govern the distribution of trace <span class="hlt">elements</span>. We discuss REE cycling in relation to the roles of redox reactions and competitive scavenging onto Mn- and Fe-oxides coatings on clay sized particles in the upper oxic water column and their release by reductive dissolution near the anoxic/oxic interface.</p> <div class="credits"> <p class="dwt_author">De Carlo, Eric Heinen; Green, William J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">305</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011MinDe..46.1001C"> <span id="translatedtitle">Pyrite trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of mafic granulite xenoliths from Xikeer: implications for the source of Cu in the sediment-hosted mineralization in the northwestern Tarim Basin (Northwest China)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Xikeer mafic granulite xenoliths are hosted by a Cenozoic basanite sill (˜20 Ma) in the northwest Tarim Basin, northwest China. Sulfides, identified in these xenoliths consist mainly of pyrite. Two groups of pyrite (types A and B) can be distinguished based on petrography and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>, as determined by laser-ablation ICP-MS analysis. Type A pyrite is subhedral and in general has lower trace <span class="hlt">element</span> abundance than type B pyrite. Type B pyrite is fractured with ragged anhedral morphology and has extremely high Cu, Tl, Ni, and Co abundance. The low Co and Ni contents combined with a positive correlation between Cu, Cr, and Pb all indicate that the type A pyrite may have formed from a high-temperature magmatic hydrothermal fluid. In contrast, the Cu-, Tl-, Ni-, and Co-rich type B pyrite was probably formed in a relatively low-temperature basinal environment. The Cu mineralization at Xikeer can be explained when Cu, Tl, Ni, and Co were leached from the intruded basanites and subsequently enriched in circulating basin brines. Such enrichment of Cu in basin brines could provide an important Cu source for the Cu mineralization in the Xikeer district and other Cenozoic sub-basins in the Tarim Basin.</p> <div class="credits"> <p class="dwt_author">Chen, Huayong; Tian, Wei; Falloon, Trevor J.; Chen, Mimi</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">306</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/22066167"> <span id="translatedtitle">Microstructure and properties of 17-4PH steel plasma nitrocarburized with a carrier gas containing rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The effect of rare <span class="hlt">earth</span> 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 <span class="hlt">earth</span> <span class="hlt">elements</span> 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 <span class="hlt">earth</span> addition is caused by improvement in microstructure and change in the phase proportion of the nitrocarburized layer.</p> <div class="credits"> <p class="dwt_author">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)</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">307</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/355671"> <span id="translatedtitle">Yttrium and rare <span class="hlt">earth</span> <span class="hlt">elements</span> in fluids from various deep-sea hydrothermal systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) and yttrium (Y) concentrations were measured in fluids collected from deep-sea hydrothermal systems including the Mid-Atlantic Ridge (MAR), i.e., Menez Gwen, Lucky Strike, TAG, and Snakepit; the East Pacific Rise (EPR), i.e., 13{degree}N and 17--19{degree}S; and the Lau (Vai Lili) and Manus (Vienna Woods, PacManus, Desmos) Back-arc Basins (BAB) in the South-West Pacific. In most fluids, Y is trivalent and behaves like Ho. Chondrite normalized Y-REE (Y-REE{sub N}) concentrations of fluids from MAR, EPR, and two BAB sites, i.e., Vai Lili and Vienna Woods, showed common patterns with LREE enrichment and positive Eu anomalies. REE analysis of plagioclase collected at Lucky Strike strengthens the idea that fluid REE contents, are controlled by plagioclase phenocrysts. Other processes, however, such as REE complexation by ligands (Cl{sup {minus}}, F{sup {minus}}, So{sub 4}{sup 2{minus}}), secondary phase precipitation, and phase separation modify REE distributions in deep-sea hydrothermal fluids. REE speciation calculations suggest that aqueous REE are mainly complexed by Cl{sup {minus}} ions in hot acidic fluids from deep-sea hydrothermal systems. REE concentrations in the fluid phases are, therefore, influenced by temperature, pH, and duration of rock-fluid interaction. Unusual Y-REE{sub N} patterns found in the PacManus fluids are characterized by depleted LREE and a positive Eu anomaly. The Demos fluid sample shows a flat Y-REE{sub N} pattern, which increases regularly from LREE to HREE with no Eu anomaly. These Manus Basin fluids also have an unusual major <span class="hlt">element</span> chemistry with relatively high Mg, So{sub 4}, H{sub 2}S, and F contents, which may be due to the incorporation of magmatic fluids into heated seawater during hydrothermal circulation. REE distribution in PacManus fluids may stem from a subseafloor barite precipitation and the REE in Demos fluids are likely influenced by the presence of sulfate ions.</p> <div class="credits"> <p class="dwt_author">Douville, E. [Univ. Bretagne Occidentale, Brest (France). Dept. de Chimie] [Univ. Bretagne Occidentale, Brest (France). Dept. de Chimie; [IFREMER Centre de Brest, Plouzane (France); Appriou, P. [Univ. Bretagne Occidentale, Brest (France)] [Univ. Bretagne Occidentale, Brest (France); Bienvenu, P. [CEA Cadarache, Saint Paul Lez Durance (France). Lab. d`Analyses Radiochimiques et Chimiques] [CEA Cadarache, Saint Paul Lez Durance (France). Lab. d`Analyses Radiochimiques et Chimiques; Charlou, J.L.; Donval, J.P.; Fouquet, Y. [IFREMER Centre de Brest, Plouzane (France)] [IFREMER Centre de Brest, Plouzane (France); Gamo, Toshitaka [Univ. of Tokyo, Nakano, Tokyo (Japan). Ocean Research Inst.] [Univ. of Tokyo, Nakano, Tokyo (Japan). Ocean Research Inst.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">308</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.H21C0836M"> <span id="translatedtitle">Riparian Dendrochemistry: Detecting Rare-<span class="hlt">Earth</span> <span class="hlt">Elements</span> in Trees along an Effluent- Dominated Desert River</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This research documents spatial and temporal patterns of effluent uptake by riparian trees through development of a new and innovative application for dendrochronology, specifically dendrochemistry. The rare-<span class="hlt">earth</span> <span class="hlt">element</span> (REE) gadolinium (Gd), is a known micro-pollutant that enters streams from wastewater treatment plants. Gd was first used in select medical procedures in 1988 and subsequently discharged via treatment plants into waterways. Trees uptake Gd but do not utilize it, thereby providing a specific presence/absence date stamp in tree rings and making it an ideal marker of effluent water use by trees. Results from this study along an effluent-dominated portion of the Santa Cruz River in southeastern Arizona, show elevated levels of Gd in surface flows and the presence of Gd in cottonwood (Populus fremontii) growth rings. The first indication of Gd in tree rings occurred around 1988, and concentrations increased through 2000 followed by a sharp decline from 2001-2005. These dendrochronological results suggest that a clogging layer prevented effluent from infiltrating and recharging groundwater tables during the 2001-2005 drought period, thus reducing concentrations of Gd and other REEs in the groundwater tables. Since riparian trees depend on groundwater for some or all of their water needs, a reduction of Gd in tree rings indicates reduced effluent concentrations in groundwater and therefore a limited connection between the river and the groundwater due to a clogging layer. The impact of effluent quality on the chemical composition of tree rings is a useful monitoring tool to evaluate temporal patterns of surface water quality, the extent of surface and groundwater interactions, and the influence of effluent on riparian ecosystems.</p> <div class="credits"> <p class="dwt_author">McCoy, A. L.; Sheppard, P. R.; Meixner, T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">309</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014GeCoA.126..455H"> <span id="translatedtitle">Biogeochemical implications from dissolved rare <span class="hlt">earth</span> <span class="hlt">element</span> and Nd isotope distributions in the Gulf of Alaska</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Dissolved rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations and Nd isotope compositions were measured for surface waters and full water column profiles of the Gulf of Alaska (GoA), and compared to water mass properties and circulation in order to better understand the mechanisms controlling the input and transport of REEs in the ocean. The REEs display a typical open-ocean range of concentrations (i.e., La: 12-66 pM; Lu: 0.2-2.5 pM) and depth distributions (i.e., surface ocean depletion and enrichment with water depth). Nd isotope signatures are highly radiogenic, as expected for the North Pacific margin (ranging from -3.8 to +0.2 ?Nd). The most radiogenic values were found in the coastal waters but also in the cores of eddies, indicating efficient export of REEs from the margins and across the mixed layer. This is the first time that distinct Nd isotope distributions in near surface waters can be directly assigned to offshore eddy transport. A distinct mid-depth (˜2200 m) Nd isotope signal was found that most likely reflects advection of a water mass that formed through past down-welling in the Northern Pacific. Subsurface Nd isotope compositions appear to behave conservatively and can be explained through a REE distribution model proposed here. This model is based on multivariate analysis of the REEs and invokes two distinct “pools” of dissolved REEs: a “passive pool” complexed by carbonate ions, and a “bio-reactive pool” that is microbially manipulated. The latter “pool” is only significant in the upper water column and most likely reflects the indirect effects of microbial cycling of iron. Our model of the open ocean REE distribution contributes to explaining the conservative nature of Nd isotopes and provides a mechanism linking surface ocean and pore water REE dynamics.</p> <div class="credits"> <p class="dwt_author">Haley, Brian A.; Frank, Martin; Hathorne, Ed; Pisias, Nick</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">310</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20110012866&hterms=Paleoclimatology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DPaleoclimatology"> <span id="translatedtitle">The Formation of Sulfate and <span class="hlt">Elemental</span> Sulfur Aerosols Under Varying Laboratory Conditions: Implications for Early <span class="hlt">Earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45 x 10(exp 9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO2) by UV light with lambda < 220 nm has been shown in models and some initial laboratory studies to create a S-MIF; however, sulfur must leave the atmosphere in at least two chemically different forms to preserve any S-MIF signature. Two commonly cited examples of chemically different sulfur species that could have exited the atmosphere are <span class="hlt">elemental</span> sulfur (S8) and sulfuric acid (H2S04) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO2 either photolyzes at wavelengths from 115 to 400 nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H2) or methane (CH4), increased the formation of S8. With UV photolysis, formation of S8 aerosols is highly dependent on the initial SO2 pressure; and S8 is only formed at a 2% SO2 mixing ratio and greater in the absence of a reductant, and at a 0.2% SO2 mixing ratio and greater in the presence of 1000 ppmv CH4. We also found that organosulfur compounds are formed from the photolysis of CH4 and moderate amounts of SO2, The implications for sulfur aerosols on early <span class="hlt">Earth</span> are discussed.</p> <div class="credits"> <p class="dwt_author">DeWitt, H. Langley; Hasenkopf, Christa A.; Trainer, Melissa G.; Farmer, Delphine K.; Jimenez, Jose L.; McKay, Christopher P.; Toon, Owen B.; Tolbert, Margaret A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">311</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012GeCoA..89....1M"> <span id="translatedtitle">Aluminium competitive effect on rare <span class="hlt">earth</span> <span class="hlt">elements</span> binding to humic acid</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Competitive mechanisms between rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) and aluminium for humic acid (HA) binding were investigated by combining laboratory experiments and modeling to evaluate the effect of Al on REE-HA complexation. Results indicates that Al3+ competes more efficiently with heavy REE (HREE) than with light REE (LREE) in acidic (pH = 3) and low REE/HA concentration ratio conditions providing evidence for the Al high affinity for the few HA multidentate sites. Under higher pH - 5 to 6 - and high REE/HA conditions, Al is more competitive for LREE suggesting that Al is bound to HA carboxylic rather than phenolic sites. PHREEQC/Model VI Al-HA binding parameters were optimized to simulate precisely both Al binding to HA and Al competitive effect on REE binding to HA. REE-HA binding pattern is satisfactorily simulated for the whole experimental conditions by the ?LK1A optimization (i.e. ?LK1A controls the distribution width of log K around log KMA). The present study provides fundamental knowledge on Al binding mechanisms to HA. Aluminium competitive effect on other cations binding to HA depends clearly on its affinity for carboxylic, phenolic or chelate ligands, which is pH dependent. Under circumneutral pH such as in natural waters, Al should lead to LREE-depleted patterns since Al is expected to be bound to weak HA carboxylic groups. As deduced from the behavior of Al species, other potential competitor cations are expected to have their own competitive effect on REE-HA binding. Therefore, in order to reliably understand and model REE-HA patterns in natural waters, a precise knowledge of the exact behavior of the different REE competitor cations is required. Finally, this study highlights the ability of the REE to be used as a "speciation probe" to precisely describe cation interactions with HA as here evidenced for Al.</p> <div class="credits"> <p class="dwt_author">Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline; Bouhnik-Le Coz, Martine</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">312</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014MinDe..49..967H"> <span id="translatedtitle">The rare <span class="hlt">earth</span> <span class="hlt">element</span> potential of kaolin deposits in the Bohemian Massif (Czech Republic, Austria)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Four kaolin deposits in the Bohemian Massif were studied in order to assess the potential for the recovery of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) as by-products from the residue after extraction and refining of the raw kaolin. The behaviour of REE + Y during kaolinitization was found to be largely a function of pre-alteration mineralogy. In the examples studied, i.e. granite-derived deposits of Kriechbaum (Austria) and Boži?any, and arkose-derived deposits of Kazn?jov and Podbo?any (all Czech Republic), the REE + Y are predominantly hosted by monazite which has remained unaffected by kaolinitization. The overall REE + Y content of the variably kaolinitized rocks is strongly dependent on their genesis. While ion adsorption plays only a minor role in the concentration of REE + Y in the studied kaolinitized rocks, the processing and refining of the raw kaolin leads to residues that are enriched in REE + Y by a factor of up to 40. The use of a magnetic separator and a hydrocyclone in the processing of the raw material can yield REE + Y contents of as much as 0.77 wt%. Although this value compares well with the REE + Y concentration in some potentially economic REE + Y projects elsewhere, the overall tonnage of the (REE + Y)-enriched residue is by far not sufficient to consider economic extraction of REE + Y as by-product. Our results are most probably applicable also to other kaolin deposits derived from the weathering of Hercynian basement granites elsewhere (e.g. in Saxonia and Bavaria, Germany). Overall, the potential for REE + Y production as by-product from kaolin mining has to be regarded as minimal.</p> <div class="credits"> <p class="dwt_author">Höhn, S.; Frimmel, H. E.; Pašava, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">313</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70018287"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> concentrations in geological and synthetic samples using synchrotron X-ray fluorescence analysis</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">The concentrations of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in specific mineral grains from the Bayan Obo ore deposit and synthetic high-silica glass samples have been measured by synchrotron X-ray fluorescence (SXRF) analysis using excitation of the REE K lines between 33 and 63 keV. Because SXRF, a nondestructive analytical technique, has much lower minimum detection limits (MDLs) for REEs, it is an important device that extends the in situ analytical capability of electron probe microanalysis (EPMA). The distribution of trace amounts of REEs in common rock-forming minerals, as well as in REE minerals and minerals having minor quantities of REEs, can be analyzed with SXRF. Synchrotron radiation from a bending magnet and a wiggler source at the National Synchrotron Light Source, Brookhaven National Laboratory, was used to excite the REEs. MDLs of 6 ppm (La) to 26 ppm (Lu) for 3600 s in 60-??m-thick standard samples were obtained with a 25-??m diameter wiggler beam. The MDLs for the light REEs were a factor of 10-20 lower than the MDLs obtained with a bending magnet beam. The SXRF REE concentrations in mineral grains greater than 25 ??m compared favorably with measurements using EPMA. Because EPMA offered REE MDLs as low as several hundred ppm, the comparison was limited to the abundant light REEs (La, Ce, Pr, Nd). For trace values of medium and heavy REEs, the SXRF concentrations were in good agreement with measurements using instrumental neutron activation analysis (INAA), a bulk analysis technique. ?? 1993.</p> <div class="credits"> <p class="dwt_author">Chen, J.R.; Chao, E.C.T.; Back, J.M.; Minkin, J.A.; Rivers, M.L.; Sutton, S.R.; Cygan, G.L.; Grossman, J.N.; Reed, M.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">314</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.imwa.info/geochemistry/Chapters/Chapter07.pdf"> <span id="translatedtitle">Trace <span class="hlt">Elements</span> in Igneous Processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This site is a chapter from a book on <span class="hlt">geochemistry</span> by Dr. W. M. White used in a <span class="hlt">geochemistry</span> course at Cornell University. All aspects of trace <span class="hlt">elements</span> are discussed, including the definition, distribution, and behavior of trace <span class="hlt">elements</span>, as well as their importance in igneous petrology. Figures accompany the text.</p> <div class="credits"> <p class="dwt_author">William M. White</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">315</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/20995431"> <span id="translatedtitle">Experimental Investigation of Evaporation Behavior of Polonium and Rare-<span class="hlt">Earth</span> <span class="hlt">Elements</span> in Lead-Bismuth Eutectic Pool</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Equilibrium evaporation behavior was experimentally investigated for polonium ({sup 210}Po) in liquid lead-bismuth eutectic (LBE) and for rare-<span class="hlt">earth</span> <span class="hlt">elements</span> gadolinium (Gd) and europium (Eu) in LBE to understand and clarify the transfer behavior of toxic impurities from LBE coolant to a gas phase. The experiments utilized the 'transpiration method' in which saturated vapor in an isothermal evaporation pot was transported by inert carrier gas and collected outside of the pot. While the previous paper ICONE12-49111 has already reported the evaporation behavior of LBE and of tellurium in LBE, this paper summarizes the outlines and the results of experiments for important impurity materials {sup 210}Po and rare-<span class="hlt">earth</span> <span class="hlt">elements</span> which are accumulated in liquid LBE as activation products and spallation products. In the experiments for rare-<span class="hlt">earth</span> <span class="hlt">elements</span>, non-radioactive isotope was used. The LBE pool is about 330-670 g in weight and has a surface area of 4 cm x 14 cm. {sup 210}Po experiments were carried out with a smaller test apparatus and radioactive {sup 210}Po produced through neutron irradiation of LBE in the Japan Materials Testing Reactor (JMTR). We obtained fundamental and instructive evaporation data such as vapor concentration, partial vapor pressure of {sup 210}Po in the gas phase, and gas-liquid equilibrium partition coefficients of the impurities in LBE under the temperature condition between 450 and 750 deg. C. The {sup 210}Po test revealed that Po had characteristics to be retained in LBE but was still more volatile than LBE solvent. A part of Eu tests implied high volatility of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> comparable to that of Po. This tendency is possibly related to the local enrichment of the solute near the pool surface and needs to be investigated more. These results are useful and indispensable for the evaluation of radioactive materials transfer to the gas phase in LBE-cooled nuclear systems. (authors)</p> <div class="credits"> <p class="dwt_author">Shuji Ohno; Shinya Miyahara; Yuji Kurata [Japan Atomic Energy Agency (Japan); Ryoei Katsura [Nippon Nuclear Fuel Development Co., Ltd. (Japan); Shigeru Yoshida [KAKEN Co., Ltd. (Japan)</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">316</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/9464m1v273794083.pdf"> <span id="translatedtitle">Species and distribution of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Baotou section of the Yellow River in China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper analyses the contents and species distributions of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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</p> <div class="credits"> <p class="dwt_author">Jiang He; Chang-Wei Lü; Hong-Xi Xue; Ying Liang; Saruli Bai; Ying Sun; Li-Li Shen; Na Mi; Qing-Yun Fan</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">317</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57888316"> <span id="translatedtitle">Preparation and Photocatalysis Properties of Bacterial Cellulose\\/TiO2 Composite Membrane Doped with Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Bacterial cellulose (BC) was chosen as a support for nanometer titanium dioxide (TiO2) particles due to its superfine network structure. The composite membrane of TiO2\\/BC doped with rare <span class="hlt">earth</span> <span class="hlt">elements</span> was prepared by a sol-gel method using tetraisopropyl titanate as starting material. Photocatalysis properties of this composite membrane were estimated by using methyl orange as a degradation agent. X-ray fluorescence</p> <div class="credits"> <p class="dwt_author">Xiuju Zhang; Wenbin Chen; Zhidan Lin; Jia Yao; Shaozao Tan</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">318</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://anquetil.colorado.edu/~archie/publications/Zhong_etal_2003.pdf"> <span id="translatedtitle">Three-dimensional finite-<span class="hlt">element</span> modelling of <span class="hlt">Earth</span>'s viscoelastic deformation: effects of lateral variations in lithospheric thickness</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We have developed a 3-D spherical finite-<span class="hlt">element</span> model to study the dynamic response to surface loads of a self-gravitating and incompressible <span class="hlt">Earth</span> with 3-D viscoelastic structure. We have forced our model with the ICE-3G deglaciation history of Tushingham & Peltier to study the effects of laterally varying lithospheric thickness on observations of post-glacial rebound (PGR). The laterally varying lithospheric thicknesses</p> <div class="credits"> <p class="dwt_author">Shijie Zhong; Archie Paulson; John Wahr</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">319</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/6842653"> <span id="translatedtitle">A model for continental crust genesis by arc accretion: rare <span class="hlt">earth</span> <span class="hlt">element</span> evidence from the Irish Caledonides</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The formation of continental crust is a complex problem with a paradox at its center: continental material is believed to form by arc magmatism, a model that does not reconcile the bulk mafic and light rare <span class="hlt">earth</span> <span class="hlt">element</span> (LREE)-depleted composition of intra-oceanic arcs with the andesitic, LREE-enriched composition of continents. We present evidence supporting an arc origin for continental crust</p> <div class="credits"> <p class="dwt_author">Amy E. Draut; Peter D. Clift; Robyn E. Hannigan; Graham Layne; Nobumichi Shimizu</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">320</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.sci.uidaho.edu/swood/pdf/papers/fisher_creek_ree.pdf"> <span id="translatedtitle">Diel behavior of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in a mountain stream with acidic to neutral pH</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Diel (24-h) changes in concentrations of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave</p> <div class="credits"> <p class="dwt_author">Christopher H. Gammons; Scott A. Wood; David A. Nimick</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_15");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">321</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41132973"> <span id="translatedtitle">Distribution of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and neodymium isotopes in settling particulate material of the tropical Atlantic Ocean (EUMELI site)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We analysed rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) concentrations and Nd isotopic ratios of large sinking particles to investigate chemical scavenging processes. The sinking particles were collected with time-series sediment traps at 2500 m at two sites in the tropical northeastern Atlantic: a mesotrophic site (M-site: 18°N, 21°W) and an oligotrophic site (O-site: 21°N, 31°W). Shalenormalized REE patterns of the trapped material</p> <div class="credits"> <p class="dwt_author">K. Tachikawa; C. Handel; B. Dupre</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">322</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/14830761"> <span id="translatedtitle">Rare-<span class="hlt">earth</span> <span class="hlt">elements</span> and uranium in high-temperature solutions from East Pacific Rise hydrothermal vent field (13 °N)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The mobility of rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (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</p> <div class="credits"> <p class="dwt_author">A. Michard; F. Albarède; G. Michard; J. F. Minster; J. L. Charlou</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">323</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.V43D..03B"> <span id="translatedtitle">Hf and Nd Isotope Evidence for Production of an Incompatible Trace <span class="hlt">Element</span> Enriched Crustal Reservoir in Early <span class="hlt">Earth</span> (Invited)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The final significant stage of accretion of the <span class="hlt">Earth</span> was likely a collision between proto-<span class="hlt">Earth</span> 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 <span class="hlt">Earth</span>, with a consequent magma ocean (MO). During subsequent cooling, the <span class="hlt">Earth</span> 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 <span class="hlt">elements</span> (ITE) in sufficient quantities to contain a significant amount of the bulk <span class="hlt">Earth’s</span> budget for rare <span class="hlt">earth</span> <span class="hlt">elements</span>, 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 <span class="hlt">Earth</span> 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 <span class="hlt">Earth’s</span> 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 <span class="hlt">Earth’s</span> surface over the first 2 Ga of <span class="hlt">Earth</span> 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 <span class="hlt">Earth</span>, 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.</p> <div class="credits"> <p class="dwt_author">Brandon, A. D.; Debaille, V.; Lapen, T. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">324</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013Litho.172..192C"> <span id="translatedtitle">Mineral chemistry of Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> (REE) mineralization, Browns Ranges, Western Australia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">‘Green energy futures’ are driving unprecedented demand for Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> (REE), underpinning significant exploration activity worldwide. Understanding how economic REE concentrations form is critical for development of exploration models. REE mineralisation in the Browns Ranges, Gordon Downs Region, Western Australia, comprises xenotime-dominant mineralisation hosted within Archaean to Palaeoproterozoic metasedimentary units (Browns Range Metamorphics). Mineralogical, petrographic and mineral-chemical investigation, including trace <span class="hlt">element</span> analysis by Laser-Ablation Inductively-Coupled Plasma Mass Spectroscopy, gives insights into the mineralogical distribution and partitioning of REE, and also provides evidence for the genetic evolution of the Browns Range REE mineralisation via a succession of hydrothermal processes. Two main REE-bearing minerals are identified: xenotime [(Y,REE)PO4], which is HREE selective; and subordinate florencite [(REEAl3(PO4)2(OH)6] which is LREE selective. Two morphological generations of xenotime are recognised; compositions are however consistent. Xenotime contains Dy (up to 6.5 wt.%), Er (up to 4.35 wt.%), Gd (up to 7.56 wt.%), Yb (up to 4.65 wt.%) and Y (up to 43.3 wt.%). Laser Ablation ICP-MS <span class="hlt">element</span> mapping revealed a subtle compositional zoning in some xenotime grains. LREE appear concentrated in the grain cores or closest to the initial point of growth whereas HREE, particularly Tm, Yb and Lu, are highest at the outer margins of the grains. The HREE enrichment at the outer margins is mimicked by As, Sc, V, Sr, U, Th and radiogenic Pb. Florencite is commonly zoned and contains Ce (up to 11.54 wt.%), Nd (up to 10.05 wt.%) and La (up to 5.40 wt.%) and is also notably enriched in Sr (up to 11.63 wt.%) and Ca. Zircon (which is not a significant contributor of REEs overall due to its low abundance in the rocks) is also enriched in REE (up to 13 wt.% ?REE) and is the principal host of Sc (up to 0.8 wt.%). Early, coarse euhedral xenotime has undergone fracturing, partial breakdown and replacement by florencite. Second generation xenotime occurs as abundant small blades commonly associated with acicular hematite. Mineralization is attributed to percolation of a volatile-rich, acidic fluid, possibly granite-derived, through porous arkose units. Late hematite may suggest mixing with meteoric water and subsequent oxidation. Field observations suggest that faults acted as fluid conduits and that brecciation, possibly associated with release of volatiles from the fluid, occurred along these faults. The data provide valuable constraints on chemical compositional trends in xenotime and coexisting minerals. Given the current surge in exploration for REE, this information will assist in the development of exploration models for comparable terranes.</p> <div class="credits"> <p class="dwt_author">Cook, Nigel J.; Ciobanu, Cristiana L.; O'Rielly, Daniel; Wilson, Robin; Das, Kevin; Wade, Benjamin</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">325</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/sir20105070J"> <span id="translatedtitle">A deposit model for carbonatite and peralkaline intrusion-related rare <span class="hlt">earth</span> <span class="hlt">element</span> deposits: Chapter J in Mineral deposit models for resource assessment</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare <span class="hlt">earth</span> <span class="hlt">elements</span>. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other <span class="hlt">elements</span> enriched in these deposits include manganese, strontium, tantalum, thorium, vanadium, and uranium. Carbonatite and peralkaline intrusion-related rare <span class="hlt">earth</span> <span class="hlt">element</span> deposits are presented together in this report because of the spatial, and potentially genetic, association between carbonatite and alkaline rocks. Although these rock types occur together at many locations, carbonatite and peralkaline intrusion-related rare <span class="hlt">earth</span> <span class="hlt">element</span> deposits are not generally found together. Carbonatite hosted rare <span class="hlt">earth</span> <span class="hlt">element</span> deposits are found throughout the world, but currently only five are being mined for rare <span class="hlt">earth</span> <span class="hlt">elements</span>: Bayan Obo, Daluxiang, Maoniuping, and Weishan deposits in China and the Mountain Pass deposit in California, United States. These deposits are enriched in light rare <span class="hlt">earth</span> <span class="hlt">elements</span>, including lanthanum, cerium, praseodynium, and neodynium. The principal rare <span class="hlt">earth</span> <span class="hlt">element</span>-minerals associated with carbonatites are fluocarbonates (bastnäsite, parisite, and synchysite), hydrated carbonates (ancylite), and phosphates (monazite) with bastnäsite being the primary ore mineral. Calcite and dolomite are the primary gangue minerals. At present, the only rare <span class="hlt">earth</span> <span class="hlt">element</span> production from a peralkaline intrusion-related deposit is as a byproduct commodity at the Lovozero deposit in Russia. Important rare <span class="hlt">earth</span> <span class="hlt">element</span> minerals found in various deposits include apatite, eudialyte, loparite, gittinsite, xenotime, gadolinite, monazite, bastnäsite, kainosite, mosandrite, britholite, allanite, fergusonite, and zircon, and these minerals tend to be enriched in heavy rare <span class="hlt">earth</span> <span class="hlt">elements</span>. Carbonatite and alkaline intrusive complexes are derived from partial melts of mantle material, and neodymium isotopic data are consistent with the rare <span class="hlt">earth</span> <span class="hlt">elements</span> being derived from the parental magma. Deposits and these associated rock types tend to occur within stable continental tectonic units, in areas defined as shields, cratons, and crystalline blocks; they are generally associated with intracontinental rift and fault systems. Protracted fractional crystallization of the magma leads to enrichment in rare <span class="hlt">earth</span> <span class="hlt">elements</span> and other incompatible <span class="hlt">elements</span>. Rare <span class="hlt">earth</span> <span class="hlt">element</span> mineralization associated with carbonatites can occur as either primary mineral phases or as mineralization associated with late stage orthomagmatic fluids. Rare <span class="hlt">earth</span> <span class="hlt">element</span> mineralization associated with alkaline intrusive complexes may occur as primary phases in magmatic layered complexes or as late-stage dikes and veins. The greatest environmental challenges associated with carbonatite and peralkaline intrusion-related rare <span class="hlt">earth</span> <span class="hlt">element</span> deposits center on the associated uranium and thorium. Considerable uncertainty exists around the toxicity of rare <span class="hlt">earth</span> <span class="hlt">elements</span> and warrants further investigation. The acid-generating potential of carbonatites and peralkaline intrusion-related deposits is low due to the dominance of carbonate minerals in carbonatite deposits, the presence of feldspars and minor calcite within the alkaline intrusion deposits, and only minor quantities of potentially acid-generating sulfides. Therefore, acid-drainage issues are not likely to be a major concern associated with these deposits. Uranium has the potential to be recovered as a byproduct, which would mitigate some of its environmental effects. However, thorium will likely remain a waste-stream product that will require management since progress is not being made towards the development of thorium-based nuclear reactors in the United States or other large scale commercial uses. Because some deposits are rich in fluorine and beryllium, these <span class="hlt">elements</span> may be of environmental concern in certain locations.</p> <div class="credits"> <p class="dwt_author">Verplanck, Philip L.; Van Gosen, Bradley S.; Seal, Robert R., II; McCafferty, Anne E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">326</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19940030959&hterms=Anatomy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnatomy"> <span id="translatedtitle">Anatomy of a cluster IDP. Part 2: Noble gas abundances, trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>, isotopic abundances, and trace organic chemistry of several fragments from L2008#5</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The topics discussed include the following: noble gas content and release temperatures; trace <span class="hlt">element</span> abundances; heating summary of cluster fragments; isotopic measurements; and trace organic chemistry.</p> <div class="credits"> <p class="dwt_author">Thomas, K. L.; Clemett, S. J.; Flynn, G. J.; Keller, L. P.; Mckay, David S.; Messenger, S.; Nier, A. O.; Schlutter, D. J.; Sutton, S. R.; Walker, R. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">327</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012amos.confE..46B"> <span id="translatedtitle">Improving Low-<span class="hlt">Earth</span> Orbit Predictions Using Two-line <span class="hlt">Element</span> Data with Bias Correction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In this paper we present results from our orbit prediction study using the publicly available Two-Line <span class="hlt">Element</span> (TLE) sets. The method presented here is similar to that introduced by Levit and Marshall; however, we also consider the non-spherical low-<span class="hlt">Earth</span> orbit satellites Grace A and Grace B. The method uses 10 days of TLE data which is interpolated using SGP4. A state vector is generated every 10 minutes in the orbit determination (OD) period. These generated states are subsequently used as observations in an orbit determination run considering a full set of forces to determine the orbit over the 10-day time span. All information used is from the TLE data sets. Once the orbit has been determined, it is then numerically propagated to obtain a prediction of the object's position. The TLE-determined orbit is compared to highly accurate satellite laser ranging (SLR) Consolidated Prediction Format (CPF) data to assess the accuracy. We tested the technique by performing 200 independent simulations for Stella, Starlette, Grace A and Grace B and found that it resulted in better orbit predictions 98.5%, 93.4%, 97.5% and 95.5% of the time, respectively, when compared to standard SGP4 propagation. For Stella and Starlette after a 7 day prediction period the average absolute maximum along track bias was reduced by approximately 64% and 74%, respectively. For Grace A and Grace B after a 7 day prediction period the average absolute maximum along track bias was reduced by approximately 68% and 64%, respectively. The TLE-determined orbit contains bias in the along, across and radial tracks with the along track error dominating. If these can be estimated we can obtain an improved orbit prediction. We used our TLE-determined orbit as an initial state and determined an orbit 3 days after the 10 day OD period from only two passes of SLR data from a single station (Mount Stromlo, Australia). We then estimated the bias in the along track direction by fitting a quadratic function to the along track bias data. The error between the TLE-determined orbit and the SLR-determined orbit in the along (minus the quadratic bias), across and radial tracks was then estimated using sinusoidal functions. These estimations were then used to correct the TLE-determined orbit, resulting in drastic improvements in the prediction accuracy of low-<span class="hlt">Earth</span> objects. For a prediction period of 7 days, the absolute maximum along track error for Grace A reduced from 16.6 km (SGP4) to 4.8 km with the TLE data fitting presented in this paper. With bias estimation this error was reduced to 1.7 km. This demonstrates the ability to obtain much more accurate orbit predictions using only two passes (19 normal point SLR ranging observations) from one station. In the operational sense, the presented method can be used in debris conjunction analyses to improve the accuracy and reliability of the conjunction predictions. This method is currently implemented in EOSSS' conjunction analysis software. Objects of interest can then be tracked with EOSSS' tracking facilities and much better orbit predictions can be obtained.</p> <div class="credits"> <p class="dwt_author">Bennett, J.; Sang, J.; Smith, C.; Zhang, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">328</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.B12A..04S"> <span id="translatedtitle">Sorption of Yttrium and the Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> on Non-Living Macroalgal Tissue</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We have investigated sorption of yttrium and the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (YREEs) on tissue of the green macroalga Ulva lactuca, commonly known as sea lettuce. Due to its nearly worldwide distribution in coastal waters, very simple morphology, and prodigious capacity for trace metal uptake from seawater, members of the Ulva genus serve as a basic but representative model of marine organic substrates in this type of study. In order to exclude active biological uptake effects, allowing us to focus on passive chemical mechanisms, we performed our initial experiments with sea lettuce Certified Reference Material consisting of a dehydrated, powdered tissue homogenate. A small quantity of this powder was suspended in NaCl solutions containing all YREEs, except Pm, at pH 3 and T = 25°C. The extent of YREE sorption was determined as a function of pH at constant temperature by titrating the solution with dilute NaOH and measuring the YREE concentrations of 0.2-?m filtered aliquots with an ICP-MS at regular time intervals after each pH adjustment. In NaCl solutions with an ionic strength approaching that of seawater, distribution coefficients, which quantify the proportion of sorbed and dissolved metal concentrations, are a highly linear function of pH in the range 3-8. The slope of the line suggests a sorption mechanism that involves ion exchange with both H+ and Na+ on surface functional groups. The shape of solution YREE patterns indicates that these functional groups are probably carboxylates at low and intermediate pH, but that other groups may contribute at high pH. The identification of carboxylate functional groups appears to be confirmed by preliminary results from EXAFS spectroscopic analyses of individual REE sorbed on the surface of Ulva lactuca tissue under similar conditions, conducted at the ANL Advanced Photon Source. In dilute NaCl solutions the distribution coefficient is largely independent of pH. We believe that prolonged exposure of the tissue to a low ionic strength solution may modify the chemical structure of the cell wall and make it permeable to organic ligands that otherwise sequester the YREEs in the cell interior. Chemical extraction of filtered solutions from the low ionic strength experiment with silica-bonded C18, showing that a substantial fraction of dissolved YREEs is distinctly hydrophobic, seems to support this hypothesis. Additional experiments to clarify these observations, including acid-base titrations of the Ulva lactuca tissue to assess the number of different functional groups and their surface densities, are currently ongoing.</p> <div class="credits"> <p class="dwt_author">Schijf, J.; Straka, A. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">329</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..1611789M"> <span id="translatedtitle">Natural and anthropogenic rare <span class="hlt">earth</span> <span class="hlt">elements</span> in Lago de Paranoá, Brasilia, Brazil</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE) belong to the group of particle reactive <span class="hlt">elements</span> and occur at ultratrace levels in natural waters. They are exclusively trivalent, but Ce and Eu can also be tetravalent and divalent, respectively, depending on the redox-level, the pH and the temperature of the fluid. Due to these redox changes, normalized REE patterns may show Ce and/or Eu anomalies. Recently, these high-tech metals raised significant public attention, as they are of great economic importance and consumption and hence release into the environment increased sharply. The most prominent example of a REE contamination is anthropogenic Gd, which is derived from Gd-based contrast agents used in magnetic resonance imaging. Due to their high stabilities, these compounds are not readily removed by commonly applied waste water treatment technologies and, therefore, are released from treatment plants into surface and ground waters. Hence, this anthropogenic Gd can be used as a tracer for the presence of waste water-derived substances such as pharmaceuticals and personal care products in river, lake, ground and tap waters. Lago de Paranoá is an artificial reservoir lake in the city of Brasilia, Brazil, and is currently considered a potential freshwater resource. The city's two waste water treatment plants are located on its shore and their effluents are discharged into the lake. To investigate the level of contamination, we took water samples at 11 stations in the lake and compared the REE concentrations in unfiltered and filtered (<200 nm) lake water. The unfiltered water samples show light REE enrichment (LaSN/YbSN: 1.37-1.98) and high REE concentrations (Sum REE: 192 - 476 ng/L), while the unfiltered water samples are heavy REE enriched (LaSN/YbSN: 0.15-0.61) at lower concentrations (Sum REE: 50 - 85 ng/L). This is due to the fact that light REE are preferentially bound to particle surfaces, while the heavy REE are preferentially complexed with ligands in solution. In marked contrast to the filtered samples, REE patterns of the unfiltered waters show a positive anomaly of redox-sensitive Ce. This reveals oxidative scavenging of Ce onto particles in the lake water. As lithic particles, such as atmospheric dust, do not show positive Ce anomalies, the particles responsible for Ce oxidation are either inorganic Mn or Fe (oxyhydr-) oxides or organic particulates, which are known to oxidatively scavenge Ce. All samples show pronounced positive Gd anomalies, revealing the presence of waste water-derived anthropogenic Gd in the lake waters. Because the anthropogenic Gd is bound to a very stable water-soluble chemical complex, it does not react with particles. Hence, both the filtered and unfiltered samples show REE patterns with a similar-sized positive Gd anomaly. The presence of anthropogenic Gd indicates that other waste water-derived substances of potentially high (eco-) toxicity may also be present in the lake water. This needs to be further investigated and monitored before using the lake water as a drinking water resource.</p> <div class="credits"> <p class="dwt_author">Merschel, Gila; Baldewein, Linda; Bau, Michael; Dantas, Elton Luiz; Walde, Detlef; Bühn, Bernhard</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">330</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.H53G1032W"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> and uranium-thorium variations in tufa deposits from the Mono Basin, CA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Samples of fossil tufa deposits from several localities in the Mono Basin, eastern California, were analyzed for trace <span class="hlt">element</span> concentrations in order to better understand changes in lake composition in the past. These deposits were formed during the last glacial cycle, mostly during deglaciation (Benson et al., 1990, PPP). Three elevations are represented by the analyses. Samples from near Highway 167 were sampled between 2063 and 2069 m asl. Samples from near Thompson Road were sampled between 2015 and 2021 m. One layered mound was sampled at 1955 m. Concentrations of the lanthanide rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REE), in particular the heavy/light (HREE/LREE) distributions, have been shown to be sensitive to alkalinity in modern saline lakes (e.g., Johannesson et al., 1994, GRL, 21, 773-776), and the same has been suggested for U/Th (Anderson et al., 1982, Science, 216, 514-516). Holocene to near-modern tufa towers exist in shallow water and around the current shoreline (1945 m). Tufa towers above 2000 m include a characteristic morphology termed thinolite, interpreted to represent pseudomorphs after the very cold water mineral ikaite. Most lower elevation towers do not have the thinolite morphology, but some layered tufa mounds at low elevations include several layers of thinolite, such as the one sampled for this project. Analyses were made on millimeter-scale bulk samples from tufa towers. Measurements were made on sample solutions with a Varian 820MS quadrupole ICP-MS. Mono Basin tufa samples have total REE concentrations ranging from 0.029 to 0.77 times average shales. Samples have flat to moderately HREE-enriched shale-normalized patterns with limited overall variability ([La/Lu]SN of 1.8 to 9.6) but with some variability in the slope of the HREE portion of the patterns. Tufa towers sampled from three elevations have (Gd/Lu)SN of 0.40 to 1.5. The REE patterns of most samples have small positive Ce anomalies, but a minority of samples, all from the layered tufa mound, have small negative Ce anomalies. Concentrations of U and Th range from 0.5 to 12 ppm and from 0.2 to 12 ppm, respectively, with substantial variability in U/Th (0.08 to 20). Relative to modern Mono Lake water (Johannesson and Lyons, 1994, Limn. Oc., 39, 1141-1154) the tufa samples have 29 to 144000 times the total REE contents, but the water has HREE/LREE nearly twice as high as the most HREE-enriched fossil tufa. There is a general trend in which samples from higher elevation have lower average total REE, (Gd/Lu)SN and Th and higher average U and U/Th, the latter ranging from 0.52 in the locality at lowest elevation to 10.5 at the highest. In general the results show promise for the application of this approach to paleo-alkalinity, although analyses of modern precipitates as well as laboratory precipitation experiments are needed to fully address the processes.</p> <div class="credits"> <p class="dwt_author">Wilcox, E. S.; Tomascak, P. B.; Hemming, N.; Hemming, S. R.; Rasbury, T.; Stine, S.; Zimmerman, S. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">331</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geokem.com/"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of Igneous Rocks</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">Designed to help graduate students with <span class="hlt">geochemistry</span>, Dr. Bernie Gunn's GeoKem Web site provides referable scientific data and information dealing with volcanic and igneous centers. Originating as a University de Montreal database in 1965, the site contains extensive summaries of research from oceanic ridge basalts to extraterrestrial <span class="hlt">geochemistry</span>. With a vast amount of continually updated data, students can discover the progression, activity, and chemical variability of the Hawaiian Islands, as well as many other island chains. Educators can incorporate the many images and graphs into their lesson plans.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">332</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23085306"> <span id="translatedtitle">Precious metals and rare <span class="hlt">earth</span> <span class="hlt">elements</span> in municipal solid waste--sources and fate in a Swiss incineration plant.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">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 <span class="hlt">elements</span> in the waste input (sources) and their partitioning into recyclable fractions and residues (fate) is unknown. Therefore, a substance flow analysis (SFA) for 31 <span class="hlt">elements</span> including precious metals (Au, Ag), platinum metal group <span class="hlt">elements</span> (Pt, Rh) and rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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 <span class="hlt">element</span> partitioning in the SWI, as well as the <span class="hlt">elemental</span> 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</p> <div class="credits"> <p class="dwt_author">Morf, Leo S; Gloor, Rolf; Haag, Olaf; Haupt, Melanie; Skutan, Stefan; Di Lorenzo, Fabian; Böni, Daniel</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">333</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22622575"> <span id="translatedtitle">Statistical <span class="hlt">geochemistry</span> reveals disruption in secular lithospheric evolution about 2.5?Gyr ago.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The <span class="hlt">Earth</span> has cooled over the past 4.5 billion years (Gyr) as a result of surface heat loss and declining radiogenic heat production. Igneous <span class="hlt">geochemistry</span> has been used to understand how changing heat flux influenced Archaean geodynamics, but records of systematic geochemical evolution are complicated by heterogeneity of the rock record and uncertainties regarding selection and preservation bias. Here we apply statistical sampling techniques to a geochemical database of about 70,000 samples from the continental igneous rock record to produce a comprehensive record of secular geochemical evolution throughout <span class="hlt">Earth</span> history. Consistent with secular mantle cooling, compatible and incompatible <span class="hlt">elements</span> in basalts record gradually decreasing mantle melt fraction through time. Superimposed on this gradual evolution is a pervasive geochemical discontinuity occurring about 2.5?Gyr ago, involving substantial decreases in mantle melt fraction in basalts, and in indicators of deep crustal melting and fractionation, such as Na/K, Eu/Eu* (europium anomaly) and La/Yb ratios in felsic rocks. Along with an increase in preserved crustal thickness across the Archaean/Proterozoic boundary, these data are consistent with a model in which high-degree Archaean mantle melting produced a thick, mafic lower crust and consequent deep crustal delamination and melting--leading to abundant tonalite-trondhjemite-granodiorite magmatism and a thin preserved Archaean crust. The coincidence of the observed changes in <span class="hlt">geochemistry</span> and crustal thickness with stepwise atmospheric oxidation at the end of the Archaean eon provides a significant temporal link between deep <span class="hlt">Earth</span> geochemical processes and the rise of atmospheric oxygen on the <span class="hlt">Earth</span>. PMID:22622575</p> <div class="credits"> <p class="dwt_author">Keller, C Brenhin; Schoene, Blair</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-05-24</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">334</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/doepatents/biblio/873910"> <span id="translatedtitle">Extraction processes and solvents for recovery of cesium, strontium, rare <span class="hlt">earth</span> <span class="hlt">elements</span>, technetium and actinides from liquid radioactive waste</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p class="result-summary">Cesium and strontium are extracted from aqueous acidic radioactive waste containing rare <span class="hlt">earth</span> <span class="hlt">elements</span>, technetium and actinides, by contacting the waste with a composition of a complex organoboron compound and polyethylene glycol in an organofluorine diluent mixture. In a preferred embodiment the complex organoboron compound is chlorinated cobalt dicarbollide, the polyethylene glycol has the formula RC.sub.6 H.sub.4 (OCH.sub.2 CH.sub.2).sub.n OH, and the organofluorine diluent is a mixture of bis-tetrafluoropropyl ether of diethylene glycol with at least one of bis-tetrafluoropropyl ether of ethylene glycol and bis-tetrafluoropropyl formal. The rare <span class="hlt">earths</span>, technetium and the actinides (especially uranium, plutonium and americium), are extracted from the aqueous phase using a phosphine oxide in a hydrocarbon diluent, and reextracted from the resulting organic phase into an aqueous phase by using a suitable strip reagent.</p> <div class="credits"> <p class="dwt_author">Zaitsev, Boris N. (St. Petersburg, RU); Esimantovskiy, Vyacheslav M. (St. Petersburg, RU); Lazarev, Leonard N. (St. Petersburg, RU); Dzekun, Evgeniy G. (Ozersk, RU); Romanovskiy, Valeriy N. (St. Petersburg, RU); Todd, Terry A. (Aberdeen, ID); Brewer, Ken N. (Arco, ID); Herbst, Ronald S. (Idaho Falls, ID); Law, Jack D. (Pocatello, ID)</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">335</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/15701392"> <span id="translatedtitle">Distribution of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in an alluvial aquifer affected by acid mine drainage: the Guadiamar aquifer (SW Spain).</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">This work analyses the spatial distribution, the origin, and the shale-normalised fractionation patterns of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (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 <span class="hlt">elements</span>, 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 <span class="hlt">earth</span> <span class="hlt">elements</span> (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</p> <div class="credits"> <p class="dwt_author">Olías, M; Cerón, J C; Fernández, I; De la Rosa, J</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">336</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/3902778"> <span id="translatedtitle">The <span class="hlt">geochemistry</span> of strontium</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">geochemistry</span> of strontium has been investigated, using an emission spectrographic technique checked by isotope dilution analyses described elsewhere ( et al., in press). Hence the determinations are claimed to have good accuracy as well as precision. Approximately 700 analyses have been made on silicate rocks and over 300 on carbonate materials (a detailed analysis of the latter appearing in</p> <div class="credits"> <p class="dwt_author">Karl K. Turekian; J. Laurence Kulp</p> <p class="dwt_publisher"></p> <p class="publishDate">1956-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">337</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013IJEaS.tmp...16S"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of Proterozoic granitoids exposed between Dirang and Tawang, western Arunachal Himalaya, north-eastern India: petrogenetic and tectonic significance</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Major and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of Proterozoic granitoids from the Dirang and Galensiniak Formations, of Lesser and Higher Himalayas, respectively, emplaced in and around Dirang and Tawang regions of the western Arunachal Himalaya, is discussed. In general, these granitoids are massive as well as foliated in nature and are characterized by granitic mineralogical compositions. Porphyritic and hypidiomorphic textures are common in massive type, whereas others show porphyroblastic and foliated textures. Augen structure is also observed in a number of samples. Geochemical and normative compositions together with petrographic features classify them as peraluminous granitoids. Major and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> of most of these granitoids shows granitic nature, while few samples also show monzonitic characteristics. Observed geochemical characters, such as their peraluminous and alkali-calcic/calcic-alkalic nature, crudely defined geochemical patterns, different multi-<span class="hlt">element</span> and rare-<span class="hlt">earth</span> <span class="hlt">element</span> patterns, together with low Mg# (Mg number) of these granitoids suggest their derivation from lower crustal material rather than a mantle source. Multi-<span class="hlt">element</span> and rare-<span class="hlt">earth</span> <span class="hlt">element</span> patterns corroborate their genesis from different crustal melts. It is difficult to explain variations observed in granitoid rocks by partial melting alone; definitely different other processes like migration of melts, magma mixing, assimilation and fractional crystallization also played important role in the genesis of these granitoids. These melts were likely generated at low temperature (730-760 °C) and low pressure (2-5 GPa). The chemical compositions suggest that most of these Paleoproterozoic granitoids are emplaced within the syn-collisional tectonic setting, while few granitoid samples also indicate their volcanic-arc nature. Probably, later group of granitoids are slightly younger to the syn-collisional type.</p> <div class="credits"> <p class="dwt_author">Srivastava, Rajesh K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">338</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006Geomo..80..147J"> <span id="translatedtitle"><span class="hlt">Geochemistry</span> of Daihai Lake sediments, Inner Mongolia, north China: Implications for provenance, sedimentary sorting, and catchment weathering</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">To advance the understanding of sediment distribution, catchment weathering, hydraulic sorting, and sediment provenance in a tectonically stable basin, the <span class="hlt">geochemistry</span> of surface sediment samples from Daihai Lake in north China is presented. Mud bulk sediments were analyzed for 10 major and 30 trace <span class="hlt">elements</span>, organic carbon, and nitrogen and for 87Sr/ 86Sr ratios in silicate fraction (acid insoluble, AI) and carbonates (acid soluble, AS). Enrichment in Fe 2O 3, CaO, MnO, MgO, K 2O, and P 2O 5 and their positive correlation with Al 2O 3, Rb/Sr ratios, and bivariate discrimination diagrams of K vs. Rb and Th/U vs. Th suggest low chemical weathering intensity under semiarid conditions in the Daihai catchment. Accumulation of clays in deeper water sites by sedimentary sorting results in an evident distribution of sediment composition with the lake water depth. Although similar chondrite-normalized REE (rare <span class="hlt">earth</span> <span class="hlt">element</span>) patterns of lake sediment samples (with LREE (light rare <span class="hlt">earth</span> <span class="hlt">element</span>) enrichment, negative Eu anomalies, and an almost flat HREE (heavy rare <span class="hlt">earth</span> <span class="hlt">element</span>) pattern) may suggest similar sedimentary source rocks, original sediment provenance can be recognized on the basis of their distinctive 87Sr/ 86Sr (AI) ratios and immobile (Th, Zr, Ti, and Nb) trace <span class="hlt">element</span> signature, separating from weathering and sedimentary processes as well as from grain size effect.</p> <div class="credits"> <p class="dwt_author">Jin, Zhangdong; Li, Fuchun; Cao, Junji; Wang, Sumin; Yu, Jimin</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">339</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70024831"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> variations resulting from inversion of pigeonite and subsolidus reequilibration in lunar ferroan anorthosites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">We present results of a secondary ion mass spectrometry study of the rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in the minerals of two samples of lunar ferroan anorthosite, and the results are applicable to studies of REEs in all igneous rocks, no matter what their planet of origin. Our pyroxene analyses are used to determine solid-solid REE distribution coefficients (D = CREE in low-Ca pyroxene/CREE in augite) in orthopyroxene-augite pairs derived by inversion of pigeonite. Our data and predictions from crystal-chemical considerations indicate that as primary pigeonite inverts to orthopyroxene plus augite and subsolidus reequilibration proceeds, the solid-solid Ds for orthopyroxene-augite pairs progressively decrease for all REEs; the decrease is greatest for the LREEs. The REE pattern of solid-solid Ds for inversion-derived pyroxene pairs is close to a straight line for Sm-Lu and turns upward for REEs lighter than Sm; the shape of this pattern is predicted by the shapes of the REE patterns for the individual minerals. Equilibrium liquids calculated for one sample from the compositions of primary phases, using measured or experimentally determined solid-liquid Ds, have chondrite-normalized REE patterns that are very slightly enriched in LREEs. The plagioclase equilibrium liquid is overall less rich in REEs than pyroxene equilibrium liquids, and the discrepancy probably arises because the calculated plagioclase equilibrium liquid represents a liquid earlier in the fractionation sequence than the pyroxene equilibrium liquids. "Equilibrium" liquids calculated from the compositions of inversion-derived pyroxenes or orthopyroxene derived by reaction of olivine are LREE depleted (in some cases substantially) in comparison with equilibrium liquids calculated from the compositions of primary phases. These discrepancies arise because the inversion-derived and reaction-derived pyroxenes did not crystallize directly from liquid, and the use of solid-liquid Ds is inappropriate. The LREE depletion of the calculated liquids is a relic of formation of these phases from primary LREE-depleted minerals. Thus, if one attempts to calculate the compositions of equilibrium liquids from pyroxene compositions, it is important to establish that the pyroxenes are primary. In addition, our data suggest that experimental studies have underestimated solid-liquid Ds for REEs in pigeonite and that REE contents of liquids calculated using these Ds are overestimates. Our results have implications for Sm-Nd age studies. Our work shows that if pigeonite inversion and/or subsolidus reequilibration between augite and orthopyroxene occured significantly after crystallization, and if pyroxene separates isolated for Sm-Nd studies do not have the bulk composition of the primary pyroxenes, then the Sm-Nd isochron age and ??Nd will be in error. Copyright ?? 2002 Elsevier Science Ltd.</p> <div class="credits"> <p class="dwt_author">James, O.B.; Floss, C.; McGee, J.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">340</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFM.B31F..08S"> <span id="translatedtitle">Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> - Humic Acid Interaction: Experimental Evidence for Kinetic and Equilibrium Fractionation in Aqueous Systems.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">Earth</span> <span class="hlt">Element</span> (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.</p> <div class="credits"> <p class="dwt_author">Sonke, J. E.; Salters, V. J.; Benedetti, M. F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_16");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">341</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41857215"> <span id="translatedtitle">Effects of Rare <span class="hlt">Earth</span> <span class="hlt">Elements</span> on the Growth of Arnebia euchroma Cells and the Biosynthesis of Shikonin</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Nd3+, La3+ and Ce3+ at proper concentrations had positive effects on the cell growth of Arnebia euchroma and production of shikonin derivatives. A mixture of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (MRE, La2O3:CeO2:Pr6O11: Sm2O3 = 255:175:3:1, mol\\/mol) behaved the most remarkable effects. Two-stage culture was used for the cell proliferation and the\\u000a biosynthesis of shikonin derivatives. After 20 days culture, 0.05 mM MRE gave the highest cell biomass</p> <div class="credits"> <p class="dwt_author">Feng Ge; Xiaodong Wang; Bing Zhao; Yuchun Wang</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">342</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/38431/5/p13-19-origin08.pdf"> <span id="translatedtitle">Origin and Evolution of Life: Endless Ordering of the <span class="hlt">Earth</span>'s Light <span class="hlt">Elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The evolution of a living organism, as well as pre-biotic molecular evolution, seems to be incon- sistent with the second law of thermodynamics. When a bacterium is compared with some other higher organism, it is clear that all evolution tends to order more and larger molecules into more complex systems. The trick is the radiation of heat from the <span class="hlt">Earth</span>.</p> <div class="credits"> <p class="dwt_author">Hiromoto Nakazawa</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">343</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=233107"> <span id="translatedtitle">Mixing rare <span class="hlt">earth</span> <span class="hlt">elements</span> with manures to control phosphorus loss in runoff and track manure fate</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">Concern over the enrichment of agricultural runoff with phosphorus (P) from land applied livestock manures has prompted the development of manure amendments that minimize P solubility. We evaluated the effect of mixing two rare <span class="hlt">earth</span> chlorides, lanthanum chloride and ytterbium chloride, with poultr...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">344</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014Litho.190..363L"> <span id="translatedtitle">Petrogenesis of the Late Triassic volcanic rocks in the Southern Yidun arc, SW China: Constraints from the geochronology, <span class="hlt">geochemistry</span>, and Sr-Nd-Pb-Hf isotopes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Studies on zircon ages, petrology, major and trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>, and Sr-Nd-Hf-Pb isotopic <span class="hlt">geochemistry</span> of intermediate volcanic rocks from the Southern Yidun arc, Sanjiang-Tethyan Orogenic Belt, SW China have been undertaken in this paper. They are used to discuss the petrogenesis of these rocks and to constrain the tectonic setting and evolution of the Yidun arc. These intermediate volcanic rocks were erupted at ca. 220 Ma (U-Pb zircon ages). Trachyandesite is the dominant lithology among these volcanic rocks, and is mainly composed of hornblende and plagioclase, with minor clinopyroxene and biotite. A hornblende geobarometer suggests that the stagnation of magma in the lower crust, where plagioclase crystallization was suppressed while hornblende crystallized, giving rise to high Sr/Y ratios that are one of the distinguishing features of adakites, after the primary magma originated from the lithospheric mantle wedge. Steeply right-inclined Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> (REE) pattern combined with high La/Yb ratios suggests adakitic affinity of these volcanic rocks, implying that slab-melt from the subducting oceanic crust is a necessary component in the primary magma. Besides, trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> and isotopic <span class="hlt">geochemistry</span> also indicate that partial melting of pelagic sediments in the subduction zone and noticeable contamination with the lower crust were involved in the evolution of parental magma of these volcanic rocks. Based on previous work on the Northern Yidun arc and this study, we propose that the subduction was initiated in the Northern Yidun arc and extended to the southern part and that the Northern Yidun arc is an island arc while the Southern Yidun arc represents a continental arc, probably caused by the existence of the Zhongza Massif, that was invoked to be derived from Yangtze Block, as a possible basement of the Southern Yidun arc.</p> <div class="credits"> <p class="dwt_author">Leng, Cheng-Biao; Huang, Qiu-Yue; Zhang, Xing-Chun; Wang, Shou-Xu; Zhong, Hong; Hu, Rui-Zhong; Bi, Xian-Wu; Zhu, Jing-Jing; Wang, Xin-Song</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">345</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=Hydrology&pg=4&id=EJ032449"> <span id="translatedtitle"><span class="hlt">Earth</span> Science in 1970</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">Reviews advancements in <span class="hlt">earth</span> science during 1970 in each of these areas: economic geology (fuels), economic geology (metals), economic geology (nonmetals), environmental geology, <span class="hlt">geochemistry</span>, manpower, hydrology, mapping, marine geology, mineralogy, paleontology, plate tectonics, politics and geology, remote sensing, and seismology. (PR)</p> <div class="credits"> <p class="dwt_author">Geotimes, 1971</p> <p class="dwt_publisher"></p> <p class="publishDate">1971-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">346</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24793516"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> in intertidal sediments of Bohai Bay, China: concentration, fractionation and the influence of sediment texture.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Surface sediments from intertidal Bohai Bay were assessed using a four-step sequential extraction procedure to determine their concentrations of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) and the chemical forms in which those <span class="hlt">elements</span> were present. The normalized ratios La/Gd and La/Yb showed that LREE contents were not significantly higher than the middle REEs or HREE contents. A negative Ce anomaly and positive Eu were observed in sand and silty sand sediments, whereas no significant Ce or Eu anomaly was found in clayey silt sediments. Residual fraction of REEs accounted for the majority of their total concentrations. Middle REEs were more easily leached than other REEs, especially in clayey silt sediment. REEs contents in the surface sediment from the intertidal Bohai Sea were consistent with data from the upper continental crust and China shallow sea sediments, indicating that they were generally unaffected by heavily anthropogenic effects from adjacent areas. PMID:24793516</p> <div class="credits"> <p class="dwt_author">Zhang, Yong; Gao, Xuelu; Arthur Chen, Chen-Tung</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">347</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003TrGeo...5..225G"> <span id="translatedtitle">Trace <span class="hlt">Elements</span> in River Waters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Trace <span class="hlt">elements</span> are characterized by concentrations lower than 1 mg L-1 in natural waters. This means that trace <span class="hlt">elements</span> are not considered when "total dissolved solids" are calculated in rivers, lakes, or groundwaters, because their combined mass is not significant compared to the sum of Na+, K+, Ca2+, Mg2+, H4SiO4, HCO3-, CO32-, SO42-, Cl-, and NO3-. Therefore, most of the <span class="hlt">elements</span>, except about ten of them, occur at trace levels in natural waters. Being trace <span class="hlt">elements</span> in natural waters does not necessarily qualify them as trace <span class="hlt">elements</span> in rocks. For example, aluminum, iron, and titanium are major <span class="hlt">elements</span> in rocks, but they occur as trace <span class="hlt">elements</span> in waters, due to their low mobility at the <span class="hlt">Earth</span>'s surface. Conversely, trace <span class="hlt">elements</span> in rocks such as chlorine and carbon are major <span class="hlt">elements</span> in waters.The <span class="hlt">geochemistry</span> of trace <span class="hlt">elements</span> in river waters, like that of groundwater and seawater, is receiving increasing attention. This growing interest is clearly triggered by the technical advances made in the determination of concentrations at lower levels in water. In particular, the development of inductively coupled plasma mass spectrometry (ICP-MS) has considerably improved our knowledge of trace-<span class="hlt">element</span> levels in waters since the early 1990s. ICP-MS provides the capability of determining trace <span class="hlt">elements</span> having isotopes of interest for geochemical dating or tracing, even where their dissolved concentrations are extremely low.The determination of trace <span class="hlt">elements</span> in natural waters is motivated by a number of issues. Although rare, trace <span class="hlt">elements</span> in natural systems can play a major role in hydrosystems. This is particularly evident for toxic <span class="hlt">elements</span> such as aluminum, whose concentrations are related to the abundance of fish in rivers. Many trace <span class="hlt">elements</span> have been exploited from natural accumulation sites and used over thousands of years by human activities. Trace <span class="hlt">elements</span> are therefore highly sensitive indexes of human impact from local to global scale. Pollution impact studies require knowledge of the natural background concentrations and knowledge of pollutant behavior. For example, it is generally accepted that rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in waters behave as good analogues for the actinides, whose natural levels are quite low and rarely measured. Water quality investigations have clearly been a stimulus for measurement of toxic heavy metals in order to understand their behavior in natural systems.From a more fundamental point of view, it is crucial to understand the behavior of trace <span class="hlt">elements</span> in geological processes, in particular during chemical weathering and transport by waters. Trace <span class="hlt">elements</span> are much more fractionated by weathering and transport processes than major <span class="hlt">elements</span>, and these fractionations give clues for understanding the nature and intensity of the weathering+transport processes. This has not only applications for weathering studies or for the past mobilization and transport of <span class="hlt">elements</span> to the ocean (potentially recorded in the sediments), but also for the possibility of better utilization of trace <span class="hlt">elements</span> in the aqueous environment as an exploration tool.In this chapter, we have tried to review the recent literature on trace <span class="hlt">elements</span> in rivers, in particular by incorporating the results derived from recent ICP-MS measurements. We have favored a "field approach" by focusing on studies of natural hydrosystems. The basic questions which we want to address are the following: What are the trace <span class="hlt">element</span> levels in river waters? What controls their abundance in rivers and fractionation in the weathering+transport system? Are trace <span class="hlt">elements</span>, like major <span class="hlt">elements</span> in rivers, essentially controlled by source-rock abundances? What do we know about the chemical speciation of trace <span class="hlt">elements</span> in water? To what extent do colloids and interaction with solids regulate processes of trace <span class="hlt">elements</span> in river waters? Can we relate the <span class="hlt">geochemistry</span> of trace <span class="hlt">elements</span> in aquatic systems to the periodic table? And finally, are we able to satisfactorily model and predict the behavior of most of the trace <span class="hlt">elements</span> </p> <div class="credits"> <p class="dwt_author">Gaillardet, J.; Viers, J.; Dupré, B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">348</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001AGUFM.V51B1006K"> <span id="translatedtitle">Rare <span class="hlt">Earth</span> <span class="hlt">Element</span> Mapping of Garnet by Laser Ablation ICP-MS</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The introduction of the electron microprobe brought tremendous advancement to our understanding of mineral forming reactions, thermobarometry and the patterns and controls of major <span class="hlt">element</span> zoning. Today, the application of laser ablation ICP-MS (LA-ICP-MS) is providing the same advancements, but at the trace <span class="hlt">element</span> scale. While considerable attention has been paid to the behavior of trace <span class="hlt">elements</span> in a crystal-melt system, the number of studies addressing trace <span class="hlt">elements</span> in metamorphic minerals is few. We have developed methods using LA-ICP-MS to rapidly construct quantitative trace <span class="hlt">element</span> maps of geologic (minerals, corals, coal, etc.) and non-geologic (tree rings, sheep horns, fish scales, metals, etc.) materials. Experimental determination of trace <span class="hlt">element</span> partitioning and the parameters that control it are determined almost exclusively on experimental melt products and natural glasses. With this study we demonstrate that insight into the behavior of the trace <span class="hlt">elements</span> during metamorphic mineral growth is now readily obtainable. Garnets from the Nason terrane, North Cascades, WA, USA have been analyzed in order to study trace <span class="hlt">element</span> heterogeneity. In the Nason terrane, almandine-rich garnets in amphibolite facies rocks all possess distinct enhanced HREE compatibility in the cores with varying degrees of complex zoning towards the rim. A distinct trace-<span class="hlt">element</span>-enriched annulus is present in nearly all garnets studied. Annuli enriched in the HREEs and Y are common, but annuli enriched only in the LREEs are also present. We suggest the annuli are the result of the breakdown of REE-rich minerals such as monazite, apatite and/or xenotime. The HREE zoning patterns from rim to core can be used to model the changing mechanism for growth zoning. While it is clear that various mechanisms operate during the entire growth history, it appears that intercrystalline diffusion is the dominant mechanism producing HREE zoning in the early stages of garnet growth.</p> <div class="credits"> <p class="dwt_author">Koenig, A. E.; Koenig, A. E.; Magloughlin, J. F.; Ridley, W. I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">349</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/51604447"> <span id="translatedtitle">Trace <span class="hlt">element</span> and Sr and Nd isotope <span class="hlt">geochemistry</span> of peridotite xenoliths from the Eifel (West Germany) and their bearing on the evolution of the subcontinental lithosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Peridotite xenoliths from the Eifel can be divided into incompatible <span class="hlt">element</span>-depleted and -enriched members. The depleted group is restricted to dry lherzolites whereas the enriched group encompasses dry harzburgites, dry websterite and amphibole and\\/or phlogopite-bearing peridotites. Isotopically the depleted group is very diverse with 143Nd\\/144Nd ranging from ~ 0.51302 to 0.51355 and 87Sr\\/86Sr from ~ 0.7041 to 0.7019, thus occupying</p> <div class="credits"> <p class="dwt_author">H.-G. Stosch; G. W. Lugmair</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">350</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013Litho.170...35G"> <span id="translatedtitle">U-Pb dates and trace-<span class="hlt">element</span> <span class="hlt">geochemistry</span> of zircon from migmatite, Western Gneiss Region, Norway: Significance for history of partial melting in continental subduction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Western Gneiss Region (WGR), Norway, is dominated by migmatitic gneiss that contains inclusions of eclogite, some of which contain evidence for ultrahigh-pressure metamorphism. To evaluate geochemical and age relationships between host migmatite and eclogite, we obtained LA-ICP-MS U-Pb dates and trace-<span class="hlt">element</span> analyses for zircon from a variety of textural types of leucosome, from layer-parallel to crosscutting. Zircon textures (euhedral, oscillatory- and sector-zone grains) indicate a likely magmatic origin of the leucosomes. Caledonian U-Pb zircon dates from zircon rim and near-rim regions are as old as 410-406 Ma, coeval with previously determined ages of high- and ultrahigh-pressure metamorphism of WGR eclogite. Trace-<span class="hlt">element</span> analyses obtained simultaneously with U-Pb dates indicate crystallization of zircon under garnet-present conditions in the majority of leucosomes. Other zircons, including those from crosscutting pegmatite, yield younger ages (as young as 385 Ma), coinciding with dates determined for amphibolite-facies retrogression of eclogite; trace-<span class="hlt">element</span> analyses suggest that these zircons grew under plagioclase-present (garnet-absent) conditions. Combined age and trace-<span class="hlt">element</span> data for leucosome zircons record the transition from high-pressure (garnet-present, plagioclase-absent) crystallization to lower-pressure (plagioclase-present) crystallization. If the euhedral zircons that yield ages coeval with peak or near-peak UHP metamorphism represent crystallization from anatectic leucosomes, these results, combined with field and petrographic observations of eclogite-migmatite relationships, are consistent with the presence of partially molten crust in at least part of the WGR during continental subduction. The decreased viscosity and increased buoyancy and strain weakening associated with partial melting may have assisted the rapid ascent of rocks from mantle to crustal depths.</p> <div class="credits"> <p class="dwt_author">Gordon, Stacia M.; Whitney, Donna L.; Teyssier, Christian; Fossen, Haakon</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">351</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48160013"> <span id="translatedtitle">Geology, <span class="hlt">geochemistry</span> and mineralogy of the lignite-hosted Ambassador palaeochannel uranium and multi-<span class="hlt">element</span> deposit, Gunbarrel Basin, Western Australia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Ambassador U and multi-<span class="hlt">element</span> deposit occurs on the SW margin of the Gunbarrel Basin, Western Australia. Low-grade, flat-lying\\u000a U mineralization averaging about 2 m thick at 0.03% U occurs in lignites at the redox front at the base of the weathering\\u000a profile within a laterally extensive palaeochannel network. Uranium is principally associated with organic matter within the\\u000a lignitic matrix, although</p> <div class="credits"> <p class="dwt_author">Grant B. Douglas; Charles R. M. Butt; David J. Gray</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">352</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19810040416&hterms=Mica&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMica"> <span id="translatedtitle">Halogen and phosphorus storage in the <span class="hlt">earth</span>. [<span class="hlt">elemental</span> spatial distribution from geochemical, geophysical, and cosmochemical factors</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Chemical analyses of surface reservoirs, coupled with compositions for interior zones inferred from geophysical and geochemical data have been used to obtain a range of estimates of the bulk composition of the <span class="hlt">earth</span>. It is suggested that (1) apatite with 3 wt% Fe, up to 1 wt% Cl, and 0.003 wt% Br is the principal mineral reservoir for halogens, and mica is a subsidiary reservoir; (2) apatite with 18 wt% P is the principal store of P in the upper mantle and perhaps lower mantle, but accounts for only one-twentieth of P in the <span class="hlt">earth</span>; and (3) the remaining P is in a reservoir inaccessible to magmatism, and may amount to a maximum of 0.7 wt% in the core.</p> <div class="credits"> <p class="dwt_author">Smith, J. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">1981-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">353</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19495997"> <span id="translatedtitle">Species and distribution of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Baotou section of the Yellow River in China.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">This paper analyses the contents and species distributions of rare <span class="hlt">earth</span> <span class="hlt">elements</span> (REEs) in the water-suspended particulate-sediment system of the Baotou section of the Yellow River, China, with known anthropogenic REE input from industrial discharges. The major forms of REEs were suspended and dissolved in the mainstream and the tributaries of the Baotou section, respectively. The concentrations of the dissolved and suspended REEs had the same trends in the overlying water along the mainstream, which increased from the Seqi section (site A) to the mouth of the Sidaosha River (site D), reaching a maximum value at site D, and tending to decrease thereafter. The contents of REEs in sediment cores showed enrichment with light rare <span class="hlt">earth</span> <span class="hlt">elements</span> (LREEs). The bound to carbonates and to Fe-Mn oxides are the major forms of REE in the secondary phase and the REE exhibited LREE enrichment pattern and moderate Eu depletion in suspended particulates and surface sediments. The contents and species distributions of REEs in the water-suspended particulate-sediment system of the Baotou section suggest that the anthropogenic source of REEs from Baotou city have enhanced REE accumulation to the Baotou section. This information is important for predicting possible pollution resulting from anthropogenic REE input into rivers. PMID:19495997</p> <div class="credits"> <p class="dwt_author">He, Jiang; Lü, Chang-Wei; Xue, Hong-Xi; Liang, Ying; Bai, Saruli; Sun, Ying; Shen, Li-Li; Mi, Na; Fan, Qing-Yun</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">354</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/pp1596"> <span id="translatedtitle">Geochemical studies of rare <span class="hlt">earth</span> <span class="hlt">elements</span> in the Portuguese pyrite belt, and geologic and geochemical controls on gold distribution</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">This report describes geochemical and geological studies which were conducted by the U.S. Geological Survey (USGS) and the Servicos Geologicos de Portugal (SPG) in the Portuguese pyrite belt (PPB) in southern Portugal. The studies included rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE) distributions and geological and geochemical controls on the distribution of gold. Rare <span class="hlt">earth</span> <span class="hlt">element</span> distributions were determined in representative samples of the volcanic rocks from five west-trending sub-belts of the PPB in order to test the usefulness of REE as a tool for the correlation of volcanic events, and to determine their mobility and application as hydrothermal tracers. REE distributions in felsic volcanic rocks show increases in the relative abundances of heavy REE and a decrease in La/Yb ratios from north to south in the Portuguese pyrite belt. Anomalous amounts of gold are distributed in and near massive and disseminated sulfide deposits in the PPB. Gold is closely associated with copper in the middle and lower parts of the deposits. Weakly anomalous concentrations of gold were noted in exhalative sedimentary rocks that are stratigraphically above massive sulfide deposits in a distal manganiferous facies, whereas anomalously low concentrations were detected in the barite-rich, proximal-facies exhalites. Altered and pyritic felsic volcanic rocks locally contain highly anomalous concentrations of gold, suggesting that disseminated sulfide deposits and the non-ore parts of massive sulfide deposits should be evaluated for their gold potential.</p> <div class="credits"> <p class="dwt_author">Grimes, David J.; Earhart, Robert L.; de Carvalho, Delfim; Oliveira, Vitor; Oliveira, Jose T.; Castro, Paulo</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">355</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40479672"> <span id="translatedtitle">Microstructural characteristics of laser clad coatings with rare <span class="hlt">earth</span> metal <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The microstructural characteristics of laser clad nickel-based alloy coatings with rare <span class="hlt">earth</span> (RE) oxide CeO2 or La2O3 were investigated. Nickel-based alloy powder with different contents of CeO2 or La2O3 was laser clad onto a steel substrate. The clad coatings were examined and tested for microstructural features, chemical compositions and phase structure of the clad coatings. A scanning electron microscope (SEM)</p> <div class="credits"> <p class="dwt_author">K. L. Wang; Q. B. Zhang; M. L. Sun; X. G. Wei</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">356</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40366853"> <span id="translatedtitle">Microstructure and corrosion resistance of laser clad coatings with rare <span class="hlt">earth</span> <span class="hlt">elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The effects of rare <span class="hlt">earth</span> oxides CeO2 and La2O3 on the microstructure and corrosion resistance of laser clad nickel-based alloy coatings were investigated. The nickel-based alloy powder with CeO2 or La2O3 was laser clad on to a steel substrate. The coatings were examined for microstructural features, compositions, phase structure and corrosion resistance. The results were compared with those for coatings</p> <div class="credits"> <p class="dwt_author">K. L. Wang; Q. B. Zhang; M. L. Sun; X. G. Wei; Y. M. Zhu</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">357</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40307930"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">elements</span> modification of laser-clad nickel-based alloy coatings</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The effects of rare <span class="hlt">earth</span> oxide CeO2 and La2O3 on the microstructure and wear resistance of laser-clad nickel-based alloy coatings were investigated. The nickel-based alloy powders with different contents of CeO2 or La2O3 were laser-clad on to a steel substrate. The coatings were examined and tested for microstructural features, compositions, phase structure, and wear resistance. The results were compared with</p> <div class="credits"> <p class="dwt_author">K. L Wang; Q. B Zhang; M. L Sun; X. G Wei; Y. M Zhu</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">358</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/43797199"> <span id="translatedtitle">Spectral-finite <span class="hlt">element</span> approach to three-dimensional electromagnetic induction in a spherical <span class="hlt">earth</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We present a spectral-finite <span class="hlt">element</span> approach to the forward problem of 3-Dglobal-scale electromagnetic induction in a heterogeneous conducting sphere excited by an external source current. It represents an alternative to a variety of numerical methods for 3-D global-scale electromagnetic induction modelling developed recently (the perturbation expansion approach and the finite <span class="hlt">element</span> and finite difference schemes). Two possible formulations of electromagnetic</p> <div class="credits"> <p class="dwt_author">Zdenek Martinec</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">359</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/741398.pdf"> <span id="translatedtitle">(Data in metric tons of yttrium oxide (Y O ) content, unless otherwise noted)2 3 Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined by one company as a constituent of the</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">.20.0000 Free Free. Rare-<span class="hlt">earth</span> metals, scandium and yttrium, whether or not intermixed or interalloyed 2805 Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined by one company as a constituent of the mineral bastnasite, but was not recovered as a separate <span class="hlt">element</span> during processing. Bastnasite, a rare-<span class="hlt">earth</span></p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">360</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/yttrimcs96.pdf"> <span id="translatedtitle">(Data in metric tons of yttrium oxide (Y2O3) content, unless noted) Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined by one company as a constituent of the</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">ores and concentrates (monazite) 2612.20.0000 Free Free. Rare-<span class="hlt">earth</span> metals, scandium and yttrium Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined by one company as a constituent of the mineral bastnasite, but was not recovered as a separate <span class="hlt">element</span> during processing. Bastnasite, a rare-<span class="hlt">earth</span></p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_17");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">361</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/741301.pdf"> <span id="translatedtitle">(Data in metric tons of yttrium oxide (Y2O3) content, unless otherwise noted) Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span> yttrium was mined as a constituent of the mineral bastnasite,</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">and concentrates (monazite) 2612.20.0000 Free. Rare-<span class="hlt">earth</span> metals, scandium and yttrium, whether or not intermixed Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span> yttrium was mined as a constituent of the mineral bastnasite, but was not recovered as a separate <span class="hlt">element</span> during processing. Bastnasite, a rare-<span class="hlt">earth</span> fluocarbonate mineral, was mined</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">362</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/741300.pdf"> <span id="translatedtitle">(Data in metric tons of yttrium oxide (Y2O3) content, unless otherwise noted) Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined as a constituent of the mineral</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">.20.0000 Free. Rare-<span class="hlt">earth</span> metals, scandium and yttrium, whether or not intermixed or interalloyed 2805.30.0000 5 Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined as a constituent of the mineral bastnasite, but was not recovered as a separate <span class="hlt">element</span> during processing. Bastnasite, a rare-<span class="hlt">earth</span> fluocarbonate mineral, was mined</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">363</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/741397.pdf"> <span id="translatedtitle">(Data in metric tons of yttrium oxide (Y O ) content, unless otherwise noted)2 3 Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined by one company as a constituent of the</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">/31/96 Thorium ores and concentrates (monazite) 2612.20.0000 Free Free. Rare-<span class="hlt">earth</span> metals, scandium and yttrium Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined by one company as a constituent of the mineral bastnasite, but was not recovered as a separate <span class="hlt">element</span> during processing. Bastnasite, a rare-<span class="hlt">earth</span></p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">364</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/741399.pdf"> <span id="translatedtitle">(Data in metric tons of yttrium oxide (Y O ) content, unless otherwise noted)2 3 Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined as a constituent of the mineral bastnasite,</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">/31/98 Thorium ores and concentrates (monazite) 2612.20.0000 Free Free. Rare-<span class="hlt">earth</span> metals, scandium and yttrium Domestic Production and Use: The rare-<span class="hlt">earth</span> <span class="hlt">element</span>, yttrium, was mined as a constituent of the mineral bastnasite, but was not recovered as a separate <span class="hlt">element</span> during processing. Bastnasite, a rare-<span class="hlt">earth</span></p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">365</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70014010"> <span id="translatedtitle">The group separation of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> and yttrium from geologic materials by cation-exchange chromatography</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Demand is increasing for the determination of the rare-<span class="hlt">earth</span> <span class="hlt">elements</span> (REE) and yttrium in geologic materials. Due to their low natural abundance in many materials and the interferences that occur in many methods of determination, a separation procedure utilizing gradient strong-acid cation-exchange chromatography is often used to preconcentrate and isolate these <span class="hlt">elements</span> from the host-rock matrix. Two separate gradient strong-acid cation-exchange procedures were characterized and the major <span class="hlt">elements</span> as well as those <span class="hlt">elements</span> thought to provide the greatest interference for the determination of the REE in geologic materials were tested for separation from the REE. Simultaneous inductively coupled argon plasma-atomic emission spectroscopy (ICAP-AES) measurements were used to construct the chromatograms for the elution studies, allowing the elution patterns of all the <span class="hlt">elements</span> of interest to be determined in a single fraction of eluent. As a rock matrix, U.S. Geological Survey standard reference BCR-1 basalt was digested using both an acid decomposition procedure and a lithium metaborate fusion. Hydrochloric and nitric acids were tested as eluents and chromatograms were plotted using the ICAP-AES data; and we observed substantial differences in the elution patterns of the REE and as well as in the solution patterns of Ba, Ca, Fe and Sr. The nitric acid elution required substantially less eluent to elute the REE and Y as a group when compared to the hydrochloric acid elution, and provided a clearer separation of the REE from interfering and matrix <span class="hlt">elements</span>. ?? 1984.</p> <div class="credits"> <p class="dwt_author">Crock, J.G.; Lichte, F.E.; Wildeman, T.R.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">366</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.V33C2228B"> <span id="translatedtitle">Trace <span class="hlt">Element</span> <span class="hlt">Geochemistry</span> including the HFSE in Magnetites of Calc-Alkaline Plutons: the Tanzawa Complex of the Izu-Bonin-Mariana Arc and the Ladakh Batholith Complex, NW Himalaya</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In this study we attempt to contribute to the understanding of a prominent feature, namely the Nb-Ta depletion, in arc magmatic trace <span class="hlt">element</span> <span class="hlt">geochemistry</span>. Traditionally, this depletion is explained by residual mantle-wedge phases with Nb and Ta affinities, such as titaniferous ilmenite, rutile or titanite, or by an amphibole. Here we propose a mechanism long advocated to explain the calc-alkaline trend (Bowen vs. Fenner) in MgO-FeO (total Fe)-(Na2O + K2O) ternary diagram by early crystallization and separation of magnetite in subduction zone magmas associated with high oxygen fugacity environments. In support of our hypothesis we provide high-precision multiple trace <span class="hlt">element</span> data, including the high field strength <span class="hlt">elements</span> (HFSE), in separated magnetites and mafic mineral phases from mafic magmatic enclaves associated with tonalite suites of two different magmatic arcs - the Tanzawa Complex of the Izu-Tanzawa Collision Zone in Japan, and from the Ladakh Batholith Complex of NW Himalayas. The Tanzawa Complex is composed of diverse rock suites with SiO2 varying from 43 - 75 percent, ranging from hornblende gabbro through tonalite to leuco-tonalite. The geochemical characteristics of low K- tholeiites, enrichment of large ion lithophile <span class="hlt">elements</span> (LILE), and depletion of HFSE in rocks of this plutonic complex are similar to those observed in the volcanic rocks of the IBM arc. The Ladakh batholith Complex is one of the granitic belts exposed north of the Indus-Tsangpo suture zone in Ladakh, representing calc-alkaline plutonism related to the subduction of the Neotethys floor in Late Cretaceous. This batholith comprises predominantly I-type granites with whole rock delta delta 18O values of 5.7-7.4 per mil, without major contribution from continental crustal material. We analyzed 22 trace <span class="hlt">elements</span> by ICP-MS, including Nb-Ta-Hf-Zr, in separated magnetites from five gabbros of the Tanzawa tonalite-gabbro complex and from three tonalitic gabbros of the Ladakh batholith. In NMORB normalized plots the trace <span class="hlt">element</span> patterns of all the magnetites analyzed show enrichment in Nb, Ta, Pb, Sr (5X NMORB) and Zr (2X NMORB) with characteristically high Nb/Ta and Zr/Hf ratios. In contrast, the patterns show anomalously low La, Ce, Pr, Nd, Sm and Hf concentrations (less than 0.1 NMORB). It is noteworthy that in the normalized trace <span class="hlt">element</span> plot, all the magnetites show high Nb/Ta ratios in contrast with high Ta/Nb ratios observed in typical arc magmas. These data support our hypothesis that magmatic crystallization of Fe-Ti oxides under high oxygen fugacity conditions during initial crystallization and formation of the Izu-Bonin and Ladakh-type arc batholiths may be the primary cause of depletion of the HFSE in later magmatic differentiates of less mafic and more felsic granitic arc rocks.</p> <div class="credits"> <p class="dwt_author">Basu, A. R.; Ghatak, A.; Arima, M.; Srimal, N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">367</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40777716"> <span id="translatedtitle">Partitioning of high field-strength and rare-<span class="hlt">earth</span> <span class="hlt">elements</span> between amphibole and quartz-dioritic to tonalitic melts: an experimental study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The knowledge of rare-<span class="hlt">earth</span> <span class="hlt">element</span> (REE) and high field-strength <span class="hlt">element</span> (HFSE) partitioning between minerals such as amphibole, pyroxenes or garnet and tonalitic liquids is essential to understand where and how tonalitic melts are generated. In this paper we present the results of trace-<span class="hlt">element</span> partitioning studies between amphibole and quartz-dioritic to tonalitic liquids which have been conducted at 1 GPa and</p> <div class="credits"> <p class="dwt_author">M Klein; H.-G Stosch; H. A Seck</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">368</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..1513403W"> <span id="translatedtitle">U-Pb ages and trace-<span class="hlt">element</span> <span class="hlt">geochemistry</span> of zircon from migmatite, Western Gneiss Region, Norway: significance for partial melting in continental subduction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The major rock type of the Western Gneiss Region (WGR), Norway, is migmatitic gneiss. This migmatite is the host rock to the well-studied ultrahigh-pressure (UHP) and high-pressure eclogites that were severely deformed during exhumation in an oblique divergent setting. To evaluate geochemical and age relationships between eclogite and host migmatite from peak to lower pressures, we obtained LA-ICP-MS U-Pb dates and trace-<span class="hlt">element</span> analyses for zircon from a variety of textural types of leucosome, from layer-parallel to crosscutting. Leucosome zircons are commonly euhedral, and many display oscillatory and sector zoning. Caledonian U-Pb zircon spot dates from zircon rim and near-rim regions are as old as 410-406 Ma, coeval with previously determined ages of UHP metamorphism of eclogite. Trace-<span class="hlt">element</span> analyses obtained simultaneously with U-Pb ages document zircon crystallization under garnet-stable conditions in the majority of leucosomes. Other zircons, including those from crosscutting pegmatite, yield younger ages (as young as 385 Ma), coinciding with ages determined for amphibolite-facies retrogression of eclogite; trace-<span class="hlt">element</span> analyses suggest that these zircons grew under plagioclase-stable (garnet-unstable) conditions. Combined age and trace-<span class="hlt">element</span> data for leucosome zircons track the transition from high-pressure (garnet-stable, plagioclase-unstable) crystallization to lower-pressure (plagioclase-stable) crystallization. If the euhedral zircons that yield ages coeval with peak or near-peak UHP metamorphism represent crystallization in anatectic leucosomes, these results, combined with field and petrographic observations, are consistent with the presence of partially molten crust in at least part of the WGR during continental subduction. The decreased viscosity and increased buoyancy and strain weakening associated with partial melting may have assisted the rapid ascent of rocks from mantle to crustal depths. Alternatively, exhumation of the UHP terrain in oblique divergence at plate tectonic rates may have triggered decompression melting from UHP to low- pressure conditions during ascent.</p> <div class="credits"> <p class="dwt_author">Whitney, Donna L.; Gordon, Stacia M.; Teyssier, Christian; Fossen, Haakon</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">369</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40778401"> <span id="translatedtitle">Evolution of the Ligurian Tethys in the Western Alps: Sm\\/Nd and U\\/Pb geochronology and rare-<span class="hlt">earth</span> <span class="hlt">element</span> <span class="hlt">geochemistry</span> of the Montgenèvre ophiolite (France)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We provide geochemical and geochronological data for gabbro, diorite and albitite samples from the Montgenèvre ophiolite in the Western Alps. This well-preserved remnant of the Piemont–Ligurian oceanic basin shows evidence of intra-oceanic deformation and metamorphism, but has suffered minor ductile deformation and metamorphism during the Alpine orogeny. The gabbros have geochemical features and initial Nd isotopic signatures similar to that</p> <div class="credits"> <p class="dwt_author">Sylvie Costa; Renaud Caby</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">370</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/13552839"> <span id="translatedtitle">Rare <span class="hlt">earth</span> <span class="hlt">element</span> <span class="hlt">geochemistry</span> and strontium isotopic composition of a massif-type anorthositic-charnockitic body: the Hidra Massif (Rogaland, SW Norway)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Hidra Massif (Rogaland Complex, SW Norway) mainly consists of plagioclase cumulates (anorthosites and leuconorites), which grade progressively into a fine-grained (200 m). locally porphyritic, jotunitic rock towards the contact with the granulite facies gneisses. The massif is cross-cut by thin (10 cm up to 1 m) charnockitic dykes. The petrographical and geochemical evolution of the Hidra Massif can be</p> <div class="credits"> <p class="dwt_author">Daniel Demaiffe; Jan Hertogen</p> <p class="dwt_publisher"></p> <p class="publishDate">1981-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">371</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFMPP13A1855S"> <span id="translatedtitle">High-resolution Carbon and Trace <span class="hlt">Element</span> <span class="hlt">Geochemistry</span> in Early-Middle Aptian Organic-Rich Sediments of the El Pui section, Cataluña, Spain</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Darker and more expanded layers characterize the interval of the El Pui section, Organyà Basin that correlates with the early-middle Aptian. They contrast with the earlier levels from the latest Barremian to the earliest Aptian interval, suggesting intensified OM sequestration in the superjacent layers. Accentuated conditions conducive to increased OM accumulation are revealed in the high-resolution ?13Corg curve that corroborates intensified primary productivity as seen elsewhere. Increasing trends in <span class="hlt">elemental</span> concentrations of Al, Si and Ti normalized with respect to TIC, further support the changing conditions and sustained transport of terrestrial material to the basin. Similarly, clay minerals results indicate intensified breakdown of continental rocks and rapid burial of clay. Enrichment of redox-sensitive trace <span class="hlt">elements</span> (Ni, V, Co, Cr, U, and Th) at certain levels attests that concurrent reducing conditions prevailed, culminating with temporal development of an anoxic phase. Microfacies characterized by rare to absent benthic fauna are in agreement with the geochemical results suggesting stressful bottom water conditions marked by oxygen deficiency. The integrated results thus indicate that existent intermittent oxygen-depleted conditions in sediments of the El Pui section became accentuated during the early Aptian leading to enhanced OM sequestration. Intensified global paleoceanographic and paleoclimatic changes in the early Aptian, superimposed on specific physiographic characteristics of the semi-enclosed basin and its adjacent landmasses, may have resulted in intensified nutrient delivery to the basin, increased productivity, and water column stratification that caused severe oxygen depletion.</p> <div class="credits"> <p class="dwt_author">Sanchez-Hernandez, Y.; Maurrasse, F. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">372</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.gm.univ-montp2.fr/spip/IMG/pdf/2003_Dhuime_alCRAS.pdf"> <span id="translatedtitle">C. R. Geoscience 335 (2003) 10811089 <span class="hlt">Geochemistry</span> (Isotope <span class="hlt">Geochemistry</span>)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">C. R. Geoscience 335 (2003) 1081­1089 <span class="hlt">Geochemistry</span> (Isotope <span class="hlt">Geochemistry</span>) An Early-Cambrian U this article: B. Dhuime et al., C. R. Geoscience 335 (2003). 2003 Académie des sciences. Published by Elsevier.crte.2003.09.012 #12;1082 B. Dhuime et al. / C. R. Geoscience 335 (2003) 1081­1089 ou d</p> <div class="credits"> <p class="dwt_author">Demouchy, Sylvie</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">373</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JAfES..68....1H"> <span id="translatedtitle">Multi-<span class="hlt">element</span> association analysis of stream sediment <span class="hlt">geochemistry</span> data for predicting gold deposits in Barramiya gold mine, Eastern Desert, Egypt</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The use of traditional statistical methods can provide suitable indicators of geochemical <span class="hlt">element</span> dispersion, and aids in targeting potential areas for mineral exploration. Analyzes of stream sediments from an ophiolite suite of ophiolitic mélange matrix and metasediments belt are used for regional geochemical prospecting of gold in the Barramiya mining district, Eastern Desert, Egypt. The principal rocks exposed in the study area are Late-Proterozoic volcano-sedimentary sequences intruded by serpentinite, small bodies of Older and Younger Granitoids, all injected by dykes of various compositions. Gold production derived mainly from shear zone with Au-bearing quartz veins hosted by ultramafic schists and serpentinites at fault intersections or along the basal décollement of the major thrusts, especially where granitoid massifs and stocks are common. Orebodies are mainly sulfide-bearing quartz and quartz-carbonate lodes associated with graphite-schist, listvenite and marble exposures, showing signs of structural control expressed in preferable orientation and consistent meso- and microfabrics. The area has two known gold deposits where several chromite mines are present. Auriferous veins are confined along E and ENE fracture systems and zones in a passive tectonic contact between the serpentinites and the metasediments. Results of 425 stream sediment samples from an area of ˜73 km2 analyzed for 13 trace <span class="hlt">elements</span> are presented using simple statistical and R-mode factor methods. The overall sample density achieved by the survey is ˜6 samples/km2. Significant variations in background metal contents are recorded near the known mineralized sites. Preliminary visual interpretation of individual spatial distribution patterns of Ag, As, Au, Cu, Mo, Pb, and W show clear-cut relationships with known gold mineralization in the study area. Geochemical patterns of these <span class="hlt">elements</span> delineate drainage basins with anomalous concentration of <span class="hlt">elements</span> genetically related to gold mineralization. Gold in analyzed samples ranges from <0.02 to 3.51 ppm with average 0.21 ppm. Most of the high <span class="hlt">element</span> concentrations in stream sediments are found in the graphite-schist and serpentinized marble rocks. Application of R-mode factor analysis indicates significant components of the sample composition. These reflect lithological, environmental and mineralization controls. Preparation of factor score map for the association Ag-Au-As-Cu-Zn-Pb-Mo-W enables a more precise delineation of zones of known gold mineralization as well as areas that may contain (on geological grounds) primary gold mineralization. The exploration significance of some anomalies has not been established, but a number of these anomalies may be related to undiscovered mineralization while others may be of no economic significance. Groundwater pH influences the hydromorphic dispersion patterns of Ag, As, and Au in different ways and this requires consideration during data interpretation.</p> <div class="credits"> <p class="dwt_author">Harraz, Hassan Z.; Hamdy, Mohamed M.; El-Mamoney, Mohamed H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">374</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014CSR....88..185W"> <span id="translatedtitle">The surface sediment types and their rare <span class="hlt">earth</span> <span class="hlt">element</span> characteristics from the continental shelf of the northern south China sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The grain size as well as some major and trace <span class="hlt">elements</span>, including rare <span class="hlt">earth</span> <span class="hlt">element</span> (REE), for 273 surface sediment samples collected from the continental shelf of the northern South China Sea were analyzed in this study. The sediment types are mainly sandy silt and silt, making up 60% of the whole samples, and secondly are mud, sandy mud, muddy sand and silty sand, making up 28% of the whole samples, based on grain-size in which the Folk's classification was used. The total REE content (?REE) show a wide variation from 21 ppm to 244 ppm with an average value of 155 ppm, which similar to the average ?REE of the China loess, but much different from that in deep-sea clay, showing a significant terrigenous succession. The REE contents in different sediment types vary greatly, mainly enriching in silt, sandy silt, mud and sandy mud. The REE distribution contours parallel to the coastal, presenting like strips and their contents gradually reduce with increasing distance from the coast. The high content of the western Pearl River Mouth, Shang/Xiachuan Islands and Hailing Bay might be regarded to the coastal current developed from the east to the west along to the Pearl River Mouth in the northern South China Sea. But the chondrite-normalized REE patterns in various sediment types have no difference, basically same as those of coastal rivers and upper crust. They all show relative enrichments in light rare <span class="hlt">earth</span> <span class="hlt">element</span> (LREE), noticeable negative Eu anomaly and no Ce anomaly, indicating that those sediments are terrigenous sediments and from the same source region. Further analysis suggest that the sedimentary environment in the study area is relatively stable and granite widely distributed in the South China mainland is the main source of REE, which are transported mainly by the Pearl River. The late diagenesis has little effect on the REE.</p> <div class="credits"> <p class="dwt_author">Wang, Shuhong; Zhang, Nan; Chen, Han; Li, Liang; Yan, Wen</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">375</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://wwwrcamnl.wr.usgs.gov/isoig/res/funda.html"> <span id="translatedtitle">Resources on Isotopes: Fundamentals of Stable Isotope <span class="hlt">Geochemistry</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This is a brief review of some of the fundamentals of stable isotope <span class="hlt">geochemistry</span>, including definitions, terminology, basic principles, standards, and guidelines on reporting data. Users can follow the link on the top right for the periodic table and read about the isotopic systems of several dozen <span class="hlt">elements</span>.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">376</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011APS..MARW33006S"> <span id="translatedtitle">Study of Defects That Trap Excitons in Yttrium Aluminum Garnets Doped With Rare-<span class="hlt">Earth</span> <span class="hlt">Elements</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Excitons play a fundamental role in transporting energy in photonic materials. Understanding and controlling excitons dynamics through their interactions with activating impurities and lattice defects is key to improving scintillation and optical properties. Singles crystals of yttrium aluminum garnet (YAG) crystals doped with rare-<span class="hlt">earths</span> were studied by positron annihilation, thermolunuinescence and optical spectroscopy. Evidence of defect complexes was found in the YAG structure. Positron lifetime measurements were performed to characterize those defects. Effects of dopants on the optical properties and lattice defects were investigated.</p> <div class="credits"> <p class="dwt_author">Selim, Farida; Varnery, Chris; Collins, Gary; McKay, David; Reda, Sherif</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">377</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19720018656&hterms=Tidal+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Tidal%2Bpower%2529"> <span id="translatedtitle">On the determination of the long period tidal perturbations in the <span class="hlt">elements</span> of artificial <span class="hlt">earth</span> satellites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The magnitude of the tidal effects depends upon the elastic properties of the <span class="hlt">earth</span> as described by Love numbers. The Love numbers appear as the coefficients in the expansion of the exterior tidal potential in terms of spherical harmonics (in Maxwellian form). A single averaging process was performed only along the parallels of latitude. This process preserves additional long period tidal effects (with periods of a few days or more). It also eliminates the short period effects with periods of one day or less.</p> <div class="credits"> <p class="dwt_author">Musen, P.; Felsentreger, T.</p> <p class="dwt_publisher"></p> <p class="publishDate">1972-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">378</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19750021843&hterms=beryllium+element&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dberyllium%252C%2Belement"> <span id="translatedtitle">Photoelectron emission analysis of surface <span class="hlt">elements</span> of the International Sun <span class="hlt">Earth</span> Explorer</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The photoemission was measured of engineering materials (aluminum; copper, plain; copper, abraded; copper-beryllium; magnesium; silver; In2O3 on silica; reflective coating on silica; teflon; kapton; and Pyre ML) associated with the International Sun <span class="hlt">Earth</span> Explorer (ISEE) Satellite. The procedures used are described, including the experimental equipment; results of the program, the conclusions reached, and areas for further work are presented. Data regarding the measured yield of the 11 materials whose surface emission was determined is included in the form of plots of photoelectric yield versus incident light wavelength.</p> <div class="credits"> <p class="dwt_author">Spencer, W. T.</p> <p class="dwt_publisher"></p> <p class="publishDate">1975-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">379</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JGRE..119..255O"> <span id="translatedtitle">Trace <span class="hlt">element</span> <span class="hlt">geochemistry</span> (Li, Ba, Sr, and Rb) using Curiosity's ChemCam: Early results for Gale crater from Bradbury Landing Site to Rocknest</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace <span class="hlt">elements</span> in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (<15 ppm). The lack of soil enrichment in Li, which is highly fluid mobile, is consistent with limited influx of subsurface waters contributing to the upper soils. Localized enrichments of up to ~60 ppm Li have been observed in several rocks but the host mineral for Li is unclear. Bathurst_Inlet is a fine-grained bedrock unit in which several analysis locations show a decrease in Li and other alkalis with depth, which may imply that the unit has undergone low-level aqueous alteration that has preferentially drawn the alkalis to the surface. Ba (~1000 ppm) was detected in a buried pebble in the Akaitcho sand ripple and it appears to correlate with Si, Al, Na, and K, indicating a possible feldspathic composition. Rb and Sr are in the conglomerate Link at abundances >100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace <span class="hlt">element</span> observations provide possible evidence of magma differentiation and aqueous alteration.</p> <div class="credits"> <p class="dwt_author">Ollila, Ann M.; Newsom, Horton E.; Clark, Benton; Wiens, Roger C.; Cousin, Agnes; Blank, Jen G.; Mangold, Nicolas; Sautter, Violaine; Maurice, Sylvestre; Clegg, Samuel M.; Gasnault, Olivier; Forni, Olivier; Tokar, Robert; Lewin, Eric; Dyar, M. Darby; Lasue, Jeremie; Anderson, Ryan; McLennan, Scott M.; Bridges, John; Vaniman, Dave; Lanza, Nina; Fabre, Cecile; Melikechi, Noureddine; Perrett, Glynis M.; Campbell, John L.; King, Penelope L.; Barraclough, Bruce; Delapp, Dorothea; Johnstone, Stephen; Meslin, Pierre-Yves; Rosen-Gooding, Anya; Williams, Josh</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">380</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40947308"> <span id="translatedtitle">Impulsive penetration of filamentary plasma <span class="hlt">elements</span> into the magnetospheres of the <span class="hlt">earth</span> and Jupiter</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Assuming that the solar wind plasma is usually nonuniform over distances of 10,000 km or less, it is shown that filamentary plasma <span class="hlt">elements</span> stretched out from the sun can penetrate impulsively and become engulfed into the magnetosphere. The diamagnetic effects associated with these plasma inhomogeneities are observed in outer magnetospheres and magnetosheaths as dips or directional discontinuities in the magnetic</p> <div class="credits"> <p class="dwt_author">J. Lemaire</p> <p class="dwt_publisher"></p> <p class="publishDate">1977-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_18");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">381</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42046178"> <span id="translatedtitle">Effects of continental insulation and the partitioning of heat producing <span class="hlt">elements</span> on the <span class="hlt">Earth</span>'s heat loss</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Continental lithosphere influences heat loss by acting as a local insulator to the convecting mantle and by sequestering heat-producing radioactive <span class="hlt">elements</span> from the mantle. Continental heat production can have a two-part effect since it decreases the amount of internal heat driving convection, which lowers mantle temperature, while also increasing the local insulating effect of continental lithosphere, which raises mantle temperature.</p> <div class="credits"> <p class="dwt_author">C. M. Cooper; A. Lenardic; L. Moresi</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p>