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1

Rare-earth element geochemistry of Madras granulites  

Microsoft Academic Search

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

Barry L. Weaver

1980-01-01

2

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

Microsoft Academic Search

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

Rachel A. Mills; Henry Elderfield

1995-01-01

3

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

4

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

Microsoft Academic Search

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

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

2006-01-01

5

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

NASA Astrophysics Data System (ADS)

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

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

1982-11-01

6

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

Microsoft Academic Search

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

Albert Günter Herrmann; Mark J. Potts; Doris Knake

1974-01-01

7

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

USGS Publications Warehouse

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

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

2007-01-01

8

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

Microsoft Academic Search

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

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

2006-01-01

9

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

Microsoft Academic Search

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

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

1982-01-01

10

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

11

Problems of Geochemistry.  

National Technical Information Service (NTIS)

Contents: Cosmochemistry and creation of the earth; Geochemistry of individual elements and isotopes; Genesis of rocks and geochemistry; Mineralogy and geochemistry; Geochemistry of the radioactive elements; Biogeochemistry; Geochemistry of the ocean; and...

N. I. Khitarov

1969-01-01

12

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

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

13

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

NASA Astrophysics Data System (ADS)

Rare-earth element (REE) analyses of 68 rock and mineral separate samples from the Samail ophiolite clearly differentiate the various units of the ophiolite suite and indicate that the crustal suite is cogenetic, produced by crystal fractionation of basaltic magma in a spreading ridge magma chamber. Mantle peridotites are residual in rare-earth character, but cannot be clearly related to the overlying mafic rocks. Chromian spinel is probably insignificant in its effect on REE distribution during partial melting and crystal fractionation, as indicated by the low REE concentrations in chromitite from the Samail. Layered gabbro REE patterns are dominated by cumulus clinopyroxene and plagioclase. Large positive Eu anomalies demonstrate plagioclase accumulation. Modal mixing (mass balance) calculations reveal that most of these adcumulus gabbros have REE patterns that are the products of the REE concentrations of their constituent cumulus phases in the observed modal proportions; hence no appreciable REE-rich mesostasis is present. Such calculations also allow the prediction of mineral REE concentrations not actually determined by mineral separate analyses. Several high-level (noncumulus?) gabbros yield patterns with positive Eu anomalies suggesting relative plagioclase accumulation, probably due to liquid fractionation (filter pressing). Dike complex REE patterns show light rare-earth element depletions and are similar to, but not necessarily diagnostic of, midocean ridge basalt. They cluster at similar abundance levels; however, the absolute variation in abundance is large, indicative of modification by crystal fractionation. Calculations using partition coefficient data indicate that many dikes represent liquids that could have existed in equilibrium with cumulus minerals of the plutonic suite. Mineral separate REE data from layered cumulus gabbro of the Khafifah stratigraphic section reveal cryptic variation trends that are correlated with major element variation, in support of a long-lived (periodically replenished) magma chamber model (Pallister and Hopson, 1978, 1979, 1981). (Cryptic variation as used herein is defined as the change in mineral composition with respect to stratigraphic position.) The REE cryptic variation shows both direct and inverse correlation to major element variation, indicating that magmatic replenishment was complicated by changes in parent melt REE abundance. A crystal fractionation origin for the small plagiogranite bodies of the Ibra area is favored by REE modeling, although larger bodies (Dasir) may also be related to magmatic inclusion of roofrock with diabase level REE distribution (Gregory and Taylor, 1979).

Pallister, John S.; Knight, Roy J.

1981-04-01

14

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

Microsoft Academic Search

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

R. C. Price; S. R. Taylor

1977-01-01

15

Rare-Earth Element, Lead, Carbon, and Nitrogen Geochemistry of Apatite-Bearing Metasediments from the ?3.8 Ga Isua Supracrustal Belt, West Greenland  

Microsoft Academic Search

We performed rare-earth element (REE) geochemistry and U-Pb geochronology on apatites in metasediments from the ?3.8 Ga Isua supracrustal belt (ISB) and Akilia Island, West Greenland, together with stepwise combustion isotopic investigation of carbon and nitrogen for the apatite-bearing quartz-magnetite BIF of uncontested sedimentary origin from northeastern ISB.Ion microprobe analyses reveal that apatites in psammitic schist from the ISB show

Manabu Nishizawa; Naoto Takahata; Kentaro Terada; Tsuyoshi Komiya; Yuichiro Ueno; Yuji Sano

2005-01-01

16

Rare earth element geochemistry of hydrothermal deposits from the active TAG Mound, 26{degrees}N mid-Atlantic ridge  

SciTech Connect

The rare earth element (REE) geochemistry of various phases from the active TAG hydrothermal mound has been examined and related to their mineralogy and fluid chemistry. The mound deposits range from black and white smoker chimneys, massive anhydrite/sulphide mixtures, oxides, and ochres. All phases, except black smoker chimney anhydrite, demonstrate a positive Eu anomaly when normalised to chondrite REE values. REE substitution into sulphide and sulphate phases appears to be strongly influenced by crystallographic control for all REE other than Eu. Precipitation of anhydrite within the TAG mound is the major mechanism for removal of REE during mound circulation and 0.15-0.35 g anhydrite is inferred to precipitate from every kg of fluid venting from the white smoker chimneys. Oxides from the mound fall into three different categories with distinct REE patterns: oxide rims on sulphides, atacamite-bearing oxides, and silica-rich Fe-oxides and ochres. The oxide rim phases contain sulphide and seawater derived REEs whereas the atacamite-bearing oxides and the ochreous material exhibit no seawater signature which suggests precipitation from, or alteration by, a modified hydrothermal fluid.

Mills, R.A. [Univ. of Southampton (United Kingdom); Elderfield, H. [Univ. of Cambridge (United Kingdom)

1995-09-01

17

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

18

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

NASA Astrophysics Data System (ADS)

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

Pazand, Kaveh; Javanshir, Ali Reza

2013-09-01

19

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

20

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

NASA Astrophysics Data System (ADS)

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

Ehya, Farhad

2012-01-01

21

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

Microsoft Academic Search

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

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

1996-01-01

22

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

Microsoft Academic Search

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

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

2005-01-01

23

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

Microsoft Academic Search

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

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

2009-01-01

24

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

Microsoft Academic Search

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

C. Pride; G. K. Muecke

1980-01-01

25

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

Microsoft Academic Search

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

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

2003-01-01

26

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

Microsoft Academic Search

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

Fenghua Zhao; Zhiyuan Cong; Hongfu Sun; Deyi Ren

2007-01-01

27

Trace-Element Geochemistry.  

ERIC Educational Resources Information Center

|Developments in this field during 1978 included four major meetings, two treatises on copper, one on arsenic, an assessment of mercury, and a book on "Modern Methods of Trace Element Analysis." (BB)|

Freedman, Jacob

1979-01-01

28

Rare earth element geochemistry of Late Devonian reefal carbonates, Canning Basin, Western Australia: confirmation of a seawater REE proxy in ancient limestones  

NASA Astrophysics Data System (ADS)

Rare earth element and yttrium (REE+Y) concentrations were determined in 49 Late Devonian reefal carbonates from the Lennard Shelf, Canning Basin, Western Australia. Shale-normalized (SN) REE+Y patterns of the Late Devonian samples display features consistent with the geochemistry of well-oxygenated, shallow seawater. A variety of different ancient limestone components, including microbialites, some skeletal carbonates (stromatoporoids), and cements, record seawater-like REE+Y signatures. Contamination associated with phosphate, Fe-oxides and shale was tested quantitatively, and can be discounted as the source of the REE+Y patterns. Co-occurring carbonate components that presumably precipitated from the same seawater have different relative REE concentrations, but consistent REE+Y patterns. Clean Devonian early marine cements ( n = 3) display REE+Y signatures most like that of modern open ocean seawater and the highest Y/Ho ratios (e.g., 59) and greatest light REE (LREE) depletion (average Nd SN/Yb SN = 0.413, SD = 0.076). However, synsedimentary cements have the lowest REE concentrations (e.g., 405 ppb). Non-contaminated Devonian microbialite samples containing a mixture of the calcimicrobe Renalcis and micritic thrombolite aggregates in early marine cement ( n = 11) have the highest relative REE concentrations of tested carbonates (average total REE = 11.3 ppm). Stromatoporoid skeletons, unlike modern corals, algae and molluscs, also contain well-developed, seawater-like REE patterns. Samples from an estuarine fringing reef have very different REE+Y patterns with LREE enrichment (Nd SN/Yb SN > 1), possibly reflecting inclusion of estuarine colloidal material that contained preferentially scavenged LREE from a nearby riverine input source. Hence, Devonian limestones provide a proxy for marine REE geochemistry and allow the differentiation of co-occurring water masses on the ancient Lennard Shelf. Although appropriate partition coefficients for quantification of Devonian seawater REE concentrations from out data are unknown, hypothetical Devonian Canning Basin seawater REE patterns were obtained with coefficients derived from modern natural proxies and experimental values. Resulting Devonian seawater patterns are slightly enriched in LREE compared to most modern seawaters and suggest higher overall REE concentrations, but are very similar to seawaters from regions with high terrigenous inputs. Our results suggest that most limestones should record important aspects of the REE geochemistry of the waters in which they precipitated, provided they are relatively free of terrigenous contamination and major diagenetic alteration from fluids with high, non-seawater-like REE contents. Hence, we expect that many other ancient limestones will serve as seawater REE proxies, and thereby provide information on paleoceanography, paleogeography and geochemical evolution of the oceans.

Nothdurft, Luke D.; Webb, Gregory E.; Kamber, Balz S.

2004-01-01

29

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

Microsoft Academic Search

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

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

1999-01-01

30

Geochemistry of rare earth elements in basalts from the Walvis Ridge: implications for its origin and evolution  

NASA Astrophysics Data System (ADS)

Selected basalts from a suite of dredged and drilled samples (IPOD sites 525, 527, 528 and 530) from the Walvis Ridge have been analysed to determine their rare earth element (REE) contents in order to investigate the origin and evolution of this major structural feature in the South Atlantic Ocean. All of the samples show a high degree of light rare earth element (LREE) enrichment, quite unlike the flat or depleted patterns normally observed for normal mid-ocean ridge basalts (MORBs). Basalts from Sites 527, 528 and 530 show REE patterns characterised by an arcuate shape and relatively low (Ce/Yb) N ratios (1.46-5.22), and the ratios show a positive linear relationship to Nb content. A different trend is exhibited by the dredged basalts and the basalts from Site 525, and their REE patterns have a fairly constant slope, and higher (Ce/Yb) N ratios (4.31-8.50). These differences are further reflected in the ratios of incompatible trace elements, which also indicate considerable variations within the groups. Mixing hyperbolae for these ratios suggest that simple magma mixing between a "hot spot" type of magma, similar to present-day volcanics of Tristan da Cunha, and a depleted source, possibly similar to that for magmas being erupted at the Mid-Atlantic Ridge, was an important process in the origin of parts of the Walvis Ridge, as exemplified by Sites 527, 528 and 530. Site 525 and dredged basalts cannot be explained by this mixing process, and their incompatible element ratios suggest either a mantle source of a different composition or some complexity to the mixing process. In addition, the occurrence of different types of basalt at the same location suggests there is vertical zonation within the volcanic pile, with the later erupted basalts becoming more alkaline and more enriched in incompatible elements. The model proposed for the origin and evolution of the Walvis Ridge involves an initial stage of eruption in which the magma was essentially a mixture of enriched and depleted end-member sources, with the N-MORB component being small. The dredged basalts and Site 525, which represent either later-stage eruptives or those close to the hot spot plume, probably result from mixing of the enriched mantle source with variable amounts and variable low degrees of partial melting of the depleted mantle source. As the volcano leaves the hot spot, these late-stage eruptives continue for some time. The change from tholeiitic to alkalic volcanism is probably related either to evolution in the plumbing system and magma chamber of the individual volcano, or to changes in the depth of origin of the enriched mantle source melt, similar to processes in Hawaiian volcanoes.

Humphris, Susan E.; Thompson, Geoffrey

1983-12-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

32

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

33

The aqueous geochemistry of the rare earth elements and yttrium. Part 7. REE, Th and U contents in thermal springs associated with the Idaho batholith  

Microsoft Academic Search

Concentrations of the rare earth elements (REE), Th and U have been determined in thermal waters emerging from a number of locations in and around the Idaho Batholith. Previous investigators have suggested that the source of heat for the geothermal systems studied is the radioactive decay of K, Th and U which are enriched in the rocks through which the

Paul E. van Middlesworth; Scott A. Wood

1998-01-01

34

Rare earth element geochemistry of sulphide weathering in the São Domingos mine area (Iberian Pyrite Belt): A proxy for fluid–rock interaction and ancient mining pollution  

Microsoft Academic Search

Gossan, disseminated orebody waste, other mining wastes, minesoils and acid mine drainage (AMD) in the abandoned São Domingos mine area (Iberian Pyrite Belt, IPB) have been analyzed for rare earth elements (REE). The main aim is to understand REE mobility during sulphide weathering so that the lanthanide series can be used both as a record of the water–rock interaction and

Rafael Pérez-López; Joaquín Delgado; José Miguel Nieto; Belén Márquez-García

2010-01-01

35

Geochemistry.  

ERIC Educational Resources Information Center

|Techniques in geochemistry continue to improve in sensitivity and scope. The exciting areas of geochemistry still include the classical fields of the origin of the elements and objects in space, but environmental crisis problems are important as well. (Author/BB)|

Fyfe, William S.

1979-01-01

36

Comparative Iodine Geochemistry of Earth and Mars: A Possible Biomarker  

Microsoft Academic Search

Iodine geochemistry on Earth is dominated by the actions of life, and thus may act as a biomarker on other planets. To begin to address this question we review our data on iodine in ALH84001 carbonate and Nakhla and outline some areas for future research.

J. D. Gilmour; J. A. Whitby; G. Turner

1999-01-01

37

Rare earth element geochemistry of acid-sulphate and acid-sulphate-chloride geothermal systems from Yellowstone National Park, Wyoming, USA  

SciTech Connect

Rare earth element (REE) concentrations have been determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in acid-sulphate and acid-sulphate-chloride waters and the associated sinters and volcanic rocks from the Yellowstone National Park (YNP), Wyoming, USA, geothermal system. REE concentrations in the volcanic rocks range from 222 to 347 ppm: their chondrite-normalised REE patterns are typical of upper continental crust, with LREE > HREE and negative Eu anomalies. Total REE concentrations in the fluids range from 3 to 1133 nmol kg{sup -1} ({ge}162 ppm), and {Sigma}REE concentrations in sinter are {ge}181 ppm. REE abundances and patterns in drill core material from YNP indicate some REE mobility. Relative to the host rocks the REE patterns of the fluids are variably depleted in HREEs and LREEs, and usually have a pronounced positive Eu anomaly. This decoupling of Eu from the REE suite suggests that (1) Eu has been preferentially removed either from the host rock glass or from the host rock minerals, or (2) the waters are from a high temperature or reducing environment where Eu{sup 2+} is more soluble than the trivalent REEs. Since the latter is inconsistent with production of acid-sulphate springs in a low temperature, oxidising near-surface environment, we suggest that the positive Eu anomalies in the fluids result from preferential dissolution of a Eu-rich phase in the host rock. Spatial and temporal variations in major element chemistry and pH of the springs sampled from Norris Geyser Basin and Crater Hills accompany variations in REE concentrations and patterns of individual geothermal springs. These are possibly related to changes in subsurface plumbing, which results in variations in mixing and dilution of the geothermal fluids and may have lead to changes in the extent and nature of REE complexing. 37 refs., 7 figs., 4 tabs.

Lewis, A.J.; Palmer, M.R.; Kemp, A.J. [Bristol Univ. (United Kingdom); Sturchio, N.C. [Argonne National Lab., IL (United States)

1997-02-01

38

Behavior of Rare Earth Elements in Fractured Aquifers  

Microsoft Academic Search

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

S. Lee; Y. Kim; K. Lee

2003-01-01

39

Rare earth element and Nd isotope geochemistry of an ombrotrophic peat bog at Karukinka (Chile, 53.9° S): a palaeo-record of Holocene dust deposition in Tierra del Fuego.  

NASA Astrophysics Data System (ADS)

The value of ombrotrophic peat bogs as past atmospheric dust records, has been increasingly recognized over the past 10 years. Their high accumulation rates provide high resolution archives of natural atmospheric dust deposition since the Late Glacial, often missing in marine, lake and ice core records. Consequently, peat deposits can be used as a proxy for atmospheric circulation patterns and thus palaeoclimate. In the Southern Hemisphere, the climate is considered to be driven by the Southern Westerly Wind belt (SSW), as it significantly affects the Antarctic Circumpolar Current and hence atmospheric CO2 levels. Palaeo SSW belt migrations have been observed in palaeoclimate records but, reconstructions of SSW shifts and associated climatic changes are incoherent, in particular for the Holocene. As peatlands thrive in southwest Tierra del Fuego due to its high annual precipitation, a remote ombrotrophic peat bog at Karukinka (southwest on the Isla Grande de Tierra del Fuego) was sampled, to investigate the Holocene palaeoclimate in southern South America based on dust deposition records. A 4,5 m long Russian D-core was recovered and subsequently subsampled for elemental and isotope geochemistry in addition to density and radiocarbon dating measurements. Initial results show a number of layers enriched in scandium, indicating the presence of lithogenic material, i.e. dust. Rare earth element patterns indicate at least 2 different sources. The most significant dust peak occurs at the base of the core at ~7300 Cal years B.P and has a neodymium isotopic composition of 2.2, suggesting a volcanic origin.

Vanneste, Heleen; De Vleeschouwer, François; Vanderstraeten, Aubry; Mattielli, Nadine; Triquet, Delphine; Piotrowska, Natalia; Le Roux, Gael

2013-04-01

40

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

41

Chemical weathering in Malay Peninsula and North Borneo: Clay mineralogy and element geochemistry of river surface sediments  

Microsoft Academic Search

Weathering products of silicate rocks are particularly useful for evaluating the continental chemical weathering on the Earth’s\\u000a surface and its mechanism. Clay mineralogy and major-element geochemistry of surface sediment samples collected in major rivers\\u000a of Malay Peninsula and North Borneo in the tropical Southeast Asian region are used to study the present chemical weathering\\u000a process and its controlling factors of

Hao Wang; ZhiFei Liu; Edlic Sathiamurthy; Christophe Colin; JianRu Li; YuLong Zhao

2011-01-01

42

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

43

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

Microsoft Academic Search

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

Baohong Hou; Dong Pu Zhao

1999-01-01

44

Geochemistry  

ERIC Educational Resources Information Center

|Enumerates some of the research findings in geochemistry during the last year, including X-ray analysis of the Mars surface, trace analysis of fresh and esterarine waters, and analysis of marine sedements. (MLH)|

Ailin-Pyzik, Iris B.; Sommer, Sheldon E.

1977-01-01

45

Simulating processes within the Earth: experimental geochemistry at ORNL  

Microsoft Academic Search

An understanding of the chemical processes operating within the earth is heavily dependent on the ability to simulate, through experimental or theoretical means, deep-earth conditions currently inaccessible to study. Analogue studies of simplified geological systems, or experiments that model the natural systems, have been the focus of the geosciences research program at ORNL for the past six years. The principal

1984-01-01

46

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

47

The rare earth elements in seawater  

Microsoft Academic Search

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

Henry Elderfield; Mervyn J. Greaves

1982-01-01

48

Toward a unified science of the Earth's surface: Opportunities for synthesis among hydrology, geomorphology, geochemistry, and ecology  

Microsoft Academic Search

The Earth's surface is shaped by the interaction of tectonics, water, sediment, solutes, and biota over a wide range of spatial and temporal scales and across diverse environments. Development of a predictive science of Earth surface dynamics integrates many disciplines and approaches, including hydrology, geomorphology, ocean and atmospheric science, sedimentary and structural geology, geochemistry, and ecology. This paper discusses challenges,

Chris Paola; Efi Foufoula-Georgiou; William E. Dietrich; Miki Hondzo; David Mohrig; Gary Parker; Mary E. Power; Ignacio Rodriguez-Iturbe; Vaughan Voller; Peter Wilcock

2006-01-01

49

Archean granulite gneisses from eastern Hebei Province, China: rare earth geochemistry and tectonic implications  

Microsoft Academic Search

The granulite gneisses and their retrograded products of the Qianxi Group from eastern Hebei Province, China, have been investigated for their isotope and trace element geochemistry. A consistent age of about 2.5 AE has been obtained by the Rb-Sr and Sm-Nd whole-rock isochron methods, in agreement with the zircon U-Pb data (Pidgeon 1980; D.Y. Liu, unpubl.). Geochemical arguments from initial

Bor-Ming Jahn; Zong-Qing Zhang

1984-01-01

50

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

51

Principles of Geochemistry.  

National Technical Information Service (NTIS)

Contents: Geochemistry, its limitations and functions methods and history of development; Structure and composition of the earth and the earth's crust, including the hydrosphere and atmosphere; Geochemistry of isotopes; The structure and size of atoms and...

V. V. Shcherbina

1977-01-01

52

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

53

Chemical weathering in Luzon, Philippines from clay mineralogy and major-element geochemistry of river sediments  

Microsoft Academic Search

Clay mineralogy and major-element geochemistry of 35 surface sediment samples collected in 21 major to moderate rivers of Luzon, Philippines are used to evaluate the present chemical weathering process. The clay mineral assemblage consists mainly of smectite (average 86%) with minor kaolinite (9%) and chlorite (5%) and very scarce illite (1%), and does not show strong island-wide differences. The major

Zhifei Liu; Yulong Zhao; Christophe Colin; Fernando P. Siringan; Qiong Wu

2009-01-01

54

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

Microsoft Academic Search

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

Aicheng Zhang; Weibiao Hsu

2009-01-01

55

The Role of the Ion Microprobe in Solid-Earth Geochemistry  

NASA Astrophysics Data System (ADS)

Despite the early success of the electron microprobe in taking petrology to the micron scale, and the widespread use of mass spectrometers in geochemistry and geochronology, it was not until the mid-1970s that the ion microprobe came into its own as an in situ analytical tool in the Earth sciences. Despite this inauspicious beginning, secondary ion mass spectrometry (SIMS) was widely advertised as a technology that would eventually eclipse thermal ion mass spectrometry (TIMS) in isotope geology. However this was not to happen. While various technical issues in SIMS such as interferences and matrix effects became increasingly clear, an appreciation grew for the complimentary abilities of SIMS and TIMS that, even with the advent of ICP-MS, continues to this day. Today the ion microprobe is capable of abundance measurements in the parts-per-billion range across nearly the entire periodic table, and SIMS stable isotope data quality is now routinely crossing the 1 per mil threshold, all at the micron scale. Much of this success is due to the existence of multi-user community facilities for SIMS research, and the substantial efforts of interested scientists to understand the fundamentals of sputtered ion formation and their application to geochemistry. Recent discoveries of evidence for the existence of ancient crust and oceans, the emergence of life on Earth, the large-scale cycling of surficial materials into the deep Earth, and illumination of fundamental high-pressure phenomena have all been made possible by SIMS, and these (and many more) discoveries owe a debt to the vision of creating and supporting multi-user community facilities for SIMS. The ion microprobe remains an expensive instrument to purchase and maintain, yet it is also exceedingly diverse in application. Major improvements in SIMS, indeed in all mass spectrometry, are visible on the near horizon. Yet the geochemical community cannot depend on commercial manufacturers alone to design and build the next generation of instrumentation for geochemistry. Such will be the role of instrument-minded scientists asking questions that simply cannot be answered by extant means. And it will be multi-user facilities that will make such advancements available to the wider geochemical community.

Hauri, E. H.

2002-12-01

56

Rare earth element systematics in hydrothermal fluids  

NASA Astrophysics Data System (ADS)

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

Michard, Annie

1989-03-01

57

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

58

Rare earth elements in alpine peridotites  

Microsoft Academic Search

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

M. Loubet; N. Shimizu; C. J. Allègre

1975-01-01

59

Rare earth element systematics in hydrothermal fluids  

Microsoft Academic Search

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

Annie Michard

1989-01-01

60

Behavior of Rare Earth Elements in Fractured Aquifers  

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

61

Rare Earth Element Contents of High pCO 2 Groundwaters of Primorye, Russia: Mineral Stability and Complexation Controls  

Microsoft Academic Search

The rare earth element (REE) geochemistry of cold, high pCO2 groundwaters was studied in springs and boreholes in the Primorye region of the Russian Far East. The gas phase in these\\u000a waters is dominated by mantle-derived CO2 (up to 2.6 atm.), being introduced to shallow groundwaters along major fault systems. The aggressive nature of these moderately\\u000a acidic groundwaters has led

Paul Shand; Karen H. Johannesson; Oleg Chudaev; Valentina Chudaeva; W. Mike Edmunds

62

Orientations in Geochemistry.  

National Technical Information Service (NTIS)

An effort is made to provide a useful description of the growing field of geochemistry, its scope and potential. The report presents an assessment of current work in geochemistry, analyzes its interrelationships with the other earth and planetary sciences...

1974-01-01

63

Volatile and lithophile trace-element geochemistry of Mexican tin rhyolite magmas deduced from melt inclusions  

Microsoft Academic Search

We have investigated the petrology and geochemistry of whole rocks from two small-volume, Sn- and F-mineralized rhyolitec dome complexes of the Mexican tin rhyolite belt, Cerro el Lobo and Cerro el Pajaro, to determine volcanic degassing and mineralizing processes in felsic igneous systems. The abundance and distribution of volatiles (H2O, B, F, and Cl) and lithophile trace and ore elements

James D. Webster; Donald M. Burt; R. A. Aguillon

1996-01-01

64

Trace element geochemistry of marine biogenic particulate matter  

SciTech Connect

Plankton samples were investigated for physical and chemical leaching decomposition to identify the major and trace element composition of particulate carrier phases. The identification of trace element/major element ratios in the biogenic materials was emphasized. The majority of the trace elements in the samples were directly associated with the nonskeletal organic phases of the plankton. Calcium carbonate and opal were not significant carriers for any of the trace elements studied. A refractory phase containing Al and Fe in terrigenous ratios was present in all samples, even from the more remote marine locations.

Collier, R.W.

1981-02-01

65

Anthropogenic Cycles of Rare Earth Elements  

NASA Astrophysics Data System (ADS)

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

Du, X.; Graedel, T. E.

2009-12-01

66

Tipping elements in the Earth's climate system  

SciTech Connect

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

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

2008-02-12

67

Trace elements geochemistry of the Dobrudza coal basin, Bulgaria  

Microsoft Academic Search

The paper discusses the abundance, mode of occurrence and origin of trace elements in the Dobrudza coal deposit. The deposit is the deepest in Bulgaria - it is overburden by Paleozoic up to Cenozoic sediments of 1300 m to 1600 m thickness. The coal rank reaches the stage of high volatile A bituminous coal.The contents of Ba, Cl, Br, Mn, Ge, Pb,

Greta M. Eskenazy

2009-01-01

68

Trace element geochemistry in the upper Amazon drainage basin (Bolivia)  

Microsoft Academic Search

The distribution of trace elements (Sr, Mo, Ba, Rb, U, Mn, Ni, Cu, Zn, and Cd) was investigated in surface waters and associated particulates in two upper Amazonian basins (Mamore and Beni). Dissolved Sr, Ba, Mo, Rb, U and to a lesser extent Zn and Cd correlate with major ions and appear to be predominantly derived from soluble rocks (carbonates,

Françoise Elbaz-Poulichet; Patrick Seyler; Laurence Maurice-Bourgoin; Jean-Loup Guyot; Claude Dupuy

1999-01-01

69

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

National Technical Information Service (NTIS)

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

R. P. Elliott

1964-01-01

70

Early developments in petroleum geochemistry  

Microsoft Academic Search

Petroleum geochemistry is the outgrowth of the application of the principles and methods of organic chemistry to petroleum refining and petroleum geology. This paper reviews 120 years of petroleum geochemistry, from about 1860 to 1980, and includes a discussion of the formal recognition of petroleum geochemistry as an earth-science discipline starting in 1959 when a general petroleum geochemistry symposium was

John M. Hunt; R. Paul Philp; Keith A. Kvenvolden

2002-01-01

71

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

Microsoft Academic Search

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

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

2001-01-01

72

SEPARATION OF RARE EARTH ELEMENTS BY FOCUSSING CHROMATOGRAPHY  

Microsoft Academic Search

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

Y. Kamemoto; K. Hagiya; S. Yamagishi

1963-01-01

73

Concentration of rare earth elements in five ordinary chondrites  

Microsoft Academic Search

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

Kolesov

1974-01-01

74

Rare earth elements in natural calcite  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

75

Evidence against a chondritic Earth.  

PubMed

The (142)Nd/(144)Nd ratio of the Earth is greater than the solar ratio as inferred from chondritic meteorites, which challenges a fundamental assumption of modern geochemistry--that the composition of the silicate Earth is 'chondritic', meaning that it has refractory element ratios identical to those found in chondrites. The popular explanation for this and other paradoxes of mantle geochemistry, a hidden layer deep in the mantle enriched in incompatible elements, is inconsistent with the heat flux carried by mantle plumes. Either the matter from which the Earth formed was not chondritic, or the Earth has lost matter by collisional erosion in the later stages of planet formation. PMID:22460899

Campbell, Ian H; O'Neill, Hugh St C

2012-03-28

76

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

77

On the occurrence, trace element geochemistry, and crystallization history of zircon from in situ ocean lithosphere  

NASA Astrophysics Data System (ADS)

We characterize the textural and geochemical features of ocean crustal zircon recovered from plagiogranite, evolved gabbro, and metamorphosed ultramafic host-rocks collected along present-day slow and ultraslow spreading mid-ocean ridges (MORs). The geochemistry of 267 zircon grains was measured by sensitive high-resolution ion microprobe-reverse geometry at the USGS-Stanford Ion Microprobe facility. Three types of zircon are recognized based on texture and geochemistry. Most ocean crustal zircons resemble young magmatic zircon from other crustal settings, occurring as pristine, colorless euhedral (Type 1) or subhedral to anhedral (Type 2) grains. In these grains, Hf and most trace elements vary systematically with Ti, typically becoming enriched with falling Ti-in-zircon temperature. Ti-in-zircon temperatures range from 1,040 to 660°C (corrected for a TiO2 ? 0.7, a SiO2 ? 1.0, pressure ? 2 kbar); intra-sample variation is typically ~60-150°C. Decreasing Ti correlates with enrichment in Hf to ~2 wt%, while additional Hf-enrichment occurs at relatively constant temperature. Trends between Ti and U, Y, REE, and Eu/Eu* exhibit a similar inflection, which may denote the onset of eutectic crystallization; the inflection is well-defined by zircons from plagiogranite and implies solidus temperatures of ~680-740°C. A third type of zircon is defined as being porous and colored with chaotic CL zoning, and occurs in ~25% of rock samples studied. These features, along with high measured La, Cl, S, Ca, and Fe, and low (Sm/La)N ratios are suggestive of interaction with aqueous fluids. Non-porous, luminescent CL overgrowth rims on porous grains record uniform temperatures averaging 615 ± 26°C (2SD, n = 7), implying zircon formation below the wet-granite solidus and under water-saturated conditions. Zircon geochemistry reflects, in part, source region; elevated HREE coupled with low U concentrations allow effective discrimination of ~80% of zircon formed at modern MORs from zircon in continental crust. The geochemistry and textural observations reported here serve as an important database for comparison with detrital, xenocrystic, and metamorphosed mafic rock-hosted zircon populations to evaluate provenance.

Grimes, Craig B.; John, Barbara E.; Cheadle, Michael J.; Mazdab, Frank K.; Wooden, Joseph L.; Swapp, Susan; Schwartz, Joshua J.

2009-12-01

78

Trace-element geochemistry of coal resource development related to environmental quality and health  

SciTech Connect

This report assesses for decision makers and those involved in coal resource development the environmental and health impacts of trace-element effects arising from significant increases in the use of coal, unless unusual precautions are invoked. Increasing demands for energy and the pressing need for decreased dependence of the United States on imported oil require greater use of coal to meet the nation's energy needs during the next decade. If coal production and consumption are increased at a greatly accelerated rate, concern arises over the release, mobilization, transportation, distribution, and assimilation of certain trace elements, with possible adverse effects on the environment and human health. It is, therefore, important to understand their geochemical pathways from coal and rocks via air, water, and soil to plants, animals, and ultimately humans, and their relation to health and disease. To address this problem, the Panel on Trace Element Geochemistry of Coal Resource Development Related to Health (PECH) was established. Certain assumptions were made by the Panel to highlight the central issues of trace elements and health and to avoid unwarranted duplication of other studies. Based on the charge to the Panel and these assumptions, this report describes the amounts and distribution of trace elements related to the coal source; the various methods of coal extraction, preparation, transportation, and use; and the disposal or recycling of the remaining residues or wastes. The known or projected health effects are discussed at the end of each section.

Not Available

1980-01-01

79

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

80

Rare earth elements in the Amazon basin  

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

81

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

82

Rare earth elements in soil and plant systems - A review  

Microsoft Academic Search

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

Germund Tyler

2004-01-01

83

Trace Rare Earth Element Analysis in Briny Groundwaters.  

National Technical Information Service (NTIS)

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

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

1986-01-01

84

Archean granulite gneisses from eastern Hebei Province, China: rare earth geochemistry and tectonic implications  

NASA Astrophysics Data System (ADS)

The granulite gneisses and their retrograded products of the Qianxi Group from eastern Hebei Province, China, have been investigated for their isotope and trace element geochemistry. A consistent age of about 2.5 AE has been obtained by the Rb-Sr and Sm-Nd whole-rock isochron methods, in agreement with the zircon U-Pb data (Pidgeon 1980; D.Y. Liu, unpubl.). Geochemical arguments from initial isotopic ratios (ISr and INd) and elemental distribution patterns have led us to conclude that this age of about 2.5 AE represents the time of granulite facies metamorphism, which must have followed closely the primary emplacement of their protoliths. Previous claims for early Archean ages (>3.5 AE) of these granulites are not substantiated. The mineral isotope systematics register an important thermal event at about 1.7 AE, roughly corresponding to the time of the widespread Luliang Orogeny (Ma and Wu 1981) or Chungtiao Movement (Huang 1978). The granulites of the Qianxi Group have diverse compositions ranging from ultrabasic through basic-intermediate to acid. Discriminant function calculations suggest that most analyzed samples have igneous parentage. Only a few show characteristics of metasedimentary rocks. The igneous protoliths apparently belong to two series — tholeiitic and calc-alkaline, with the latter dominating in abundance. The majority of the acid granulites have compositions corresponding to tonalite-granodiorite. Except for ultrabasic and metasedimentary rocks, all REE patterns are significantly fractionated with LREE enrichment. The degree of fractionation, as measured by the (La/Yb)N ratios, is most important in the acid granulites. These rocks often show positive Eu anomalies and HREE depletions that are typical of Archean TTG rocks (tonalitetrondhjemite-granodiorite). The existence of komatiites has been previously reported in this region. Although a few rocks have a major element chemistry similar to that for peridotitic komatiites, the lack of associated members in a komatiitic series and the scarcity of REE data have not confirmed the true komatiite occurrence in this region. Many Qianxi granulites are highly depleted in Rb relative to K and Sr. This preferential Rb depletion during granulite facies metamorphism has led to very high K/Rb and very low Rb/Sr ratios. The most comparable case is found in Lewisian granulites. Although the fractionated REE patterns of the basic granulites somewhat resemble those of continental flood basalts, the highly different abundances in other incompatible elements (Ti, Zr, and Ba) readily distinguish them from each other. Nevertheless, the LREE enriched patterns of the basic granulites may suggest an origin of their protoliths by partial melting of LREE-enriched mantle sources. On the other hand, the REE patterns of acid granulites suggest that their protoliths could be derived by partial melting of quartz eclogite, amphibolite or basic granulite. The close time relationship for a series of geologic events, namely, from initial melting of mantle peridotites, through fractional crystallisation of basaltic magmas, to granulite facies metamorphism, seems to occur in many granulite terrains. This relationship, together with the juxtaposition of lithologies of different origins and the exceptionally high pressure conditions (>10 Kb) can be best explained by crustal underplating combined with intracrustal thin-skinned thrusting and stacking of crustal slices. The “andesitic or island arc” model for the formation of the lower continental crust is not in good agreement with the present geochemical data.

Jahn, Bor-Ming; Zhang, Zong-Qing

1984-03-01

85

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

86

The Oceanic Chemistry of the Rare-Earth Elements  

Microsoft Academic Search

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

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

1988-01-01

87

Origins and early evolution of volatile elements in Earth  

Microsoft Academic Search

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

B. Marty

2009-01-01

88

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

National Technical Information Service (NTIS)

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

C. Hurst

2010-01-01

89

Trace-element geochemistry of postorogenic granites from the northeastern Arabian Shield, Kingdom of Saudi Arabia  

USGS Publications Warehouse

Concentrations determined for all of the trace elements included in this study of postorogenic granites from the northeastern Arabian Shield are best described by log-normal distributions. The trace elements are divided into two groups: (1) compatible lithophile and siderophile elements (strontium, cobalt, scandium, manganese, europium, and titanium) and (2) incompatible lithophile elements (uranium, thorium, tantalum, rubidium, and rare-earth elements, except europium). The compatible elements exhibit greatest concentrations in the metaluminous postorogenic granites, and concentrations decrease with increasing degree of magma evolution. Economic potential for these elements and other geochemically similar elements is considered to be low. The concentrations of the incompatible elements increase with increasing degree of magma evolution and are greatest in the peralkaline and peraluminous granites. There is some geologic evidence that pegmatite and vein-forming processes were operative toward the end stage of postorogenic magmatism in the northeastern Arabian Shield, and therefore there is some probability for economic potential for these elements. It is suggested that such potential is greatest where highly evolved postorogenic granites intruded volatile (generally water )-rich country rocks.

Stuckless, John S.; Knight, R. J.; VanTrump, G.; Budahn, J. R.

1983-01-01

90

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

91

Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites  

Microsoft Academic Search

All samples studied here exhibit low ?Nd (lamproites; Western Australia = -10 to -19.2 and Smoky Butte = -21.6 to -25.9: Group II kimberlites: Finsch Mine = -5.8 to -7.4) and (87Sr\\/86Sr)i > Bulk Earth. They are all LREE enriched (up to 1000 × chondrite) and have high trace element contents (i.e. Rb, Rb, Ba, Th, K, Ta, Sr, P,

K. J. Fraser; C. J. Hawkesworth; A. J. Erlank; R. H. Mitchell; B. H. Scott-Smith

1985-01-01

92

The Oxygen Isotope and Elemental Geochemistry of Archean Rocks From Northern Ontario  

Microsoft Academic Search

The oxygen isotope and chemical compositions (including rare earth elements) of Archean rocks from northern Ontario have been interpreted in terms of various magmatic, sedimentary, metamorphic and\\/or alteration processes that have occurred during the history of these samples.\\u000aThe greenschist facies clastic metasedimentary rocks from the Wabigoon, Abitibi, and Uchi granite-greenstone belts have chemical compositions that indicate derivation from dominantly

Frederick John Longstaffe

1977-01-01

93

Sulfide Mineralogy and Geochemistry  

NASA Astrophysics Data System (ADS)

Reviews in Mineralogy and Geochemistry Series, Volume 61 David J. Vaughan, Editor Geochemical Society and Mineralogical Society of America; ISBN 0-939950-73-1 xiii + 714 pp.; 2006; $40. Sulfide minerals as a class represent important minor rock-forming minerals, but they are generally known as the chief sources of many economic metallic ores. In the past two decades, sulfide research has been extended to include important roles in environmental geology of sulfide weathering and resultant acid mine drainage, as well as in geomicrobiology in which bacteria make use of sulfides for metabolic energy sources. In the latter respect, sulfides played an important role in early evolution of life on Earth and in geochemical cycling of elements in the Earth's crust and hydrosphere.

Dilles, John

2007-02-01

94

Removal of rare earth elements by algal flagellate Euglena gracilis  

Microsoft Academic Search

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

Nobuyoshi Ishii; Keiko Tagami; Shigeo Uchida

2006-01-01

95

Stabilisation of divalent rare earth elements in natural fluorite  

Microsoft Academic Search

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

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

2002-01-01

96

RARE EARTH ELEMENT SENSITIVITY FACTORS IN CALCIC PLAGIOCLASE (ANORTHITE)  

Microsoft Academic Search

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

C. Floss; B. Jolliff

97

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

Microsoft Academic Search

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

H. C. Urey

1953-01-01

98

Rare Earth Elements in CI1-Chondrites and Planetary Samples  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

99

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

National Technical Information Service (NTIS)

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

J. C. Laul E. A. Lepel

1986-01-01

100

Rare earth elements as a fingerprint of soil components solubilization  

Microsoft Academic Search

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

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

2009-01-01

101

Ternary phosphates of rubidium-cesium-rare earth element  

Microsoft Academic Search

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

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

1986-01-01

102

Rare Earth Element Evidence for Paleolake Chemistry  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

103

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

NASA Astrophysics Data System (ADS)

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

Webb, Gregory E.; Kamber, Balz S.

2000-05-01

104

Rare earth element partition coefficients in zircon/melt systems  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

105

Interactions of rare earth elements with bacteria and organic ligands  

Microsoft Academic Search

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

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

2006-01-01

106

Experimental evidence of rare earth element immobility in greenstones  

Microsoft Academic Search

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

Martin Menzies; William Seyfried; Douglas Blanchard

1979-01-01

107

Energy-adjusted pseudopotentials for the rare earth elements  

Microsoft Academic Search

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

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

1989-01-01

108

Ion probe measurement of rare earth elements in biogenic phosphates  

SciTech Connect

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

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

1989-12-01

109

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

110

Apollo 15 Lunar Impact Glasses: Geochemistry, Age, and the Earth-Moon Bombardment  

NASA Astrophysics Data System (ADS)

Lunar impact glasses from the Apollo 15 landing site provide information about the rate of impacts in the Earth-Moon system. Geochemical and age data, in the context of the landing site and in concert with other lunar data, will be presented.

Zellner, N. E. B.; Norman, M. D.

2012-09-01

111

Volatile and lithophile trace-element geochemistry of Mexican tin rhyolite magmas deduced from melt inclusions  

Microsoft Academic Search

We have investigated the petrology and geochemistry of whole rocks from two small-volume, Sn- and F-mineralized rhyolitec dome complexes of the Mexican tin rhyolite belt, Cerro el Lobo and Cerro el Pajaro, to determine volcanic degassing and mineralizing processes in felsic igneous systems. The abundance and distribution of volatiles (H 2 O, B, F, and Cl) and lithophile trace and

James D. Webster; Donald M. Burt; R. A. Aguillon

1996-01-01

112

Evidence from Sardinian basalt geochemistry for recycling of plume heads into the Earth's mantle.  

PubMed

Up to 10 per cent of the ocean floor consists of plateaux--regions of unusually thick oceanic crust thought to be formed by the heads of mantle plumes. Given the ubiquitous presence of recycled oceanic crust in the mantle source of hotspot basalts, it follows that plateau material should also be an important mantle constituent. Here we show that the geochemistry of the Pleistocene basalts from Logudoro, Sardinia, is compatible with the remelting of ancient ocean plateau material that has been recycled into the mantle. The Sr, Nd and Hf isotope compositions of these basalts do not show the signature of pelagic sediments. The basalts' low CaO/Al2O3 and Ce/Pb ratios, their unradiogenic 206Pb and 208Pb, and their Sr, Ba, Eu and Pb excesses indicate that their mantle source contains ancient gabbros formed initially by plagioclase accumulation, typical of plateau material. Also, the high Th/U ratios of the mantle source resemble those of plume magmas. Geochemically, the Logudoro basalts resemble those from Pitcairn Island, which contain the controversial EM-1 component that has been interpreted as arising from a mantle source sprinkled with remains of pelagic sediments. We argue, instead, that the EM-1 source from these two localities is essentially free of sedimentary material, the geochemical characteristics of these lavas being better explained by the presence of recycled oceanic plateaux. The storage of plume heads in the deep mantle through time offers a convenient explanation for the persistence of chemical and mineralogical layering in the mantle. PMID:11130068

Gasperini, D; Blichert-Toft, J; Bosch, D; Del Moro, A; Macera, P; Télouk, P; Albarède, F

2000-12-01

113

Trace element and isotope geochemistry of geothermal fluids, East Rift Zone, Kilauea, Hawaii  

NASA Astrophysics Data System (ADS)

A research program has been undertaken in an effort to better characterize the composition and the precipitation characteristic of the geothermal fluids produced by the HGP-A geothermal well located on the Kilauea East Rift Zone on the island of Hawaii. The results of these studies have shown that the chemical composition of the fluids changed over the production life of the well and that the fluids produced were the result of the mixing of at least two, and possibly three, source fluids. These source fluids were recognized as a sea water composition modified by high temperature water-rock reactions; meteoric recharge; and a hydrothermal fluid that had been equilibriated with high temperature reservoir rocks and magmatic volatiles. Although the major alkali and halide elements show clearly increasing trends with time, only a few of the trace transition metals show a similar trend. The rare earth elements were typically found at low concentrations and appeared to be highly variable with time. Studies of the precipitation characteristics of silica showed that amorphous silica deposition rates were highly sensitive to fluid pH and that increases in fluid pH above about 8.5 could flocculate more than 80 percent of the suspended colloidal silica in excess of its solubility. Addition of transition metal salts were also found to enhance the recovery fractions of silica from solution. The amorphous silica precipitate was also found to strongly scavenge the alkaline earth and transition metal ions naturally present in the brines; mild acid treatments were shown to be capable of removing substantial fractions of the scavenged metals from the silica flocs, yielding a moderately pure gelatinous by-product. Further work on the silica precipitation process is recommended to improve our ability to control silica scaling from high temperature geothermal fluids or to recover a marketable silica by-product from these fluids prior to reinjection.

West, H. B.; Delanoy, G. A.; Thomas, D. M.; Gerlach, D. C.; Chen, B.; Takahashi, P.; Thomas, D. M.

1992-03-01

114

Trace element and isotope geochemistry of geothermal fluids, East Rift Zone, Kilauea, Hawaii  

SciTech Connect

A research program has been undertaken in an effort to better characterize the composition and the precipitation characteristic of the geothermal fluids produced by the HGP-A geothermal well located on the Kilauea East Rift Zone on the Island of Hawaii. The results of these studies have shown that the chemical composition of the fluids changed over the production life of the well and that the fluids produced were the result of mixing of at least two, and possibly three, source fluids. These source fluids were recognized as: a sea water composition modified by high temperature water-rock reactions; meteoric recharge; and a hydrothermal fluid that had been equilibrated with high temperature reservoir rocks and magmatic volatiles. Although the major alkali and halide elements show clearly increasing trends with time, only a few of the trace transition metals show a similar trend. The rare earth elements, were typically found at low concentrations and appeared to be highly variable with time. Studies of the precipitation characteristics of silica showed that amorphous silica deposition rates were highly sensitive to fluid pH and that increases in fluid pH above about 8.5 could flocculate more than 80% of the suspended colloidal silica in excess of its solubility. Addition of transition metal salts were also found to enhance the recovery fractions of silica from solution. The amorphous silica precipitate was also found to strongly scavenge the alkaline earth and transition metal ions naturally present in the brines; mild acid treatments were shown to be capable of removing substantial fractions of the scavenged metals from the silica flocs yielding a moderately pure gelatinous by-product. Further work on the silica precipitation process is recommended to improve our ability to control silica scaling from high temperature geothermal fluids or to recover a marketable silica by-product from these fluids prior to reinjection.

West, H.B.; Delanoy, G.A.; Thomas, D.M. (Hawaii Univ., Honolulu, HI (United States). Hawaii Inst. of Geophysics); Gerlach, D.C. (Lawrence Livermore National Lab., CA (United States)); Chen, B.; Takahashi, P.; Thomas, D.M. (Hawaii Univ., Honolulu, HI (United States) Evans (Charles) and Associates, Redwood City, CA (United States))

1992-01-01

115

Vapor Pressure Isotope Effects and the Stable Isotope Geochemistry of the Martian Surface  

Microsoft Academic Search

The stable isotope geochemistry of light elements (H, C, N, O and S) is a tool in the search for evidence of life on bodies other than the earth for several reasons: the elements in question are used by all known or easily imagined life forms; several mass spectrometric and spectroscopic methods for measuring their isotopic compositions exist and are

J. M. Eiler

2002-01-01

116

Uncovering the Global Life Cycles of the Rare Earth Elements  

NASA Astrophysics Data System (ADS)

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

Du, Xiaoyue; Graedel, T. E.

2011-11-01

117

Uncovering the global life cycles of the rare earth elements.  

PubMed

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, critical technologies. Knowledge of the life cycles of REE remains sparse, despite the current heightened interest in their future availability. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supplies vulnerable to short and long-term disruption. To provide an improved perspective we derived the first quantitative life cycles (for the year 2007) for ten REE: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and yttrium (Y). Of these REE, Ce and Nd in-use stocks are highest; the in-use stocks of most REE show significant accumulation in modern society. Industrial scrap recycling occurs only from magnet manufacture. We believe there is no post-customer recycling of any of these elements. PMID:22355662

Du, Xiaoyue; Graedel, T E

2011-11-04

118

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

PubMed

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

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

2012-03-01

119

Rare earth element patterns in biotite, muscovite and tourmaline minerals  

SciTech Connect

Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10/sup -4/ g/g to 10/sup -10g//sub g/. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization.

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

1986-04-21

120

Major and Trace element Geochemistry of Hydrothermal Minerals From the Sudbury Structure: Implications for Fluid Architecture  

NASA Astrophysics Data System (ADS)

The Sudbury structure mainly comprises a layered intrusive body (the 2.5 km thick Sudbury Igneous Complex; SIC), and the overlying 1.4 km thick Onaping (OF) and Vermilion (VF) Formations. This sequence and the underlying basement have been affected by extensive hydrothermal fluid circulation, postulated to involve deep formational brines, sea water, and/or orthomagmatic fluids derived from the SIC. Late-stage magmatic fluids are indicated by miarolitic cavities (Kfs-Qtz-Ep-Chl-Hbl), which are common throughout the upper part of the SIC but also occur in the overlying Onaping Intrusion (OI) and towards the footwall of the SIC. Mineralogically similar veins (Ep-Qtz-Kfs-Chl) also occur in the SIC and OI, and possibly represent the migration of these orthomagmatic fluids away from their source. Hydrothermal epidote shows similar major element chemistry (e.g. Fe/Fe+Al) irrespective of epidote type or stratigraphic position. In general, epidote from the SIC displays average Fe/Fe+Al ratios from of 0.16 to 0.32. Similar values (0.19 to 0.32) are reported for epidote from the OF. Epidote from cavities are characterized by relatively flat HREE patterns, variable degrees of LREE fractionation, and moderate to strong positive Eu anomalies (Type I). However, some show a relatively flat LREE pattern, slightly enriched HREE and moderate positive Eu anomalies (Type II). A third group (Type III), show steep REE patterns with moderate to strong fractionation between HREE and LREE, and moderate positive Eu anomalies. Vein epidote is characterized by Type I patterns only. These data suggest that fluids of comparable temperature and composition precipitated epidote and related minerals in both miarolitic cavities and veins through the SIC and OF. Calcite occurs as a replacement mineral in the OF, in amygdules (Qtz-Chl-Cal-Ep-Sulph) in syn-depositional aphanitic dikes in the OF, and as bands, discordant aggregates and replacement phases (blocky calcite) in the VF, which lies above the OF. Amygdule calcite displays either relatively flat REE patterns, with minor LREE fractionation and no Eu anomalies (not observed in Ep), or the Type III patterns seen in epidote. Replacement carbonate in the OF show the Type I and II patterns characteristic of epidote. Banded and unmineralized blocky calcite displays flat, yet irregular, REE patterns, with minor negative Ce anomalies, and no Eu anomaly. Discordant and blocky calcite associated with minor sulphide mineralization displays moderate LREE fractionation and flat to slightly enriched HREE patterns, with a strong positive Y anomaly and negative Ce and Eu anomalies, suggesting seawater involvement. The REE geochemistry of VF carbonates is thus distinctly different from that of epidote and carbonate deeper in the system. Similar REE patterns observed in hydrothermal epidote and carbonates suggest that fluids of similar composition and temperature circulated through both the SIC and OF. However, the distinct character of some sulphide-related VF carbonates suggests the involvement of different fluids, or deposition under different conditions. The distinct positive Eu anomaly in epidote and carbonate is consistent with precipitation from relatively hot, reduced fluids. Variations in REE chemistry within single samples suggests that the REE systematics are complex and that fluids evolved with time. Finally, a potential fluid connection between the footwall and hanging wall of the SIC, as has been previously suggested, is potentially demonstrated by the ubiquitous Eu anomaly found across the entire Sudbury hydrothermal system.

Campos-Alvarez, N. O.; Samson, I. M.; Fryer, B. J.; Ames, D. E.

2007-12-01

121

Preparation of microcapsules containing rare-earth metal elements.  

PubMed

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

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

122

Variations in trace element geochemistry in the Seine River Basin based on floodplain deposits and bed sediments  

NASA Astrophysics Data System (ADS)

Between 1990 and 1995 a series of bed sediment, suspended sediment and fresh floodplain samples were collected within the Seine River Basin, in France, to evaluate variations in trace element geochemistry. Average background trace element levels for the basin were determined from the collection and subsequent analyses of bed sediment samples from small rural watersheds and from a prehistoric (5000 BP) site in Paris. Concentrations are relatively low, and similar to those observed for fine-grained bed sediments from unaffected areas in the United States and Canada. However, the concentrations are somewhat higher than the reference levels presently adopted by French water authorities for areas north of the Seine Basin, which have similar bedrock lithologies. Downstream trace element variations were monitored in 1994 and 1995 using fresh surficial floodplain samples that were collected either as dried deposits a few days after peak discharge, or immediately after peak discharge (under 30 cm of water). Chemical comparisons between fresh floodplain deposits, and actual suspended sediments collected during flood events, indicate that, with some caveats, the former can be used as surrogates for the latter. The floodplain sediment chemical data indicate that within the Seine Basin, from the relatively unaffected headwaters through heavily affected urban streams, trace element concentrations vary by as much as three orders of magnitude. These trace element changes appear to be the result of both increases in population as well as concomitant increases in industrial activity. (This article is a US government work and is in the public domain in the United States.)

Horowitz, Arthur J.; Meybeck, Michel; Idlafkih, Zayed; Biger, Erwan

1999-06-01

123

Variations in trace element geochemistry in the Seine River Basin based on floodplain deposits and bed sediments  

USGS Publications Warehouse

Between 1990 and 1995 a series of bed sediment, suspended sediment and fresh floodplain samples were collected within the Seine River Basin, in France, to evaluate variations in trace element geochemistry. Average background trace element levels for the basin were determined from the collection and subsequent analyses of bed sediment samples from small rural watersheds and from a prehistoric (5000 BP) site in Paris. Concentrations are relatively low, and similar to those observed for fine-grained bed sediments from unaffected areas in the United States and Canada. However, the concentrations are somewhat higher than the reference levels presently adopted by French water authorities for areas north of the Seine Basin, which have similar bedrock lithologies. Downstream trace element variations were monitored in 1994 and 1995 using fresh surficial floodplain samples that were collected either as dried deposits a few days after peak discharge, or immediately after peak discharge (under ??? 30 cm of water). Chemical comparisons between fresh floodplain deposits, and actual suspended sediments collected during flood events, indicate that, with some caveats, the former can be used as surrogates for the latter. The floodplain sediment chemical data indicate that within the Seine Basin, from the relatively unaffected headwaters through heavily affected urban streams, trace element concentrations vary by as much as three orders of magnitude. These trace element changes appear to be the result of both increases in population as well as concomitant increases in industrial activity. This article is a US government work and is in the public domain in the United States.

Horowitz, A. J.; Meybeck, M.; Idlafkih, Z.; Biger, E.

1999-01-01

124

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

National Technical Information Service (NTIS)

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

K. E. Mironov L. A. Chernikova

1970-01-01

125

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

National Technical Information Service (NTIS)

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

D. N. Trifonov

1970-01-01

126

The astysphere and urban geochemistry—a new approach to integrate urban systems into the geoscientific concept of spheres and a challenging concept of modern geochemistry supporting the sustainable development of planet earth  

Microsoft Academic Search

Background, aim, and scope  In 1875, the geoscientist Walter Suess introduced several spheres, such as the lithosphere and the atmosphere to promote a\\u000a comprehensive understanding of the system earth. Since then, this idea became the dominating concept for the understanding\\u000a of the distribution of chemical elements in the system earth. Meanwhile, due to the importance of human beings on global element

Stefan Norra

2009-01-01

127

EXAFS study of rare-earth element coordination in calcite  

NASA Astrophysics Data System (ADS)

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

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

2002-09-01

128

Trace Element Geochemistry of Matrix Glass from the Bedout Impact Structure,Canning Basin NW Australia  

NASA Astrophysics Data System (ADS)

We report on geochemical and petrographic analysis of separated matrix glass from Lagrange-1 and Bedout-1 drill cores that penetrated the Bedout structure offshore NW Australia. The results support the conclusion that the Bedout structure was produced by a a major ET impact at the end-Permian that generated shock melted glass and impact breccias (Becker et al., Science, v.304, p.1469, 2004) The Bedout structure is a 30 km, circular, 1.5 km uplifted basment high that occurs on the passive margin offshore NW Australia. The isolated feature, covered by 3 km of Triassic to Recent sediments,is not consistent with any typical volcanic province (i.e. arc or hotspot volcanism). This hypothesis is supported by the unique mineralogy and chemistry of the matrix glass. At Lagrange, major elements crudely resemble low-K, Fe-Ti basalts while the trace element patterns have two distinct signatures. The lower 250 m of Lagrange (3260 - 3010 m depth) have essentially flat REE and "spider" patterns that superficially resemble some E-MORB; a signal not typically found in arc, hotspot or continental margin settings. The upper 150 meters (3000 - 2850m) of Lagrange and the entire Bedout core (3030 - 3070m) have similar light REE-enriched patterns but low levels of alkalis, alkaline-earths and high field strength elements. Again, the chemistry is not consistent with an arc or hotspot setting, based on the low Ba and extremely low Sr (30-110 ppm) concentrations. Based on the geophysical, chemical and petrologic evidence, we hypothesize that the Bedout structure formed as the result` of an ET impact with Permian age rift margin basalts and continental sediment. The basalts did not completely melt as evidenced by the abundance of large (1 mm) An50 plagioclase,that exist as both crystalline plag and shock melted maskelynite. Plagioclase is the major repository of Sr in basalts and the lack of a plagioclase contribution to the melt glass is reflected in the low Sr abundance. Shock-transformed plagioclase glass that still retains the lath shape and chemistry of An50 are one of the major indicators of the impact origin for Bedout.

Poreda, R. J.; Basu, A. R.; Chakrabarti, R.; Becker, L.

2004-12-01

129

The Significance of Rare Earth Element Partition Coefficients in Zircon  

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

130

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

National Technical Information Service (NTIS)

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

J. E. Selle

1992-01-01

131

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

Microsoft Academic Search

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

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

1958-01-01

132

Revisiting the rare earth elements in foraminiferal tests [rapid communication  

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

133

Ternary phosphates of rubidium-cesium-rare earth element  

SciTech Connect

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

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

1986-06-01

134

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

Microsoft Academic Search

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

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

1971-01-01

135

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

PubMed

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

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

2012-08-01

136

Introduction to Geochemistry, Third Edition  

NASA Astrophysics Data System (ADS)

Krauskopf and Bird's third edition of Introduction to Geochemistry should remain a standard for introductory textbooks in this field into the 21st century. Anyone teaching an introductory course in geochemistry must consider using this text in class. I have used the book in my classes for the last 27 years; it always serves as the backbone of my courses, though I supplement its view of geochemistry with my own for balance. The third edition, like the earlier editions, is meant to introduce geochemistry to undergraduate students who have taken basic courses in Earth sciences, chemistry, and mathematics. It can also be used at the graduate level for Earth, ocean, and environmental science students with weak academic backgrounds in general geochemistry.

Mackenzie, Fred T.

137

Elemental Geochemistry of Samples From Fault Segments of the San Andreas Fault Observatory at Depth (SAFOD) Drill Hole  

NASA Astrophysics Data System (ADS)

Elemental geochemistry of mudrock samples from phase 2 drilling of the San Andreas Fault Observatory at Depth (SAFOD) is presented from bore hole depths of 3066 m to 3169 m and from 3292 m to 3368 m, which contain a creeping section and main trace of the fault, respectively. In addition to preparation and analysis of whole rock sample, fault grains with neomineralized, polished surfaces were hand picked from well-washed whole rock samples, minimizing the potential contamination from drilling mud and steel shavings. The separated fractions were washed in deionized water, powdered using a mortar and pestle, and analyzed using an Inductively Coupled Plasma- Optical Emission Spectrometer for major and minor elements. Based on oxide data results, systematic differences in element concentrations are observed between the whole rock and fault rock. Two groupings of data points are distinguishable in the regions containing the main trace of the fault, a shallow part (3292- 3316 m) and a deeper section (3320-3368 m). Applying the isocon method, assuming Zr and Ti to be immobile elements in these samples, indicates a volume loss of more than 30 percent in the shallow part and about 23 percent in the deep part of the main trace. These changes are minimum estimates of fault-related volume loss, because the whole rock from drilling samples contains variable amount of fault rock as well. Minimum estimates for volume loss in the creeping section of the fault are more than 50 percent when using the isocon method, comparing whole rock to plucked fault rock. The majority of the volume loss in the fault rocks is due to the dissolution and loss of silica, potassium, aluminum, sodium and calcium, whereas (based on oxide data) the mineralized surfaces of fractures appear to be enriched in Fe and Mg. The large amount of element mobility within these fault traces suggests extensive circulation of hydrous fluids along fractures that was responsible for progressive dissolution and leaching of the wall rock during faulting.

Tourscher, S. N.; Schleicher, A. M.; van der Pluijm, B. A.; Warr, L. N.

2006-12-01

138

Rare earth element fractionation in magmatic Ca-rich garnets  

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

139

Rare earth element analysis indicates micropollutants in an urban estuary  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

140

Rare earth elements as a fingerprint of soil components solubilization  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

141

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

Microsoft Academic Search

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

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

1977-01-01

142

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

Microsoft Academic Search

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

Kevin H Johannesson; Xiaoping Zhou

1999-01-01

143

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

Microsoft Academic Search

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

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

1977-01-01

144

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

Microsoft Academic Search

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

Peng

1973-01-01

145

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

National Technical Information Service (NTIS)

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

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

1995-01-01

146

Trace element cycling in a subterranean estuary: Part 1. Geochemistry of the permeable sediments  

Microsoft Academic Search

Subterranean estuaries are characterized by the mixing of terrestrially derived groundwater and seawater in a coastal aquifer. Subterranean estuaries, like their river water-seawater counterparts on the surface of the earth, represent a major, but less visible, hydrological and geochemical interface between the continents and the ocean. This article is the first in a two-part series on the biogeochemistry of the

Matthew A. Charette; Edward R. Sholkovitz; Colleen M. Hansel

2005-01-01

147

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

Microsoft Academic Search

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

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

1978-01-01

148

Trace element geochemistry of brackish-water coals in the central Alberta Plains, Canada  

SciTech Connect

Concentrations of the elements As, B, Br, Cl, Cr, Co, Mn, Mo, Na, Sb, Se, Th, U, V, and Zn were determined in ply-by-ply samples from two sections of subbituminous coal from seam 3, Vesta Mine, Alberta Plains. Mean concentrations of these elements are low when compared to western Canadian coals of similar rank, or to world coals. Elements were differentiated on the basis of their inorganic association, organic association, or intermediate (mixed) association. Results are presented.

Gentzis, T. [Alberta Research Council, Edmonton, Alberta (Canada); Goodarzi, F. [Geological Survey of Canada, Calgary, Alberta (Canada). Inst. of Sedimentary and Petroleum Geology

1997-06-01

149

Light elements in the Earth's core: Fe3X compounds  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

150

Trace element geochemistry in the waters of Pulicat lake, South India  

Microsoft Academic Search

The distribution of trace elements like Cu, Zn, Ni, Co and Mn in the waters of Pulicat lake has been studied in four aqueous environments — northern, central, southern and channel parts. It is observed that the concentration of the trace elements increase with increase of pH, chlorides and sodium in both monsoon and dry seasons. The concentration and the

M. Nagaraju; K. L. Narasimharao; H. Gossmann; B. Lacaze

1994-01-01

151

Heavy metals, trace elements and sediment geochemistry at four Mediterranean fish farms.  

PubMed

Trace element concentrations in sediment were investigated at four fish farms in the Eastern Mediterranean Sea. Fish farms effects were negligible beyond 25-50 m from the edge of the cages. Based on elemental distribution, sediments from the farms were separated into coarse oxidized and silty reduced ones. Fish feed is richer in P, Zn and Cd than reference and impacted stations. Comparison among impacted stations and the respective reference stations shows that, in anoxic sediments, all elements had higher concentrations at the impacted stations than at reference stations while in oxic sediments, many elemental concentrations were lower at impacted stations than at reference stations. The behavior of elements and therefore their distribution is affected by changes in sediment grain size, organic content and redox regime. Elements in sediments around fish farms can be clustered into five groups according to these environmental variables. In silty and anoxic sediments, element concentrations were higher than in coarse and oxic ones. Several approaches were used to assess potential sediment toxicity (enrichment factors, geoaccumulation indices, contamination factors) as well as to assess the potential danger to aquatic life (Sediment Quality Guidelines, SQG). Cu, Zn and Fe can cause from threshold to extreme effects on aquatic life in anoxic, fine-grained sediments and As can cause threshold effects in all types of sediment around fish farms. Other elements (Cr, Pb, Mn) can also cause unwanted effects when compounded with elevated background levels. PMID:23268141

Kalantzi, I; Shimmield, T M; Pergantis, S A; Papageorgiou, N; Black, K D; Karakassis, I

2012-12-23

152

Geochemistry of trace elements in the highland lunar rocks based on SRXFA data  

NASA Astrophysics Data System (ADS)

X-ray fluorescence analysis using synchrotron radiation (SRXFA) has been applied for determination of trace elements in the highland lunar rocks (Luna 20 and Apollo 16). On the basis of the distribution of Rb, Sr, Y, Zr, and Nb in 69 lunar highland fragments six geochemical groups of rocks with various aluminium and trace element contents were distinguished for each station. They have various levels of trace element content. This suggests the various petrological processes: cumulation of rock-forming minerals and partial melting of source rocks. The last process lead up to enriching in trace elements in rocks formed from these melts. The distribution of trace elements in highland and mare rocks of the Moon were compared.

Tarasov, L. S.; Kudryashova, A. F.; Ulyanov, A. A.; Baryshev, V. B.; Zolotarev, K. V.

1998-02-01

153

RECONSTRUCTING LAURENTIDE ICE SHEET MELTWATER GEOCHEMISTRY USING COMBINED STABLE ISOTOPE AND LASER ABLATION TRACE ELEMENT ANALYSES  

NASA Astrophysics Data System (ADS)

Little is known about the oxygen isotope evolution of Northern hemisphere ice sheets during past glacial cycles, with the exception of results from models and calculations based on whole ocean ?18O change. Reconstructing changes in the ?18Owater of the global ocean assumes a homogeneous ?18O value for contributions from Northern hemisphere ice sheets with a mass balance contribution from the Southern hemisphere. Because oceanic ?18Ow forms a crucial baseline for deconvolving the combined signal of temperature and hydrologic changes recorded in foraminiferal calcite, constraints on the contributions of melting ice sheets form a fundamental component of reconstructions of global ocean ?18Ow changes on glacial timescales. Here we present a novel geochemical technique to compute the oxygen isotopic composition of Laurentide Ice Sheet (LIS) meltwater flowing into the Gulf of Mexico during periods of rapid ice sheet melting. The technique combines data from different types of geochemical analyses on individual shells of the planktonic foraminifera Orbulina universa to compute meltwater geochemistry, using laser ablation ICP-MS to measure Mg/Ca (a temperature proxy) and Ba/Ca (a salinity proxy) and isotope ratio mass spectrometry to measure ?18O (a temperature and ?18Owater proxy) on remaining shell material. O. universa has a very large temperature and salinity tolerance (9-30°C; 23-45 psu) and broad depth habitat (0-80 m), so an assemblage of individual shells from a single core interval records a range of water conditions. We have selected deglacial meltwater intervals from core MD02-2550 (26.95°N, 91.35°W, 2245 m water depth), collected from the anoxic Orca Basin in the Gulf of Mexico, for a proof of concept demonstration. From each interval, we combine measurements of Mg/Ca, Ba/Ca, and ?18O on 30-100 individual O. universa. The ?18O from each shell reflects the combined influence of temperature and ?18Owater, where this latter value is a function of mixing between seawater and ice sheet meltwater runoff. Mg/Ca data provide an independent reconstruction of temperature, and Ba/Ca is used as a proxy for salinity in the vicinity of riverine outflow. Combining these data permits us to compute both salinity and ?18Owater for each discrete foraminifera shell. We demonstrate that when an assemblage of salinity and ?18Owater paired data are combined, we are able to compute the ?18Owater of the freshwater (glacial) endmember.

Vetter, L.; Spero, H. J.; Eggins, S. M.; Flower, B. P.; Williams, C. C.

2009-12-01

154

Trace Element Geochemistry of a Lunar Granulite: Evidence from Northwest Africa 3163  

NASA Astrophysics Data System (ADS)

Northwest Africa (NWA) 3163 is a granulitic breccia most likely from the lunar farside. NWA has among the lowest incompatible-trace-element concentrations of any known lunar sample and may be a fragment of nearly pristine lower crust.

Shafer, J. T.; Brandon, A. D.; Lapen, T. J.; Peslier, A. H.; Irving, A. J.

2011-03-01

155

Geochemistry and the Environment. Volume I. The Relation of Selected Trace Elements to Health and Disease.  

National Technical Information Service (NTIS)

Possible relationships between the geographic distribution of certain elements and patterns of disease are considered in this report which consists of papers from a workshop on the Geochemical Environment in Relation to Health and Disease. Common methods ...

1974-01-01

156

Petrology and trace element geochemistry of the Honolulu volcanics, Oahu: implications for the oceanic mantle below Hawaii.  

USGS Publications Warehouse

These volcanic rocks are the products of small-volume, late-stage vents along rifts cutting the older massive Koolan tholeiitic shield on Oahu. Most of the lavas and tuffs have the geochemical features expected of near-primary magmas derived from a peridotite source with olivine Fo87-89, e.g. 100 Mg/(Mg + Fe2+) > 65, Ni > 250 p.p.m. and the presence of ultramafic mantle xenoliths at 18 of the 37 vents. Thus the geochemistry of the alkali olivine basalt, basanite, nephelinite and nepheline melilitite lavas and tuffs of these Honolulu volcanic rocks has been used to deduce the composition of their mantle source and the conditions under which they were generated by partial melting in the mantle. New major- and trace-element analyses for 31 samples are tabulated and indicate derivation by partial melting of a garnet (<10%) lherzolite source which was isotopically homogeneous and compositionally uniform for most major and trace elements, though apparently heterogeneous in TiO2, Zr, Hf, Nb and Ta (due perhaps to the low inferred degrees of melting which failed to exhaust the source in minor residual phases). In comparison with estimates of a primordial mantle composition and the mantle source of MORB, the garnet peridotite source of these Honolulu volcanics was increasingly enriched in the sequence heavy REE, Y, Tb, Ti, Sm, Zr and Hf, for which a multi-stage history is required. This composition differs from the source of the previously erupted tholeiitic shield, nor is it represented in the upper-mantle xenoliths in the lavas and tuff of the unit.-R.A.H.

Clague, D. A.; Frey, F. A.

1982-01-01

157

Minor element geochemistry of groundwater from an area with prevailing saline groundwater in Chikhwawa, lower Shire valley (Malawi)  

NASA Astrophysics Data System (ADS)

Groundwater resources with high salinity content are found in some parts of the lower Shire River valley (Malawi). This paper discusses the geochemistry of minor elements with regards to the prevailing salinity. Hierarchical clustering and principal component analyses were used to identify factors which relate to both minor elements and samples and were interpreted as reflecting the influence of prevailing saline/brackish groundwater. Concentrations of lead (Pb), boron (B), strontium (Sr) and chromium (Cr) were associated with groundwater with high content of total dissolved solids (TDS). Speciation calculations indicated that dissolved Sr, barium (Ba) and lithium (Li) were mainly in the form of free aqueous ions whereas hydrolysed species were significant for aluminium (Al) and Cr, and carbonate complexes for Pb. Chloride complexes were prevalent for silver (Ag). Solubility of cerussite (PbCO3) and barite (BaSO4) was shown to act as a control on the levels of Pb and Ba, respectively. Thus, Ba concentrations were very low in saline groundwater owing to their high sulphate content. A relatively variable B concentration in the groundwater samples was explained using a binary mixing model of saline and fresh groundwater. The mixing of fresh groundwater with saline groundwater was concomitant with high Na+/Ca2+ ratios and enrichment of B, probably by desorption from clays. The WHO drinking water guidelines for Ba, B, Cr and Pb were exceeded in 6.5%, 9.7%, 16.1% and 64.5% of all the samples, respectively. However, all samples were below the Malawian specification of B in borehole and shallow well water quality (MS 733:2005) of 5.0 mg/L.

Monjerezi, Maurice; Vogt, Rolf D.; Gebru, Asfaw Gebretsadik; Saka, John D. K.; Aagaard, Per

158

Major element, REE, and Pb, Nd and Sr isotopic geochemistry of Cenozoic volcanic rocks of eastern China: implications for their origin from suboceanic-type mantle reservoirs  

USGS Publications Warehouse

Major- and rare-earth-element (REE) concentrations and UThPb, SmNd, and RbSr isotope systematics are reported for Cenozoic volcanic rocks from northeastern and eastern China. These volcanic rocks, characteristically lacking the calc-alkaline suite of orogenic belts, were emplaced in a rift system which formed in response to the subduction of the western Pacific plate beneath the eastern Asiatic continental margin. The rocks sampled range from basanite and alkali olivine basalt, through olivine tholeiite and quartz tholeiite, to potassic basalts, alkali trachytes, pantellerite, and limburgite. These rock suites represent the volcanic centers of Datong, Hanobar, Kuandian, Changbaishan and Wudalianchi in northeastern China, and Mingxi in the Fujian Province of eastern China. The major-element and REE geochemistry is characteristic of each volcanic suite broadly evolving through cogenetic magmatic processes. Some of the outstanding features of the isotopic correlation arrays are as follows: (1) NdSr shows an anticorrelation within the field of ocean island basalts, extending from the MORB end-member to an enriched, time-averaged high Rb Sr and Nd Sr end-member (EM1), (2) SrPb also shows an anticorrelation, similar to that of Hawaiian and walvis Ridge basalts, (3) NdPb shows a positive correlation, and (4) the 207Pb 204Pb vs 206Pb 204Pb plot shows linear arrays parallel to the general trend (NHRL) for MORB on both sides of the geochron, although in the 208Pb 204Pb vs 206Pb 204Pb plot the linear array is significantly displaced above the NHRL in a pattern similar to that of the oceanic island basalts that show the Dupal signatures. In all isotope correlation patterns, the data arrays define two different mantle components-a MORB-like component and an enriched mantle component. The isotopic data presented here clearly demonstrate the existence of Dupal compositions in the sources of the continental volcanic rocks of eastern China. We suggest that the subcontinental mantle beneath eastern China served as the reservoir for the EMI component, and that the MORB component was either introduced by subduction of the Kula-Pacific Ridge beneath the Asiatic plate in the Late Cretaceous, as proposed by Uyeda and Miyashiro, or by upwellings in the subcontinental asthenosphere due to subduction. ?? 1991.

Basu, A. R.; Wang, Junwen; Huang, Wankang; Xie, Guanghong; Tatsumoto, M.

1991-01-01

159

Attenuation of rare earth elements in a boreal estuary  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

160

Nanomaterials made of earth-abundant elements for photovoltaics  

NASA Astrophysics Data System (ADS)

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

Molk, Doreen

161

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

USGS Publications Warehouse

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

Birdwell, Justin E.

2012-01-01

162

Miocene Coral Skeleton Rare Earth Element Patterns Reflect River Discharge  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

163

Processes controlling trace element geochemistry of Arabian Sea sediments during the last 25,000 years  

Microsoft Academic Search

Thirty seven deep-sea sediment cores from the Arabian Sea were studied geochemically (49 major and trace elements) 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

Frank Sirocko; Dieter Garbe-Schönberg; Colin Devey

2000-01-01

164

Metabasalts from the Troodos Massif, Cyprus: Genetic implication deduced from petrography and trace element geochemistry  

Microsoft Academic Search

A wide variety of data support the contention that the Troodos massif, Cyprus is a fragment of oceanic lithosphere formed at a constructive margin some 85 m.y. ago. However, Troodos rocks differ significantly in major and trace element content and mineral parageneses from those formed at present day active constructive margins. It is here argued that the geochemical and petrographic

John D. Smewing; Kapo O. Simonian; Ian G. Gass

1975-01-01

165

Geochemistry of rare and minor elements in sediments from Brazil Basin of Atlantic Ocean  

Microsoft Academic Search

This paper reviews the features of the rare and minor elements in the sediment samples recovered from the Brazil Basin at the location of the Station No. 1537 in the Atlantic Ocean during the 18th cruise of the Research Vessel \\

Irina Vvedenskaya; Alexander Dubinin

2010-01-01

166

Trace Element Geochemistry of Metapelitic Rocks of the Medio Rio Doce, Minas Gerais Region.  

National Technical Information Service (NTIS)

Representative samples of schists and gneisses, which was metamorphosed in the sillimanite isograde, have been submited to spectrographic analyses for trace-elements. The concentrations and standard deviation (in ppm) are: Be:6,25 (3,6); Sc:29 (12); Ti:57...

J. H. G. Sad

1983-01-01

167

The geochemistry of river particulates from the continental USA: major elements.  

PubMed

River particulates have been collected from twenty-three rivers from throughout the continental USA. The rivers drain mostly large basins (basin areas range from 2.1 x 10(3) to 2970 x 10(3) km2) composed of mixed lithologies, and spanning a wide range of climatic conditions as evidenced by a large variation in air and ground water temperatures, precipitation, and runoff. Suspended particulates have been analyzed for organic and inorganic carbon, as well as the major elements Al, Fe, Mn, K, Si, Ca, Mg, and Na. Also determined were suspended sediment loads at the time of sampling, particle surface areas, and grain size distributions. Five-year average river water chemistry and suspended sediment concentrations, obtained from USGS water supply reports, are also included as supporting information. Particle chemistry systematically varies with rates of runoff, with high runoff rivers transporting the most heavily altered particulates and low runoff rivers carrying the least altered. Degrees of alteration are indicated by the extent to which the refractory, nonmobile elements Al and Fe are concentrated into the particulates and the extent to which the most easily weathered elements Na, Ca, and Mg have been leached. Overall, the susceptibility of elements towards leaching is consistent with numerous previous descriptions of element mobility on weathering. A simple predictive model has been developed to explore and explain the observed trends between particle composition and river runoff. Thus, the elemental composition of riverine particulates may be given by the expression PCOi = [(Propi)TM-DCOi]/SS, where PCOi is the concentration of element i (as the oxide) in a riverine particulate, Propi is the proportion of i (as the oxide) in unweathered rock, DCOi is the dissolved concentration of i (as the equivalent oxide), TM is the total rock derived mass dissolved in river water, and SS is suspended sediment concentration. To utilize this equation, a model was first developed to predict the concentration of river solutes with the input of temperature, precipitation, and a limited number of weathering parameters. Combining this solute model with the above predictive equation for particle composition, it was discovered that the observed trends between particle composition and runoff require the special circumstance of decreasing SS with increasing runoff. Hence, the composition of river particulates depends both on the climate parameters of runoff and temperature (as they control dissolved river chemistry) and the nonclimate parameters including elevation, relief, tectonics, and basin area that control the SS load of rivers. PMID:11540476

Canfield, D E

1997-08-01

168

Major Element Geochemistry of Biofilms in a Silica-Precipitating Hot Spring  

NASA Astrophysics Data System (ADS)

Hydrothermal biofilm communities represent one of the best present-day representations of early microbial communities, dating back to 2.5 Ga, and possibly 3.8 Ga in the geologic record. Silica-precipitating hydrothermal springs have been thought to have great potential for biosignature preservation. The interactions of hydrothermal water, biofilms, and precipitated siliceous sinter, however, remain poorly constrained. To this end, we collected water and biofilm, as well as contextual sinter and rock samples from various hot springs in Yellowstone National Park. Here we focus on one hot spring in Sentinel Meadow (Lower Geyser Basin), with temperature and pH that vary from the source (93 C, pH 7.4) to the farthest of five collection points down channel (56 C, pH 8.2). Elemental analysis reveals that the biofilms are made up of from <1 to ~11 % dry wt. carbon and ~0.1 to 1% dry wt. nitrogen. Major element analysis via electron microprobe and complimentary x-ray fluorescence show that (excluding C and N from the total) SiO2 constitutes 86 to 94 % dry weight mass, with the rest made up of Al2O3 (3 to 8%), Na2O (1.7 to 3.7%), K2O (0.6 to 1.5%), and minor amounts of FeO, CaO, MgO, and TiO2 (<1%). Local sinter is SiO2 (97.5% dry wt.), Na2O (1.5%), and <1% Al2O3, FeO, K2O, CaO, MgO, and TiO2. In addition, sinter contains measurable amounts of carbon (1.4%) and nitrogen (0.2%). Discrepancies between the biofilm and sinter values show that the geochemical compositions of biofilms are not captured by the precipitating silica. If biofilms accumulated elements strictly from the water, then it would take as much as 440 L of water to supply 1 gram (dry wt) of biofilm with the elements contained therein, assuming complete uptake. This seems especially unlikely in the case of Al, which is quite dilute (~500 ppb), poses very little benefit nutritionally, and increases in concentration down channel. Other major element components also exhibit at least one, if not all, of these traits. A potential source of the elements found in biofilms is aeolian-deposited dust. Area country rock is dominated by siliceous volcanism, represented locally by rhyolite samples collected from Sentinel Meadow. With an average value of ~10 wt % Al2O3 for the surrounding country rock, it would take approximately 0.6 grams of the ground up rock as dust to account for the Al found in one gram of biofilm. The low Al2O3 content of the sinter indicates that the Al is not entombed from the biofilms. A hypothesis for the above discrepancies in Al (as well as other elements) is that dust deposited in the water is captured on the biofilm surfaces, and the biofilm community then breaks down the dust, utilizing any nutritionally or metabolically important elements, and either precipitating (for Si) or releasing (for Al) unnecessary elements.

Havig, J. R.; Shock, E. L.; Moore, G.

2007-12-01

169

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

Microsoft Academic Search

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

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

1970-01-01

170

Significance of zircon trace element geochemistry, the Shihu gold deposit, western Hebei Province, North China  

Microsoft Academic Search

The Shihu gold deposit is characterized by gold-bearing quartz-polymetallic sulfides and quartz veins. Both Mapeng granitoids batholith and intermediate-basic dikes intruded the metamorphic basement rocks, and are spatially associated with gold mineralization. Trace element abundances in zircons from the Shihu gold deposit, determined by laser-ablation microprobe ICPMS analysis, are sensitive to source rock type and crystallization environment. Concentrations of 21

Ye CAO; Shengrong LI; Huafeng ZHANG; Xiaobin LIU; Zhenzhen LI; Chong AO; Meijuan YAO

2011-01-01

171

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

Microsoft Academic Search

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

M. M. Weiner

1990-01-01

172

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

National Technical Information Service (NTIS)

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

A. V. Dolitskii

1968-01-01

173

Trace-element geochemistry of gradient hole cuttings: Beowawe geothermal area, Nevada  

SciTech Connect

Multielement geochemical analysis of drill cuttings from 26 shallow temperature-gradient drill holes and of surface rock samples reveals trace element 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 elements 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 element 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.

Christensen, O.D.

1980-12-01

174

Potassium and other minor elements in Porites corals: implications for skeletal geochemistry and paleoenvironmental reconstruction  

NASA Astrophysics Data System (ADS)

We investigated how the K/Ca, Na/Ca, Mg/Ca, and Sr/Ca ratios of powders ground from Porites coral skeletons are changed by cumulative chemical treatments to the powders: first with distilled/deionized water (DDW), next with 30 % H2O2 and then with 0.004 mol l-1 HNO3. The K/Ca, Na/Ca, and Mg/Ca ratios were decreased with the DDW treatment and then increased with the H2O2 and HNO3 treatments; the Sr/Ca ratio was slightly decreased through the cumulative treatments, suggesting fine-scale (tens of ?m or less) elemental heterogeneities in the skeleton—K, Na, and Mg are significantly enriched at the skeletal surface and also at the center of calcification (COC); in contrast, the heterogeneity of Sr is very small. We suggest that the principal mechanisms of K incorporation into coral skeleton are (1) ion incorporation into lattice defects/distortions and (2) ion adsorption onto crystal discontinuities (including crystal-organic matter interfaces) as forms of K+ and KSO4 -. Furthermore, we measured the element/Ca ratios of a modern Porites coral skeleton along its growth direction at 2-mm intervals. Results showed that all the element/Ca ratios displayed annual cycles, that the K/Ca and Na/Ca ratios covaried with each other, and that the annual-minimum K/Ca and Na/Ca ratios coincided with the annual high-density band in the skeleton. It is unclear what environmental factors may cause the covarying annual cycles of the K/Ca and Na/Ca ratios; however, as a possible explanation, the cycles may be due not to environmental factors, but to a combined effect of (1) the K and Na enrichment at the COC, (2) annual bands of high- and low-density skeleton, and (3) mm-scale element/Ca measurements along the skeletal growth direction. This kind of effect on geochemical proxies of which the concentrations significantly differ between the COC and surrounding skeleton may generate false or distorted paleoenvironmental signals.

Mitsuguchi, T.; Kawakami, T.

2012-09-01

175

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

Microsoft Academic Search

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

Xu Yue; Geng Jiping; Liu Yufeng

2006-01-01

176

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

Microsoft Academic Search

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

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

2003-01-01

177

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

NASA Astrophysics Data System (ADS)

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

Hassan, Mahmoud; Matuchova, Marie; Zdansky, Karel

2006-01-01

178

Trace element geochemistry of Jurassic coals from Eastern Black Sea Region, NE-Turkey  

SciTech Connect

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 element contents. The vertical distribution of trace elements 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.

Cebi, F.H.; Korkmaz, S.; Akcay, M. [Karadeniz Technical University, Trabzon (Turkey). Dept. of Geological Engineering

2009-07-01

179

Geochemistry of CI chondrites: Major and trace elements, and Cu and Zn Isotopes  

NASA Astrophysics Data System (ADS)

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 elements and U. After removal of one outlier sample, the spread of the results is considerably reduced. For most of the 46 elements 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).

Barrat, J. A.; Zanda, B.; Moynier, F.; Bollinger, C.; Liorzou, C.; Bayon, G.

2012-04-01

180

Magnetism of silicon doped with alkaline earth elements  

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

181

Petrology, major and trace element geochemistry, geochronology, and isotopic composition of granitic intrusions from the vicinity of the Bosumtwi impact crater, Ghana  

NASA Astrophysics Data System (ADS)

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 element geochemistry, 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.

Losiak, Anna; Schulz, Toni; Buchwaldt, Robert; Koeberl, Christian

2013-09-01

182

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

Microsoft Academic Search

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

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

1995-01-01

183

Siderophile and Chalcophile Element Geochemistry of Kerguelen Basic and Ultrabasic Xenoliths  

NASA Astrophysics Data System (ADS)

Seven basic and ultrabasic xenoliths from the Kerguelen Archipelago (KA), previously characterized for Sr, Nd, Pb isotopic and lithophile trace elements have been analyzed for the chalcophile and siderophile elements (incl. Os, Ir, Ru and Pt). The xenoliths include one dunite, two websterites, one lherzolite and three metagabbros. Previous work has shown that the dunite (91-114) has distinctive isotopic and geochemical features, reflecting incorporation of isolated fragments of continental lithosphere in the Kerguelen plume source. Although depleted in magmaphile elements such as Al2O3 and CaO and enriched in MgO and FeO, it is more fertile than depleted peridotites derived from cratonic lithopshere. Its high Ru/Pt (3.88) and low Pt/Ir (0.64) whole rock ratios however overlap those of cratonic (depleted) peridotites from the Kaapvaal Craton, and are similar to ratios found in residual sulfides enclosed in silicates from refractory cratonic peridotites high degree partial melting. Its anomalous Os/Ir ratio of 4.52 may be related to metasomatic modification. However, it is comparatively LREE depleted (both whole rock, or in clinopyroxene). This suggests that metasomatic modification was not related to LREE-Pt-enriched basaltic (or carbonatitic) melts. The bulk of the remaining ultrabasic (lherzolites, websterites) and basic (metagabbros) xenoliths represent tholeiitic cumulates or basaltic segregates which contributed to lithospheric growth beneath the KA via magmatic underplating mainly in the granulite facies. Iridium contents in metagabbros range from 0.46 to 1.47 ppb, whereas Pt ranges from 0.11-5.95 ppb. Only one metagabbro has chondritic PGE ratios (Os/Ir, Pt/Ir, Ru/Ir, ARC 835) and PGE contents <1 ppb. The remainder display a large range of Pt/Ir ratios from 0.24 to 9.25 resulting from varying Pt concentrations at relatively constant Ir contents. The average Ru/Ir ratio for all these xenoliths (including dunite 91-114) is suprachondritic and relatively constant at 2.36 ± 0.36 (1sd). This suggests that Ru and Ir are hosted in the same mineral phase and that these two elements are more compatible during mantle melting and segregation. The mantle source beneath Kerguelen appears to be enriched in Ru relative to Ir, a feature observed in other samples of abyssal peridotites, basalt-borne xenoliths and orogenic peridotites. The basic and ultrabasic xenoliths form a continuous trend in Ru/Pt vs. Pt/Ir space from highly suprachondritic Ru/Pt and subchondritic Pt/Ir to highly subchondritic Ru/Pt and suprachondritic Pt/Ir. Similar PGE are found in sulfides from depleted and fertile mantle samples, respectively. This trend in the metagabbros is interpreted to reflect increasing degrees of tholeiitic/basaltic magma at depth during silicate mineral fractionation/sulfide segregation. The positive correlation between Ru content and wt% MgO for all the xenoliths (including 91-114), suggests that olivine fractionation may play a role in the distribution of Ru.. Ultrabasic and basic xenoliths have Os/Ir ratios close to chondritic (0.82-1.22), except for one lherzolite (0.46, MG91-33) and websterite (2.43, GM92-252). Extensive re-equilibration and possibly melt infiltration at depth may have contributed to fractionation of Os from Ir. The combined chalcophile, siderophile and isotopic trends displayed by the xenoliths in this study argue for a combination of mixing and fractionation accompanying melting of different sources prior to magmatic underplating beneath the KA.

Pretorius, W.; Scoates, J.; Weis, D.; Mattielli, N.

2004-05-01

184

Characterization of the Sukinda and Nausahi ultramafic complexes, Orissa, India by platinum-group element geochemistry  

USGS Publications Warehouse

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 elements (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.

Page, N. J.; Banerji, P. K.; Haffty, J.

1985-01-01

185

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

PubMed

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

Kobayashi, Kohjiro; Nagao, Tatsuya; Ito, Masahisa

2012-07-26

186

Comparative geochemistry of basalts from the moon, earth, HED asteroid, and Mars: implications for the origin of the moon  

Microsoft Academic Search

Most hypotheses for the origin of the Moon (rotational fission, co-accretion, and collisional ejection from the Earth, including “giant impact”) call for the formation of the Moon in a geocentric environment. However, key geochemical data for basaltic rocks from the Moon, Earth, the howardite-eucrite-diogenite (HED) meteorite parent body (probably asteroid 4-Vesta), and the shergottite-nakhlite-chassignite (SNC) meteorite parent body (likely Mars),

Alex Ruzicka; Gregory A Snyder; Lawrence A Taylor

2001-01-01

187

Isotopic and trace element geochemistry of alkalic-mafic-ultramafic-carbonatitic complexes and flood basalts in NE India: Origin in a heterogeneous Kerguelen plume  

NASA Astrophysics Data System (ADS)

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 element 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 earth element (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 element 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 element geochemistry 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.

Ghatak, Arundhuti; Basu, Asish R.

2013-08-01

188

The elemental, ?44Ca, and ?26Mg geochemistry of granite weathering at pH = 1 and T = 25°C  

NASA Astrophysics Data System (ADS)

We conducted a plug flow reactor experiment at pH = 1 and T = 25°C using the 45-850 ?m size fraction of crushed Boulder Creek Granodiorite. The goal of the study was to improve understanding of granite weathering and constrain its influence on the Ca and Mg isotope geochemistry of terrestrial waters. Ultrapure, 0.1 N HCl was introduced at a flow rate of 0.051 mL min-1. Eluates were collected every 4 hrs for the first 24 hrs and every 24 hrs thereafter for a total of 3200 hrs at the time of writing. Elemental concentrations were measured by ICP-OES in solutions, mineral separates, and the bulk rock. Thin sections of the bulk rock were analyzed by electron microprobe to obtain additional information about mineral chemistry and modal abundances. When plotted versus time, concentrations of Al, Fe, K, Mg, and Si in the eluate display a rapid decrease followed by a rise, a brief steady-state, and finally, either a decay to zero or a new, lower steady-state. In contrast, concentrations of Ca, Na, and Sr display a rapid decrease followed by a nearly linear rise with time. All solutions are undersaturated with respect to secondary phases. We attribute the initial concentration decrease to the rapid dissolution of trace calcite and to leaching of freshly cleaved silicate mineral surfaces. Because biotite is the only Mg-bearing phase present in sufficient abundance to explain the total amount of Mg released after 3200 hrs, we infer the profiles for Al, Fe, K, Mg, and Si to mostly reflect biotite dissolution. Similarly, we infer the profiles for Ca, Na, and Sr to reflect plagioclase dissolution. The profiles are described using coupled conservation equations for the solid and fluid solved at non-steady-state using a 4th order Runge-Kutta numerical optimization scheme to minimize the residual sum of squares between measured and modeled data. The equations yield BET surface area normalized dissolution rates in good agreement with previous studies but also reveal the product of surface area and dissolution rate must increase with time. We find that mineral surface area increases as a power-law function of time through the roughness factor, ?. Dissolution therefore appears to increase available surface area, which in turn, increases dissolution. Hence, the elemental profiles reflect feedbacks between mineral abundance, dissolution rate, and available surface area. Over the timescale of the experiment, low abundance minerals with fast dissolution rates achieve high available surface areas and maximum elemental release rates after which continued dissolution decreases abundances and surface areas such that elemental release rates decline. The model predicts a similar effect for plagioclase but with concentrations rising over a longer timescale due to plagioclase’s greater abundance and slower dissolution rate. ?44Ca and ?26Mg measurements are underway by MC-TIMS and MC-ICP-MS, respectively. We will use the elemental chemistry model to constrain the behavior of Ca and Mg isotopes, quantify potential isotopic fractionation, and document other changes that may occur with time.

Ryu, J.; Jacobson, A. D.; Holmden, C.; Lundstrom, C.; Zhang, Z.

2009-12-01

189

Identification And Interpretation Of Eclogite Protoliths Using Immobile Element Geochemistry: Some New Methodologies  

NASA Astrophysics Data System (ADS)

Methodologies for fingerprinting metabasalts have been applied to eclogites with mixed success. Some, including Alpine examples famously studied by Gary Ernst >30 years ago, have been successfully assigned to tectonic settings and the results used to understand the now-disappeared ocean and its margins. Others, however, present two particular, well-documented problems: 1) many are cumulates rather than lavas and so have very low abundances of some elements as well as non-liquid compositions; 2) the subduction and exhumation processes can lead to infiltration of the protolith by subduction- and crustally-derived fluids/melts before and after eclogite-facies metamorphism and so impart apparent subduction or continental character even when none existed. Here we demonstrate new methodologies for dealing with these issues, taking as an example the eclogites from the Chinese Continental Scientific Drilling (CCSD) Deep Borehole. We adopt a set of immobile element proxies that highlight the presence and behaviour of particular cumulate phases (e.g. Cr for chromite, Ni for olivine, Sc,V for clinopyroxene, Ti,V for oxide, Ga for plagioclase, P and Zr for apatite and zircon, Nb for interstitial melt). Using a training data set from well-studied cumulate sequences such as Bushveld and Skaergaard, we can assign protolith rock names on the basis of these proxy elements. Variation diagrams enable us identify the crystallization sequence of the plutonic protolith, itself a function of the original tectonic setting. For example, the Borehole contains a thick, eclogite-facies cumulate sequence which we can reconstruct in detail as a layered complex containing cumulate dunite and peridotite, mela-troctolite, troctolite, gabbro, ferrogabbro, ferrodiorite, quartz-diorite and tonalite. The iron enrichment and inferred saturation sequence of chr+ol-plag-cpx-mt-ap-zr are characteristic of low-oxygen fugacity, tholeiitic MORB and continental margin intrusions. In this, and more easily in other, smaller sill- and dyke-like bodies, we can use these proxy diagrams to identify rocks representative of liquid (non-cumulate) compositions, equivalent to the chilled facies of classic intrusions. Although these also follow fluid- and melt-infiltration vectors, especially around silica-rich rocks which reached melting temperatures, a small number of unmodified liquid compositions can be identified. These allow the setting to be determined using Th-Nb-Ti-Yb systematics. In this case, the data mostly plot in the centre of the MORB-OIB array on a Th/Yb-Nb-Yb plot indicating undepleted mantle. Some samples plot to higher Th/Yb indicating limited crustal assimilation. The samples plot in the MORB, rather than OIB, field on a Ti/Yb-Nb/Yb plot indicating shallow-melting indicative of thin lithosphere. Thus, an origin at a volcanic-rifted continental margin may be inferred. This procedure can also be applied to the debate over the origin and settings of eclogite inclusions in kimberlites.

Pearce, J. A.; Robinson, P.; Yang, J.

2011-12-01

190

Temperature dependence of magnetic EXAFS for rare earth elements  

Microsoft Academic Search

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

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

2005-01-01

191

Magnetism of silicon doped with alkaline earth elements  

Microsoft Academic Search

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

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

2005-01-01

192

Trace element cycling in a subterranean estuary: Part 1. Geochemistry of the permeable sediments  

NASA Astrophysics Data System (ADS)

Subterranean estuaries are characterized by the mixing of terrestrially derived groundwater and seawater in a coastal aquifer. Subterranean estuaries, like their river water-seawater counterparts on the surface of the earth, represent a major, but less visible, hydrological and geochemical interface between the continents and the ocean. This article is the first in a two-part series on the biogeochemistry of the subterranean estuary at the head of Waquoit Bay (Cape Cod, MA, USA). The pore-water distributions of salinity, Fe and Mn establish the salt and redox framework of this subterranean estuary. The biogeochemistry of Fe, Mn, P, Ba, U and Th will be addressed from the perspective of the sediment composition. A second article will focus on the groundwater and pore-water chemistries of Fe, Mn, U and Ba. Three sediment cores were collected from the head of Waquoit Bay where the coastal aquifer consists of permeable sandy sediment. A selective dissolution method was used to measure the concentrations of P, Ba, U and Th that are associated with “amorphous (hydr)oxides of iron and manganese” and “crystalline Fe and Mn (hydr)oxides.” The deeper sections of the cores are characterized by large amounts of iron (hydr)oxides that are precipitated onto organic C-poor quartz sand from high-salinity pore waters rich in dissolved ferrous iron. Unlike Fe (hydr)oxides, which increase with depth, the Mn (hydr)oxides display midcore maxima. This type of vertical stratification is consistent with redox-controlled diagenesis in which Mn (hydr)oxides are formed at shallower depths than iron (hydr)oxides. P and Th are enriched in the deep sections of the cores, consistent with their well-documented affinity for Fe (hydr)oxides. In contrast, the downcore distribution of Ba, especially in core 3, more closely tracks the concentration of Mn (hydr)oxides. Even though Mn (hydr)oxides are 200 300 times less abundant than Fe (hydr)oxides in the cores, Mn (hydr)oxides are known to have an affinity for Ba which is many orders of magnitude greater than iron (hydr)oxides. Hence, the downcore distribution of Ba in Fe (hydr)oxide rich sediments is most probably controlled by the presence of Mn (hydr)oxides. U is enriched in the upper zones of the cores, consistent with the formation of highly reducing near-surface sediments in the intertidal zone at the head of the Bay. Hence, the recirculation of seawater through this type of subterranean estuary, coupled with the abiotic and/or biotic reduction of soluble U(VI) to insoluble U(IV), leads to the sediments acting as a oceanic net sink of U. These results highlight the importance of permeable sediments as hosts to a wide range of biogeochemical reactions, which may be impacting geochemical budgets on scales ranging from coastal aquifers to the continental shelf.

Charette, Matthew A.; Sholkovitz, Edward R.; Hansel, Colleen M.

2005-04-01

193

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

Microsoft Academic Search

We present detailed experimental results on the partitioning of rare earth elements (REE) between titanite and a range of different silicate melts. Our results show that Henry’s law of trace element partitioning depends on bulk composition, the available partners for heterovalent substitution, crystal composition, and melt composition. We illustrate that the partition coefficients for Sm depend very strongly on the

Stefan Prowatke; Stephan Klemme

2006-01-01

194

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

Microsoft Academic Search

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

Jörg Hermann

2002-01-01

195

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

Microsoft Academic Search

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

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

1985-01-01

196

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

Microsoft Academic Search

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

Meenakshi Wadhwa; Ghislaine Crozaz

1998-01-01

197

Distribution of titanium and the rare earth elements between peridotitic minerals  

Microsoft Academic Search

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

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

1992-01-01

198

Rare earth element complexation by carbonate and oxalate ions  

NASA Astrophysics Data System (ADS)

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

Cantrell, Kirk J.; Byrne, Robert H.

1987-03-01

199

Rare-earth elements in heat-treatable steels  

SciTech Connect

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

Zhang, S.; Wu, C.

1986-01-01

200

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

PubMed

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

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

2007-01-12

201

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

Microsoft Academic Search

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

Martin J. Whitehouse; Balz S. Kamber

2002-01-01

202

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

Microsoft Academic Search

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

Bernard J. Wood; Jonathan D. Blundy

1997-01-01

203

Interoperability of Databases in the Cyberinfrastructure for Geochemistry: Identifying and Retrieving Related Records Between LEPR and EarthChem  

NASA Astrophysics Data System (ADS)

EarthChem (www.earthchem.org) is a portal that currently aggregates chemical data on igneous rock compositions from the GEOROC, NAVDAT, PetDB and USGS databases. LEPR (lepr.ofm-research.org) is a database of phase compositions compiled from experimental studies of liquid-solid equilibria relevant to the origin and evolution of magmatic systems. We have developed search algorithms, web services and an interface to these services, that permit the identification and retrieval of data between the LEPR and EarthChem collections. The tools we have developed establish an important level of interoperability between these database resources and permit a number of research questions to be pursued that otherwise could not be addressed. For example, users of EarthChem, having identified a suite of rocks on the basis of geographic location or chemical characteristics, may now inquire and retrieve experimental data from LEPR pertaining to these rocks, which in turn may help illuminate the physical conditions associated with their petrogenesis. Alternately, run products of experimental studies of the liquid line of descent of various source compositions in LEPR may now be identified with natural samples of rocks in EarthChem, which potentially expands the relevance and applicability of the original laboratory study beyond its primary objective. The methods implemented to identify commonalities across data sources include multivariate bracketed searchers and multivariate “nearest neighbor” (NN) searchers. For the latter, a weighted Euclidian distance measure is constructed comparing target compositions against all database entries, with results ordered by ascending “distance.” The NN searchers have proved most effective in exploring degree of overlap or lack thereof between LEPR and EarthChem records.

Ghiorso, M. S.; Walker, D.; Ash, J. M.

2009-12-01

204

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

Microsoft Academic Search

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

Hiroaki Onoda; Kazuo Kojima; Hiroyuki Nariai

2006-01-01

205

The Toxicological Geochemistry of Dusts, Soils, and Other Earth Materials: Insights From In Vitro Physiologically-based Geochemical Leach Tests  

NASA Astrophysics Data System (ADS)

Exposure to mineral dusts, soils, and other earth materials results in chemical reactions between the materials and different body fluids that include, depending upon the exposure route, lung fluids, gastrointestinal fluids, and perspiration. In vitro physiologically-based geochemical leach tests provide useful insights into these chemical reactions and their potential toxicological implications. We have conducted such leach tests on a variety of earth materials, including asbestos, volcanic ash, dusts from dry lake beds, mine wastes, wastes left from the roasting of mercury ores, mineral processing wastes, coal dusts and coal fly ash, various soils, and complex dusts generated by the World Trade Center collapse. Size-fractionated samples of earth materials that have been well-characterized mineralogically and chemically are reacted at body temperature (37 C) for periods from 2 hours up to multiple days with various proportions of simulated lung, gastric, intestinal, and/or plasma-based fluids. Results indicate that different earth materials may have quite different solubility and dissolution behavior in vivo, depending upon a) the mineralogic makeup of the material, and b) the exposure route. For example, biodurable minerals such as asbestos and volcanic ash particles, whose health effects result because they dissolve very slowly in vivo, bleed off low levels of trace metals into the simulated lung fluids; these include metals such as Fe and Cr that are suspected by health scientists of contributing to the generation of reactive oxygen species and resulting DNA damage in vivo. In contrast, dry lake bed dusts and concrete-rich dusts are highly alkaline and bioreactive, and cause substantial pH increases and other chemical changes in the simulated body fluids. Many of the earth materials tested contain a variety of metals that can be quite soluble (bioaccessible), depending upon the material and the simulated body fluid composition. For example, due to their acidic pH and high chloride concentrations, simulated gastric fluids are most efficient at solubilizing metals such as Hg, Pb, Zn, and others that form strong chloride complexes; although these metals tend to partially reprecipitate in the near-neutral simulated intestinal fluids, complexes with organic ligands (i.e., amino and carboxylic acids) enhance their solubility. These metals are also quite soluble in near-neutral, protein-rich plasma-based fluids because they form strong complexes with the proteins. In contrast, metalloids that form oxyanion species (such as As, Cr, Mo, W) are commonly more soluble in near-neutral pH simulated lung fluids than in simulated gastric fluids.

Plumlee, G. S.; Ziegler, T. L.; Lamothe, P.; Meeker, G. P.; Sutley, S.

2003-12-01

206

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

Microsoft Academic Search

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

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

2000-01-01

207

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

Microsoft Academic Search

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

Martin J Whitehouse; Balz S Kamber

2002-01-01

208

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

SciTech Connect

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

Kim, A.S.

1992-02-25

209

Petrology and trace element geochemistry of Robert Massif 04261 and 04262 meteorites, the first examples of geochemically enriched lherzolitic shergottites  

NASA Astrophysics Data System (ADS)

Shergottites sampled two distinct geochemical reservoirs on Mars. Basaltic and olivine-phyric shergottites individually sampled both geochemically enriched and depleted reservoirs, whereas lherzolitic shergottites are previously known only to exhibit a relatively limited intermediate geochemical signature that may have resulted from the mixing of the two geochemical end-member reservoirs. Here we show that recently discovered shergottites Robert Massif (RBT) 04261 and RBT 04262 are the first examples of lherzolitic shergottites originating from the enriched reservoir. RBT 04261 and RBT 04262, initially identified as olivine-phyric shergottites, are actually lherzolitic shergottites. Both meteorites exhibit nearly identical textures and mineral compositions, suggesting that they should be paired. Each consists of two distinct textures: poikilitic and non-poikilitic. The poikilitic areas are composed of pyroxene oikocrysts enclosing olivine grains; all pyroxene oikocrysts have pigeonite cores mantled by augite. The non-poikilitic areas are composed of olivine, pyroxene, maskelynite and minor amounts of merrillite, chromite and ilmenite. Olivine and pyroxene show the lowest Mg-number, and maskelynite has the lowest anorthite component among the lherzolitic shergottites. Moreover, the modal abundances of maskelynite in these two meteorites are distinctly higher than the other lherzolitic shergottites. The rare earth element (REE) budgets of RBT 04261 and RBT 04262 are dominated by merrillite. The slightly light rare earth element (LREE)-enriched pattern of this mineral is similar to that of merrillite in the geochemically enriched basaltic shergottites Shergotty and Zagami, and unlike the LREE-depleted pattern of merrillite in the other lherzolitic shergottites. The REE patterns of both high- and low-Ca pyroxenes are also similar to those in Shergotty and Zagami. The REE pattern of a melt calculated to be in equilibrium with the core of a pyroxene oikocryst is parallel to that of the RBT 04262 whole-rock as well as whole-rock compositions of other geochemically enriched basaltic shergottites. These observations imply that RBT 04262 sampled an enriched and oxidized reservoir similar to that sampled by some of the basaltic shergottites and are consistent with an oxidizing condition for the formation of RBT 04262 (log fO 2 = QFM-1.6). The petrographic and geochemical observations presented here suggest that RBT 04261 and RBT 04262 represent the most evolved magma among the lherzolitic shergottites and that this magma originated from a geochemically enriched reservoir on Mars. Based on an evaluation of the relationship between petrographic, geochemical and chronological signatures for shergottites including RBT 04261 and RBT 04262, we propose that both geochemically enriched and depleted shergottites were ejected from the same launch site on Mars.

Usui, Tomohiro; Sanborn, Matthew; Wadhwa, Meenakshi; McSween, Harry Y., Jr.

2010-12-01

210

Trace element and isotope geochemistry of depleted peridotites from an N-MORB type ophiolite (Internal Liguride, N. Italy)  

NASA Astrophysics Data System (ADS)

Mantle peridotites of the Internal Liguride (IL) units (Northern Apennines) constitute a rare example of the depleted lithosphere of the Jurassic Ligurian Tethys. Detailed chemical (ICP-MS and SIMS techniques) and isotopic investigations on very fresh samples have been performed with the major aim to constrain the timing and mechanism of their evolution and to furnish new data for the geodynamic interpretation. The data are also useful to discuss some general geochemical aspects of oceanic-type mantle. The studied samples consist of clinopyroxene-poor spinel lherzolites, showing incipient re-equilibration in the plagioclase-facies stability field. The spinel-facies assemblage records high (asthenospheric) equilibration temperatures (1150 1250° C). Whole rocks, and constituent clinopyroxenes, show a decoupling between severe depletion in highly incompatible elements [light rare earth elements (LREE), Sr, Zr, Na, Ti] and less pronounced depletion in moderate incompatible elements (Ca, Al, Sc, V). Bulk rocks also display a relatively strong M(middle)REE/H(heavy)REE fractionation. These compositional features indicate low-degree (<10%) fractional melting, which presumably started in the garnet stability field, as the most suitable depletion mechanism. In this respect, the IL ultramafics show strong similarity to abyssal peridotites. The Sr and Nd isotopic compositions, determined on carefully handpicked clinopyroxene separates, indicate an extremely depleted signature (87Sr/86Sr=0.702203 0.702285; 143Nd/144Nd=0.513619 0.513775). The Sm/Nd model ages suggest that the IL peridotites melted most likely during Permian times. They could record, therefore, the early upwelling and melting of mid ocean ridge basalt (MORB) type asthenosphere, in response to the onset of extensional mechanisms which led to the opening of the Western Tethys. They subsequently cooled and experienced a composite subsolidus evolution testified by multiple episodes of gabbroic intrusions and H T-L P retrograde metamorphic re-equilibration, prior to their emplacement on the sea floor. The trace element chemistry of IL peridotites also provides useful information about the composition of oceanic-type mantle. The most important feature concerns the occurrence of Sr and Zr negative anomalies (relative to “adjacent” REE) in both clinopyroxenes and bulk rocks. We suggest that such anomalies reflect changes in the relative magnitude of Sr, Zr and REE partition coefficients, depending on the specific melting conditions.

Rampone, E.; Hofmann, A. W.; Piccardo, G. B.; Vannucci, R.; Bottazzi, P.; Ottolini, L.

1996-02-01

211

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

SciTech Connect

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

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

2000-06-01

212

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

Microsoft Academic Search

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

Shen-Su Sun; Robert W. Nesbitt

1978-01-01

213

Controls on the distribution of rare earth elements in shallow groundwaters  

Microsoft Academic Search

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

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

2004-01-01

214

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

Microsoft Academic Search

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

M. Ghaderi

2001-01-01

215

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

Microsoft Academic Search

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

Glenn A. Gaetani; Timothy L. Grove

1995-01-01

216

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

SciTech Connect

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

Wills, J.W.; Eriksson, O.

1996-07-01

217

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

Microsoft Academic Search

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

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

1995-01-01

218

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

Microsoft Academic Search

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

V. P. Shvedov; A. V. Stepnov

1959-01-01

219

Cerium redox cycles and rare earth elements in the Sargasso Sea  

Microsoft Academic Search

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

E. R. Sholkovitz; D. L. Schneider

1991-01-01

220

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

Microsoft Academic Search

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

Jan Olov Nyström

1984-01-01

221

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

Microsoft Academic Search

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

C. Pride; G. K. Muecke

1981-01-01

222

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

Microsoft Academic Search

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

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

1997-01-01

223

Microdistributions and petrogenetic implications of rare earth elements in polymict ureilites  

Microsoft Academic Search

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

Yunbin Guan; Ghislaine Crozaz

2001-01-01

224

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

National Technical Information Service (NTIS)

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

E. A. Jones

1978-01-01

225

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

National Technical Information Service (NTIS)

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

M. M. Weiner

1992-01-01

226

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

National Technical Information Service (NTIS)

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

M. M. Weiner

1990-01-01

227

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

Microsoft Academic Search

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

D. P. Rubincam

2002-01-01

228

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

Microsoft Academic Search

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

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

1998-01-01

229

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

Microsoft Academic Search

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

T. H. Green; N. J. Pearson

1985-01-01

230

Rare earth elements in soil and in soil-grown plants  

Microsoft Academic Search

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

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

1998-01-01

231

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

Microsoft Academic Search

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

N. Shimizu

1975-01-01

232

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

Microsoft Academic Search

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

W. V. Boynton

1975-01-01

233

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

Microsoft Academic Search

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

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

1987-01-01

234

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

Microsoft Academic Search

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

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

1990-01-01

235

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

Microsoft Academic Search

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

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

1999-01-01

236

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

Microsoft Academic Search

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

N. Shimizu; I. Kushiro

1975-01-01

237

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

Microsoft Academic Search

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

Niels Crosley Munksgaard; Kezia Lim; David Livingstone Parry

2003-01-01

238

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

Microsoft Academic Search

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

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

1988-01-01

239

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

Microsoft Academic Search

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

Abeer Yassin; Robert Castanet

2001-01-01

240

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

Microsoft Academic Search

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

Judith Wright; Hans Schrader; William T. Holser

1987-01-01

241

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

National Technical Information Service (NTIS)

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

N. N. Stefanovich

1965-01-01

242

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

Microsoft Academic Search

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

E. O. Chaljub; J. Vilotte

2001-01-01

243

Seasonality of dissolved rare earth elements in the lower Mississippi River  

Microsoft Academic Search

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

Alan M. Shiller

2002-01-01

244

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

EPA Science Inventory

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

245

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

Microsoft Academic Search

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

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

2004-01-01

246

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

National Technical Information Service (NTIS)

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

S. A. Wood

2001-01-01

247

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

Microsoft Academic Search

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

Amr A. Sharaf

1993-01-01

248

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

Microsoft Academic Search

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

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

249

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

National Technical Information Service (NTIS)

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

G. V. Shishalova T. A. Nazarenko

1980-01-01

250

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

Microsoft Academic Search

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

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

2008-01-01

251

The aquatic chemistry of rare earth elements in rivers and estuaries  

Microsoft Academic Search

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

Edward R. Sholkovitz

1995-01-01

252

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

SciTech Connect

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

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

1985-04-20

253

U-Pb SHRIMP geochronology and trace-element geochemistry of coesite-bearing zircons, North-East Greenland Caledonides  

USGS Publications Warehouse

Obtaining reliable estimates for the timing of eclogite-facies metamorphism is critical to establishing models for the formation and exhumation of high-pressure and ultrahigh-pressure (UHP) metamorphic terranes in collisional orogens. The presence of pressure-dependent phases, such as coesite, included in metamorphic zircon is generally regarded as evidence that zircon growth occurred at UHP conditions and, ifdated, should provide the necessary timing information. We report U-Pb sensitive high-resolution ion microprobe (SHRIMP) ages and trace-element SHRIMP data from coesite-bearing zircon suites formed during UHP metamorphism in the North- East Greenland Caledonides. Kyanite eclogite and quartzofeldspathic host gneiss samples from an island in J??kelbugt (78??00'N, 18??04'W) contained subspherical zircons with well-defined domains in cathodoluminescence (CL) images. The presence of coesite is confirmed by Raman spectroscopy in six zircons from four samples. Additional components of the eclogite-facies inclusion suite include kyanite, omphacite, garnet, and rutile. The trace-element signatures in core domains reflect modification of igneous protolith zircon. Rim signatures show flat heavy rare earth element (HREE) patterns that are characteristic of eclogite-facies zircon. The kyanite eclogites generally lack a Eu anomaly, whereas a negative Eu anomaly persists in all domains of the host gneiss. The 207Pb- corrected 206Pb/238U ages range from 330 to 390 Ma for the host gneiss and 330-370 Ma for the kyanite eclogite. Weighted mean 206Pb/238U ages for coesite-bearing domains vary from 364 ?? 8 Ma for the host gneiss to 350 ?? 4 Ma for kyanite eclogite. The combined U-Pb and REE data interpreted in conjunction with observed CL domains and inclusion suites suggest that (1) Caledonian metamorphic zircon formed by both new zircon growth and recrystallization, (2) UHP metamorphism occurred near the end of the Caledonian collision, and (3) the 30-50m.y. span of ages records long residence times at eclogite-facies conditions for the UHProcks of North-East Greenland. This spread in observed ages is interpreted to be characteristic of metamorphic rocks that have experienced relatively long (longer than 10 m.y.) residence times at UHP conditions. ?? 2006 Geological Society of America.

McClelland, W. C.; Power, S. E.; Gilotti, J. A.; Mazdab, F. K.; Wopenka, B.

2006-01-01

254

Highly siderophile element geochemistry of 187Os-enriched 2.8 Ga Kostomuksha komatiites, Baltic Shield  

NASA Astrophysics Data System (ADS)

New analyses of highly siderophile elements (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 element 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 Earth'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 elemental abundance pattern in the mantle source of Kostomuksha komatiites.

Puchtel, Igor S.; Humayun, Munir

2005-03-01

255

Oceanic crustal thickness from seismic measurements and rare earth element inversions  

SciTech Connect

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

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

1992-12-10

256

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

Microsoft Academic Search

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

P. C. Rankin; C. W. Childs

1987-01-01

257

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

Microsoft Academic Search

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

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

2005-01-01

258

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

Microsoft Academic Search

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

Weiwei WAN; Jianmin HAN; Weijing LI; Jinhua WANG

2006-01-01

259

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

260

Seasonality of Rare Earth Element concentrations and fluxes in the Amazon river and its main tributaries  

Microsoft Academic Search

Many studies carried out on the Amazon River illustrate the complex functioning of this river in terms of geochemistry. Concerning the REE, (Sholkovitz and Szymczak 2000) and (Hannigan and Sholkovitz 2001, Gerard et al, 2003) summarized the actual knowledge we have on the Amazon river. In this study we present a 2-year time series on dissolved REE geochemistry in the

P. Seyler; J. Sonke; J. Viers; G. Barroux; G. R. Boaventura; T. Rousseau

2008-01-01

261

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

SciTech Connect

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

Nesterova, M.D.

1986-08-01

262

Geochemistry and the Environment. Volume II. The Relation of Other Selected Trace Elements to Health and Disease.  

National Technical Information Service (NTIS)

The second volume of a trilogy continues the consideration of possible relationships between the geographic distribution of certain elements and patterns of disease. In the individual reports on trace elements related to health and disease, the elements b...

1977-01-01

263

Platinum-group element geochemistry of the Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in western Yangtze Block, SW China: control of platinum-group elements by magnetite  

NASA Astrophysics Data System (ADS)

Platinum-group element (PGE) geochemistry combined with elemental geochemistry 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 elements 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 elements 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.

Fan, Hong-Peng; Zhu, Wei-Guang; Zhong, Hong; Bai, Zhong-Jie; He, De-Feng; Ye, Xian-Tao; Chen, Cai-Jie; Cao, Chong-Yong

2013-09-01

264

Exploration Geochemistry.  

ERIC Educational Resources Information Center

|Contributions in mineral-deposit model formulation, geochemical exploration in glaciated and arid environments, analytical and sampling problems, and bibliographic research were made in symposia held and proceedings volumes published during 1982. Highlights of these symposia and proceedings and comments on trends in exploration geochemistry are…

Closs, L. Graham

1983-01-01

265

Radiogenic isotopes: systematics and applications to earth surface processes and chemical stratigraphy  

Microsoft Academic Search

Radiogenic isotopes have wide application to chemical stratigraphy, geochronology, provenance studies, and studies of temporal changes in Earth surface processes. This paper briefly reviews the principles of radiogenic isotope geochemistry and the distribution of a number of elements of interest in the environment, and then uses this information to explore the range of applications to chemical stratigraphy and other fundamental

Jay L. Banner

2004-01-01

266

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

SciTech Connect

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

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

2011-01-01

267

Anais do 2. Congresso Brasileiro de Geoquimica. (Proceedings of 2. Brazilian Geochemical Congress).  

National Technical Information Service (NTIS)

Some works about geochemistry are presented, including themes about geochemical exploration, lithogeochemistry and isotope geochemistry, environmental geochemistry, analytical geochemistry, geochemistry of carbonatites and rare earth elements and organic ...

1989-01-01

268

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

Microsoft Academic Search

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

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

2007-01-01

269

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

NASA Astrophysics Data System (ADS)

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

Schönbächler, M.; Nimmo, F.

2011-12-01

270

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

Microsoft Academic Search

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

Shuzhen Zhang; Xiao-Quan Shan; Fuliang Li

2000-01-01

271

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

Microsoft Academic Search

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

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

2001-01-01

272

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

Microsoft Academic Search

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

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

1995-01-01

273

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

Microsoft Academic Search

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

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

1999-01-01

274

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

Microsoft Academic Search

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

Paul W. O. Hoskin; Trevor R. Ireland

2000-01-01

275

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

Microsoft Academic Search

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

C Guy; V Daux; J Schott

1999-01-01

276

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

Microsoft Academic Search

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

Michael Bau; Peter Dulski

1995-01-01

277

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

Microsoft Academic Search

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

Karl E. Seifert; Sarah A. Chadima

1989-01-01

278

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

Microsoft Academic Search

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

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

279

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

Microsoft Academic Search

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

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

2004-01-01

280

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

Microsoft Academic Search

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

Huang Zhilong; Zhu Chengming; Wang Liankui

1996-01-01

281

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

Microsoft Academic Search

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

Yongxing Wang; Min Zhang; Xiaorong Wang

2000-01-01

282

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

Microsoft Academic Search

Sargasso Sea suspended particles were sequentially digested with three chemical treatments (acetic acid, mild HCl\\/HNO[sub 3], and HF\\/HNO[sub 3]\\/HCl in a bomb). The latter two treatments dissolve detrital minerals, while the acetic acid removes surface coatings (organic matter and Mn oxides). The rare earth element (REE) composition of the surface coatings, in marked contrast to the crust-like REE composition of

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

1994-01-01

283

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

Microsoft Academic Search

Sargasso Sea suspended particles were sequentially digested with three chemical treatments (acetic acid, mild HCl\\/HNO 3 and HF\\/HNO 3 \\/HCl in a bomb). The latter two treatments dissolve detrital minerals, while the acetic acid removes surface coatings (organic matter and Mn oxides). The rare earth element (REE) composition of the surface coatings, in marked contrast to the crust-like REE composition

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

1994-01-01

284

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

Microsoft Academic Search

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

Jong Hyeon Lee; R. H. Byrne

1993-01-01

285

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

Microsoft Academic Search

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

Gregory E. Webb; Balz S. Kamber

2000-01-01

286

Behaviour of rare earth elements during submarine weathering of tholeiitic basalt  

Microsoft Academic Search

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

John N. Ludden; Geoffrey Thompson

1978-01-01

287

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

Microsoft Academic Search

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

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

1999-01-01

288

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

Microsoft Academic Search

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

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

1992-01-01

289

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

Microsoft Academic Search

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

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

1984-01-01

290

Oceanic crustal thickness from seismic measurements and rare earth element inversions  

Microsoft Academic Search

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

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

1992-01-01

291

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

Microsoft Academic Search

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

Hiroshi Maeda; Yoshiaki Tanaka; Masao Fukutomi; Toshihisa Asano

1988-01-01

292

Removal of Rare Earth Elements and Precious Metal Species by Biosorption  

Microsoft Academic Search

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

Yves Andrès; Claire Gérente

293

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

Microsoft Academic Search

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

G. M. Kolesov; V. I. Fernadsky

1976-01-01

294

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

Microsoft Academic Search

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

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

2010-01-01

295

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

Microsoft Academic Search

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

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

2008-01-01

296

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

Microsoft Academic Search

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

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

1997-01-01

297

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

Microsoft Academic Search

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

P. H. OlinJ; J. A. Wolff

2010-01-01

298

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

Microsoft Academic Search

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

Mingjia WANG; Yanmei LI; Zixi WANG; Er BAO

2011-01-01

299

EarthRef: Website for Physical and Chemical Earth References  

NSDL National Science Digital Library

The EarthRef web site contains several online databases, downloadable modeling tools, and more. The databases include GERM (Geochemical Earth Reference Model), the EarthRef Digital Archive, the Seamount Catalog, and Partition Coefficients. A Geophysical Reference Earth Model (REM) is currently under construction. The GERM database contains summary data on the geochemistry of all reservoirs in the Earth and solar system. It includes only peer-reviewed data and is searchable by reservoir, element, and reference. The EarthRef Digital Archive contains any type of digital data object associated with the Earth Sciences. Data objects may be part of non-published Earth 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 element. Both experimental and empirical data are included in this extensive compilation.

300

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

PubMed Central

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

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

2008-01-01

301

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

PubMed

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

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

2012-02-29

302

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

PubMed

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

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

2003-04-24

303

Geochemistry Home  

NSDL National Science Digital Library

This project provides resources for teaching geochemistry. It includes an on-line tutorial of the analytical techniques commonly used to characterize geological materials, the goal of which is to help novices (such as students or scientists working out of their field) to gain an understanding of mineralogical, petrological and geochemical analytical techniques. There is also a collection of teaching activities and a geochemical instrument registry available on this site.

304

Continentally-derived solutes in shallow Archean seawater: Rare earth element and Nd isotope evidence in iron formation from the 2.9 Ga Pongola Supergroup, South Africa  

Microsoft Academic Search

The chemical composition of surface water in the photic zone of the Precambrian ocean is almost exclusively known from studies of stromatolitic carbonates, while banded iron formations (IFs) have provided information on the composition of deeper waters. Here we discuss the trace element and Nd isotope geochemistry of very shallow-water IF from the Pongola Supergroup, South Africa, to gain a

Brian W. Alexander; Michael Bau; Per Andersson; Peter Dulski

2008-01-01

305

Geochemistry for Chemists.  

ERIC Educational Resources Information Center

|A geochemistry course for chemists is described. Includes: (1) general course information; (2) subject matter covered; and (3) a consideration of the uses of geochemistry in a chemistry curriculum, including geochemical "real world" examples, geochemistry in general chemistry, and geochemistry as an elective. (JN)|

Hostettler, John D.

1985-01-01

306

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

National Technical Information Service (NTIS)

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

M. M. Weiner

1992-01-01

307

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

Microsoft Academic Search

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

M. M. Weiner

1992-01-01

308

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

Microsoft Academic Search

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

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

1996-01-01

309

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

Microsoft Academic Search

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

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

2006-01-01

310

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

Microsoft Academic Search

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

Xinde Cao; Ying Chen; Zhimang Gu; Xiaorong Wang

2000-01-01

311

Major-element geochemistry of the Silent Canyon-Black Mountain peralkaline volcanic centers, northwestern Nevada Test Site: applications to an assessment of renewed volcanism  

USGS Publications Warehouse

The Silent Canyon and Black Mountain volcanic centers are located in the northern part of the Nevada Test Site. The Silent Canyon volcanic center is a buried cauldron complex of Miocene age (13-15 m.y.). Black Mountain volcanic center is an elliptical-shaped cauldron complex of late Miocene age. The lavas and tuffs of the two centers comprise a subalkaline-peralkaline association. Rock types range from quartz normative subalkaline trachyte and rhyolite to peralkaline comendite. The Gold Flat Member of the Thirsty Canyon Tuff (Black Mountain) is a pantellerite. The major-element geochemistry of the Black Mountain-Silent Canyon volcanic centers differs in the total range and distribution of Si02, contents, the degree of peralkalinity (molecular Na2O+K2O>Al2O3) and in the values of total iron and alumina through the range of rock types. These differences indicate that the suites were unrelated and evolved from differing magma bodies. The Black Mountain volcanic cycle represents a renewed phase of volcanism following cessation of the Timber Mountain-Silent Canyon volcanic cycles. Consequently, there is a small but numerically incalculable probability of recurrence of Black Mountain-type volcanism within the Nevada Test Site region. This represents a potential risk with respect to deep geologic storage of high-level radioactive waste at the Nevada Test Site.

Crowe, Bruce M.; Sargent, Kenneth A.

1979-01-01

312

Provenance of late Oligocene to quaternary sediments of the Ecuadorian Amazonian foreland basin as inferred from major and trace element geochemistry and Nd-Sr isotopic composition  

NASA Astrophysics Data System (ADS)

Oligocene to Quaternary deposits from the Oriente Amazonian foreland basin (Ecuador and Peru) were analyzed for major and trace element geochemistry (46 and 32 samples respectively) and Nd-Sr isotopic systematics (n = 10). Chemical Index of Alteration values lower than those of other Amazonian foreland basin sediments and scattering along the AK join in the A-CN-K diagram indicate that the Oriente foreland basin has been continuously fed by poorly to moderately weathered sediments having an overall Andesitic composition since the Oligocene. Chemical ratios such as Cr/Th and Th/Sc as well as Eu anomaly and Nd-Sr isotopic compositions indicate that most of the analyzed sediments contained a greater proportion of volcanic arc rock material than the other Amazonian foreland basin sediments. When compared with the older sediments The Quaternary sediments are characterized by a greater contribution of the volcanic arc source. The composition of the sediments deposited in the Ecuadorian Amazonian foreland basin is mainly controlled by geodynamic processes. We suspect the Late Pliocene-Pleistocene subduction of the Carnegie ridge to be responsible for the back arc volcanism feeding the Amazonian foreland with more basic materials. Input of young Ecuadorian volcanic rocks may explain the difference in Sr and Nd isotopic ratios of suspended sediments between the Solimoes and the Madeira rivers.

Roddaz, Martin; Christophoul, Frédéric; Burgos Zambrano, José David; Soula, Jean-Claude; Baby, Patrice

2012-08-01

313

Radon (222Rn) level variations on a regional scale: influence of the basement trace element (U, Th) geochemistry on radon exhalation rates.  

PubMed

The approach proposed in this study provides insight into the influence of the basement geochemistry 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 element (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

Ielsch, G; Thiéblemont, D; Labed, V; Richon, P; Tymen, G; Ferry, C; Robé, M C; Baubron, J C; Béchennec, F

2001-01-01

314

MAJOR AND TRACE ELEMENTS GEOCHEMISTRY IN THE GROUND WATERS OF A VOLCANIC AREA: MOUNT ETNA (SICILY, ITALY)  

Microsoft Academic Search

Thirty-five ground-water samples have been collected from wells, springs and drainage galleries on Mt Etna volcano for the determination of major, minor and trace elements in solution. Attention has been focused in particular on dissolved minor and trace elements, for most of which no data were available in the studied area. In general, dissolution of solids into Etna's ground waters

SALVATORE GIAMMANCO; MASSIMO OTTAVIANI; MARIANO VALENZA; ENRICO VESCHETTI; EDOARDO PRINCIPIO; GIUSEPPE GIAMMANCO; SARINA PIGNATO

1998-01-01

315

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

PubMed

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

El-Taher, A

2007-01-08

316

Trace element geochemistry of the Jurassic coals in the Feke and Kozan (Adana) Areas, Eastern Taurides, Turkey  

SciTech Connect

In this study, trace element and organic matter-trace element 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 element 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 element 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 element concentrations are different for each of three fields. The major element 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 element contents of the world and U.S. coals, Ba is considerably high, Cu and Zr are moderately high, and Ga, Rb, and Sc elements 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 elements, 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 elements are enriched with respect to upper crust.

Kara-Gulbay, R.; Korkmaz, S. [Karadeniz Technical University, Trabzon (Turkey). Faculty of Engineering

2009-07-01

317

Metallogenic epoch of the Jiapigou gold belt, Jilin Province, China: Constrains from rare earth element, fluid inclusion geochemistry and geochronology  

NASA Astrophysics Data System (ADS)

The Jiapigou gold belt is located on the northern margin of the North China Craton, and is one of the most important gold-mining and production regions in the circum-Pacific metallogenic zone. Research has been conducted in this area since the 1960s, however, the timing of the gold mineralisation is still unresolved, and an ideal metallogenic model has not been well established. To address these questions, a systematic geological, geochemical and geochronological investigation was conducted. The study revealed that (i) the gold-bearing quartz veins can be divided into two groups, earlier and later gold-bearing quartz veins according to their occurrence and the geochemical characteristics, (ii) the geochemical characteristics of the ore bodies, while similar to granite, are clearly different from the altered rock, and (iii) the geochemical characteristics of the later gold-bearing quartz veins have more similarity to the altered rock than the earlier gold-bearing quartz veins do. Therefore, we conclude that two independent stages of metallogenesis within the Jiapigou gold deposit area are related to magmatic activity in the Palaeoproterozoic and the Yanshanian stage of the Mesozoic, that the ore-forming fluids are mainly of magmatic origin, and that magma contamination by the altered rock was stronger in the Mesozoic. Zircon LA-ICP-MS U-Pb data show that the age of the Palaeoproterozoic granite is ~2426.0 Ma and that of the Mesozoic granite is ~166.2 Ma; these ages can be interpreted as the maximum ages of the two periods of gold mineralisation. In addition to investigating the geotectonic and regional structure of the Jiapigou gold belt, this study also proposes that the WNW-trending zone of gold mineralisation is a result of a magmatic event within the basement in the early Palaeoproterozoic, and that large-scale sinistral strike-slip displacements of the Huifahe and Liangjiang Faults in the late Middle Triassic (Yanshanian epoch) controlled the later tectono-magmatic event and the NNE-ENE-trending zone of gold mineralisation.

Huang, Zhixin; Yuan, Wanming; Wang, Changming; Liu, Xiangwei; Xu, Xiaotong; Yang, Liya

2012-12-01

318

Rare Earth Elements Geochemistry of Laowan Gold Deposit in Henan Province: Trace to Source of Ore-Forming Materials  

Microsoft Academic Search

The compositions of REE in quartz and pyrite from the main stage of the Laowan gold deposit in Henan Province and that in quartz from Laowan granite were determined by inductively coupled plasma-mass-spectrometry (ICP-MS) to trace the source of ore-forming materials. Meanwhile, the REE compositions of the deposit ore, granite and metamorphic wall rock were also considered for comparative studies

Qiaoqin Xie; Xiaochun Xu; Xiaoxuan Li; Tianhu Chen; Sanming Lu

2006-01-01

319

Trace and Rare-Earth Element Geochemistry of the Karalar (Gazipafla—Antalya) Barite-Galena Deposits, Southern Turkey  

Microsoft Academic Search

The Karalar barite-galena deposits are typical examples of carbonate-hosted barite-galena deposits that occur widely in the central Taurides. Recent mining activity has been concentrated in the Büyük and Boyal›k mine areas. The mineralisation occurs as ore veins along fault zones and as ore-filled breccia zones along the strongly deformed lower walls of limestone blocks in the Permian limestones of the

GÜLCAN BOZKAYA; AHMET GÖKÇE; Nadir Toprak; Element Jeokimyas; Güney Türkiye

2004-01-01

320

Geochemistry of the rare earth elements in natural terrestrial waters: A review of what is currently known  

Microsoft Academic Search

The range of observed chemical compositions of natural terrestrial waters varies greatly especially when compared to the essentially\\u000a constant global composition of the oceans. The concentrations of the REEs in natural terrestrial waters also exhibit more\\u000a variation than what was reported in seawater. In terrestrial waters, pH values span the range from acid up to alkaline. In\\u000a addition, terrestrial waters

Zhou Xiaoping

1997-01-01

321

Geochemistry of polymetamorphic ultramafics (Major, Trace, Noble and Rare Earth Elements): An example from the Helvetic basement, Central Alps, Switzerland  

Microsoft Academic Search

Summary Polymetamorphic ultramafic rocks in orogenic terranes rarely preserve relic structures or minerals from their former mantle stages. The determination of their protoliths and their tectonic evolution by chemical discrimination methods is often difficult due to possible metasomatic processes. Ultramafics of the pre-Variscan Helvetic basement (Central Alps, Switzerland) have been investigated geochemically to address these problems. These ultramafics are partially

G. G. Büno; T. Meisel

1993-01-01

322

Earth Science Information System (ESIS)  

USGS Publications Warehouse

The Earth 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 elements 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, geochemistry, hydrology, cartography, oceanography, geography, minerals exploration and conservation, and satellite data sensing.

U.S. Geological Survey

1982-01-01

323

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

324

Contribution to the geochemistry of trace elements in the sediments of the Noun River and tributaries, western Cameroon.  

PubMed

This study reports on the distribution of trace elements in the sediments of the Noun River valley. Two groups of trace elements have emerged based on their distribution and geochemical behaviour. The first group shows lower values whereas the second group aligns higher values. Elements like Al and Sr in one side and Zn, Zr in the other present concentrations statistically different from those of the rocks compared to other elements in trace analyzed (Cr, Ni, Ba, Co, Cu, Fe, Mn, V, As and Pb). The trace elements Al, Sr, Zr, Zn and Pb in the sediments of the Noun River show concentrations rather lower than those of the world. The average concentrations in elements C (3.72%), N (0.27%), S (0.05%) and of the ratios C/N (13.77) and N/S (5.29) reflect those resulting from the decomposition of the organic matter which derives from soils with very small concentrations in S. The Noun valley sediments are mostly of primary (quartz, microcline, plagioclase, orthoclase, ilmenite, anatase) and newly formed or secondary (kaolinite, gibbsite, hematite, goethite) minerals. This mineralogy and the overall low concentration of the studied trace elements, with Al, Fe, Ti and Mn as most abundant elements, is consistent with the local geology made up of the basic rocks (basalts, volcanic ash) and of the acid rocks (granites, gneiss). Overall the trace elements concentration and distribution suggest their geogene origin. Yet, this study is a first contribution of its kind towards the development of a baseline geochemical database essential for a sustainable and healthier Noun valley ecosystem. PMID:19090098

Njofang, C; Matschullat, J; Tchouankoué, J P; Amougou, A

2007-09-15

325

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

NASA Astrophysics Data System (ADS)

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

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

326

Trace Element Geochemistry of Oceanic Peridotites and Silicate Melt Inclusions: Implications for Mantle Melting and Ocean Ridge Magmagenesis.  

National Technical Information Service (NTIS)

The mantle melting process is fundamental to describing basalt genesis and crustal accretion at mid-ocean ridges. The dissertation examines the trace element compositions of abyssal peridotites and discusses how they preserve details of the melting proces...

K. T. M. Johnson

1990-01-01

327

High-field-strength elements in carbonatitic rocks: Geochemistry, crystal chemistry and significance for constraining the sources of carbonatites  

Microsoft Academic Search

Carbonatites and related rocks exhibit a significant variation in their content of high-field-strength elements (HFSE), i.e. Ti, Nb, Ta, Zr and Hf. The average abundances of these elements (calculated for 119 localities worldwide) decrease from phoscorites and silicocarbonatites to calciocarbonatites to magnesiocarbonatites. The analytical data currently available for ferrocarbonatites are insufficient to establish if this trend persists through the entire

Anton R. Chakhmouradian

2006-01-01

328

Zircon trace element geochemistry: partitioning with garnet and the link between U–Pb ages and metamorphism  

Microsoft Academic Search

With the aim to link zircon composition with paragenesis and thus metamorphic conditions, zircons from eclogite- and granulite-facies rocks were analysed for trace elements using LA-ICP-MS and SHRIMP ion microprobe. Metamorphic zircons from these different settings display a large variation in trace element composition. In the granulites, zircon overgrowths formed in equilibrium with partial melt and are similar to magmatic

Daniela Rubatto

2002-01-01

329

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

330

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

Microsoft Academic Search

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

Xiong Yongliang; Zhai Yusheng

1991-01-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2002-04-01

332

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

333

Rare earth elements in the peats of Moscow and Tver oblasts  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

334

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

US Patent & Trademark Office Database

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

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

1985-11-12

335

Trace element geochemistry of scheelite and rutile from metaturbidite-hosted quartz vein gold deposits, Meguma Terrane, Nova Scotia, Canada: genetic implications  

NASA Astrophysics Data System (ADS)

Scheelite and rutile from several metaturbidite-hosted gold-bearing quartz vein deposits of the Meguma Terrane of Nova Scotia were analyzed for trace elements including rare earth elements, niobium and tantalum. Scheelites have high concentrations of Sr, Nb, Y and rare earth elements (REE) with bell-shaped chondrite-normalized REE patterns accompanied by both positive and negative Eu anomalies. They also have high Nb/Ta ratios (80-300). Three distinct trace element types of the scheelites are interpreted to reflect chemical differences in the pulses of hydrothermal fluids. Hydrothermal rutiles have high contents of W (up to 4.2 wt.% WO3), are rich in Ta compared to Nb and have a very low Nb/Ta ratio (~0.3). Hydrothermal fluids which produced both scheelite with a high Nb/Ta and rutile with a low Nb/Ta ratio are an efficient medium for fractionation of this ratio although these two minerals play an important role during the process.

Dostal, Jaroslav; Kontak, Daniel J.; Chatterjee, A. K.

2009-12-01

336

Geochemistry of trace elements in the extraterrestrial matter examined by the X-ray fluorescence method with synchrotron radiation  

NASA Astrophysics Data System (ADS)

X-ray fluorescence analysis with synchrotron radiation (XFA-SR) has been applied for the determination of incompatible trace elements (Rb, Sr, Y, Zr, Nb, Ba, La and Ce) in some extraterrestrial samples. A distribution of these elements in lunar whole rocks and their minerals, in the matrix, chondrules and Ca-Al-rich inclusions from various chondrites has been investigated. The XFA-SR analytical technique for very small objects ranging from 2 mm to 300 ?m has been described. The specific basaltic group of Luna-20, geochemically similar to Luna-24 VLT basalt, has been established. The points of intersection of the HAB-VHA rock trend and the TB rock trend on the bi-element correlation diagrams probably correspond to the concentration levels of these trace elements in the parent magmas. Distribution of trace elements in rock-forming minerals and in their host rocks showed two trends: early and late crystallizations with an inversion of the Y/Zr ratio. The difference in trace element distribution in chondrules, matrix and Ca-Al-rich inclusions from the chondrites has been shown. This indicates a varied genesis for these objects.

Tarasov, L. S.; Kudryashova, A. F.; Ivanov, A. V.; Ulyanov, A. A.; Baryshev, V. B.; Kulipanov, G. N.; Skrinsky, A. N.

1987-11-01

337

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

338

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

USGS Publications Warehouse

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

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

1981-01-01

339

The early Aptian OAE record in the Cau section (Prebetic Zone, Spain): High-resolution C-isotope stratigraphy, biomarker distributions, and elemental geochemistry  

NASA Astrophysics Data System (ADS)

The occurrence of time intervals of enhanced deposition of organic matter (OM) during the Cretaceous, defined as Oceanic Anoxic Events (OAE), reflect abrupt changes in global carbon cycling. These episodes raise questions about the causes for such perturbations, and their relation to fluctuations in ocean geochemistry, climate, and marine and continental biota. To investigate these questions, we have performed an integrated study comprising high-resolution C-isotope stratigraphy, biomarker distributions, and elemental geochemistry through the record of an expanded section of the OAE 1a (Cau section, Spain). This section belongs to the Prebetic Zone, which represents the platform domain of the Southern Iberian Paleomargin during the Mesozoic. The high-resolution C-isotope curve records the characteristic first negative and subsequent positive excursions that are well known from a large number of sections around the world. Apparent in the section are all eight of the segments previously defined from the alpine domain by Menegatti et al (1998). Both carbonate and organic C-isotope curves are presented and compared, allowing qualitative consideration for changes in pCO2. Molecular analyses of sedimentary organic matter are powerful tools in assessing the origin of organic matter and constraining ancient environmental conditions, such as marine productivity, anoxia in bottom waters or the photic zone and sea surface temperatures as well as its thermal maturity. The biomarker association in the section comprises mainly four main groups of compounds: n-alkanes, isoprenoids, hopanes and steranes. Overall, all of the OM present in the studied samples is interpreted to derive from significant terrestrial inputs as well as marine and bacterial sources. It is also thermally immature, leading to a good preservation of the organic compounds. This study has revealed major variations in biomarker distributions through the section, including the distributions of n-alkanes (long-chain versus short-chain compounds), relative abundances of n-alkanes, hopanes and steranes, and other significant biomarkers. These changes are interpreted to be related to variations in the major sources of the organic matter (bacterial, terrestrial and marine plants, marine plankton), and in the environmental conditions (i.e. development of water column stratification, anoxia and productivity). Elemental geochemical analyses have revealed major changes in redox-sensitive, productivity and provenance proxies through the section. The main contribution from these data is the observation of development of suboxic-anoxic conditions during the deposition of the OAE1a, with high frequency oscillations, especially during the onset of the event. Integration of C-isotopes, biomarkers and elemental distributions represents a powerful tool in the interpretation of the environmental changes that occurred during deposition of the OAE1a. Data presented here suggest significant sedimentary and biological perturbations predating the OAE1a, and environmental instability during especially the first stages of the OAE. Acknowledgements: This work is a contribution of the research project CGL2009-10329.

Castro, J. M.; Quijano, M. L.; de Gea, G. A.; Pancost, R. D.

2012-04-01

340

Biosorption of Uranium and Rare Earth Elements Using Biomass of Algae  

PubMed Central

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

Sakamoto, Nobuo; Kano, Naoki; Imaizumi, Hiroshi

2008-01-01

341

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

PubMed

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

Liu, Dongwu; Wang, Xue; Chen, Zhiwei

2012-02-01

342

The Geochemistry Of Major And Selected Trace Elements In A Forested Peat Bog, Kalimantan, SE-Asia, And Its Implications On Past Atmospheric Dust Deposition  

NASA Astrophysics Data System (ADS)

The major element geochemistry of a forested tropical peat deposit in SE Asia, was assessed by studying the vertical element distribution of Si, Al, Ti, Fe, Ca, Mg, K, Na, S and P in a 960 cm long, age-dated core profile. Peat formation started at c. 22,120 14C yr BP ago. Ca/Mg mass ratios of the solid peat are well below local rainwater values, which indicates a strongly ombrotrophic character throughout the deposit. This implies that most of the inorganic fraction has been supplied exclusively by atmospheric inputs. Concentration profiles of Mn, Sr, and Ca suggest that below 500 cm the influence from dissolving sediments is very minor. The elements Si, Ca, Mg, P, S and K show a strong and extended zone of enrichment in the top 200 cm of the profile, indicating that biological accumulation mechanisms are fundamentally different from temperate peats due to abundant pneumatophores. Despite the large forest cover, average concentrations for the entire profile are not elevated compared to temperate, non-forested peat cores. In the lower core sections, where the element distribution is dominated by past atmospheric deposition (200 - 845 cm), Al is on average neither depleted nor enriched relative to upper continental crust whereas Fe and Mg are slightly enriched and Ca, Si, K, and Na are strongly depleted. This favors highly weathered tropical soil dust as the main inorganic mineral source. Distinct tephra layers are absent within the profile despite the location of the study site within a tectonic active region. The concentration profiles for Si, Fe, Al, and Ti show five distinct peaks within the profile, implying enhanced dust deposition and/or reduced rates of peat accumulation, possibly owing to climatic changes during the Holocene. Enhanced dust deposition between c. 10,830 and 9,470 14C yr BP is tentatively interpreted as the Younger Dryas period with dust fluxes of c. 10.8 mg/m2/y. In addition, the Al/Ti and Fe/Ti profiles suggest that mineral dust sources have been changing constantly during the Holocene. Local sources were dominant between c. 7,820 to 9,470 14C yr BP and long range transport was important during the late Pleistocene/early Holocene and from 7,820 14C yr BP to present.

Weiss, D.; Weiss, D.; Shotyk, W.; Rieley, J. O.; Page, S. E.; Gloor, M.; Reese, S.; Cortizas-Martinez, A.

2001-12-01

343

Annual review of earth and planetary sciences. Volume 8  

SciTech Connect

Papers are presented on the geochemistry of evaporitic lacustrine deposits, the deformation of mantle rocks, the dynamics of sudden stratospheric warmings, the equatorial undercurrent, geomorphological processes on planetary surfaces, and rare earth elements in petrogenetic studies of igneous systems. Consideration is also given to evolutionary patterns in early Cenozoic animals, the origin and evolution of planetary atmospheres, the moons of Mars, and refractory inclusions in the Allende meteorite.

Donath, F.A.; Stehli, F.G.; Wetherill, G.W.

1980-01-01

344

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

SciTech Connect

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

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

1997-04-09

345

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

Microsoft Academic Search

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

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

2000-01-01

346

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

Microsoft Academic Search

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

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

1995-01-01

347

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

Microsoft Academic Search

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

TAIGA NAKAJIMA; YASUTAKA TERAKADO

348

Introduction to urban watershed geochemistry  

NSDL National Science Digital Library

The main goal of this multi-part field and lab exercise is to introduce students to practical aspects of soil and water geochemistry. Some of the analyses for this lab are conducted in the field using field analytical instruments and rest of the analyses is conducted in a wet chemistry/geochemistry lab. There are several objectives: 1. Learn how to sample water and soil samples in a safe and effective manner 2. Collect basic aqueous chemical parameters in the field 3. Compare field collected data with that obtained using advanced instruments in the laboratory 4. Determine bulk physical and chemical properties of the soils in the lab 5. Determine trace and major element concentrations of the soils in the laboratory At the end of this exercise students will gain a better appreciation for how soil and water quality is assessed in multiple ways. They are also introduced to basic "tools-of-the-trade" in the environmental geochemistry and also using Excel to make simple and advanced calculations as well as for plotting data. During preparation of lab reports, they are introduced to basic elements of an effective data-based technical paper. Key words: urban watershed, soil chemistry, water chemistry, aqueous geochemistry, field analysis, analytical chemistry

Vulava, Vijay

349

Medical geochemistry of tropical environments  

NASA Astrophysics Data System (ADS)

Geochemically, tropical environments are unique. This uniqueness stems from the fact that these terrains are continuously subjected to extreme rainfall and drought with resulting strong geochemical fractionation of elements. This characteristic geochemical partitioning results in either severe depletion of elements or accumulation to toxic levels. In both these situations, the effect on plant, animal and human health is marked. Medical geochemistry involves the study of the relationships between the geochemistry of the environment in which we live and the health of the population living in this particular domain. Interestingly, the relationships between geochemistry and health are most marked in the tropical countries, which coincidentally are among the poorest in the world. The very heavy dependence on the immediate environment for sustainable living in these lands enables the medical geochemist to observe correlations between particular geochemical provinces and the incidence of certain diseases unique to these terrains. The aetiology of diseases such as dental and skeletal fluorosis, iodine deficiency disorders, diseases of humans and animals caused by mineral imbalances among others, lie clearly in the geochemical environment. The study of the chemistry of the soils, water and stream sediments in relation to the incidence of geographically distributed diseases in the tropics has not only opened up new frontiers in multidisciplinary research, but has offered new challenges to the medical profession to seriously focus attention on the emerging field of medical geochemistry with the collaboration of geochemists and epidemiologists.

Dissanayake, C. B.; Chandrajith, Rohana

1999-10-01

350

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

351

Trace Element Geochemistry of New Nakhlites from the Antarctic and the Saharan Desert: Further Constraints on Nakhlite Petrogenesis on Mars  

Microsoft Academic Search

Ion microprobe measurements of REE and other selected trace and minor elements are reported in minerals of the new Antarctic (Y000593\\/749) and Saharan (NWA 998) nakhlites. Implications for their petrogenesis on Mars are discussed based on these geochemical data.

M. Wadhwa; G. Crozaz

2003-01-01

352

Distribution coefficients of 60 elements on TODGA resin: application to Ca, Lu, Hf, U and Th isotope geochemistry.  

PubMed

Batch equilibration experiments are conducted to measure the distribution coefficients (K(d)) of a large number of elements in nitric, nitric plus hydrofluoric, and hydrochloric acids on Eichrom TODGA extraction chromatography resin. The K(d)s are used to devise a multi-element extraction scheme for high-precision elemental and isotopic analyses of Ca, Hf, Lu, Th and U in geological materials, using high-purity lithium metaborate (LiBO(2)) flux fusion that allows rapid digestion of even the most refractory materials. The fusion melt, dissolved in nitric acid, is directly loaded to a TODGA cartridge on a vacuum chamber for elemental separation. An Ln-Spec cartridge is used in tandem with TODGA for Lu purification. The entire procedure, from flux digestion to preparation for isotopic analysis, can be completed in a day. The accuracy of the proposed technique is tested by measuring the concentrations of Ca (standard bracketing), Hf, Lu, Th and U (isotope dilution), and the isotopic composition of Hf in geostandards (USNM3529, BCR-2, BHVO-1, AGV-1 and AGV-2). All measurements are in excellent agreement with recommended literature values, demonstrating the effectiveness of the proposed analytical procedure and the versatility of TODGA resin. PMID:20298848

Pourmand, Ali; Dauphas, Nicolas

2010-01-22

353

Speciation of adsorbed yttrium and rare earth elements on oxide surfaces  

NASA Astrophysics Data System (ADS)

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

Piasecki, Wojciech; Sverjensky, Dimitri A.

2008-08-01

354

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

NASA Astrophysics Data System (ADS)

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

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

1997-09-01

355

Earth  

NSDL National Science Digital Library

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

356

Laser-ablation microprobe (LAM)-ICPMS unravels the highly siderophile element geochemistry of the oceanic mantle  

NASA Astrophysics Data System (ADS)

The highly siderophile element (HSE) contents of base-metal sulphides have been determined by laser-ablation microprobe (LAM)-ICPMS in abyssal peridotites from the Mid-Atlantic and South West Indian ridges. (Pd/Ir) N (0.007-505, N: CI-chondrite-normalised), (Pt/Ir) N (0.001-0.77) and (Rh/Ir) N (0.159-273) vary significantly between both grains and samples, irrespective of indicators of melt removal, but in line with bulk-rock platinum-group element (PGE) ratios and sulphide modal abundances. Positive deviations of PGE abundance ratios in whole-rock analyses are due to late-precipitated Cu-Ni-rich magmatic sulphides from incompletely extracted partial melts. These results contradict explanations of the HSE systematics of the oceanic mantle as reflecting global scale processes such as core-mantle exchange.

Luguet, A.; Alard, O.; Lorand, J. P.; Pearson, N. J.; Ryan, C.; O'Reilly, S. Y.

2001-07-01

357

Geochemistry of Eclogites and Metapelites from Trescolmen, Central Alps, as Observed from Major and Trace Elements and Oxygen Isotopes  

Microsoft Academic Search

Eclogites are often the only tangible high-pressure evidence we have from a paleosubduction zone, and they potentially preserve important geochemical information from the descending slab. Selected Group B\\/C eclogites and metapelites from the Trescolmen locality in the Adula nappe in the central Swiss Alps were chosen for a detailed investigation to determine oxygen isotope ratios and major- and trace-element compositions

Rene A. Wiesli; Lawrence A. Taylor; John W. Valley; Volkmar Tromsdorff; Masaki Kurosawa

2001-01-01

358

Major and trace element geochemistry in Zeekoevlei, South Africa: A lacustrine record of present and past processes  

Microsoft Academic Search

This study reports a multi-parameter geochemical investigation in water and sediments of a shallow hyper-eutrophic urban freshwater coastal lake, Zeekoevlei, in South Africa. Zeekoevlei receives a greater fraction of dissolved major and trace elements from natural sources (e.g., chemical weathering and sea salt). Fertilizers, agricultural wastes, raw sewage effluents and road runoff in contrast, constitute the predominant anthropogenic sources, which

Supriyo Kumar Das; Joyanto Routh; Alakendra N. Roychoudhury; J. Val Klump

2008-01-01

359

Geochemistry of the Merensky reef, Rustenburg Section, Bushveld Complex: controls on the silicate framework and distribution of trace elements  

Microsoft Academic Search

This whole rock and silicate mineral study focuses on the genesis of the Merensky reef sequence, as well as the footwall\\u000a and hanging wall norites at an area of Rustenburg Platinum Mines in a demonstrably normal (undisturbed) environment. Continuous\\u000a sampling provides major and trace element variations and mineral compositions and allows an evaluation of the post- liquidus\\u000a processes which affected

A. H. Wilson; C. A. Lee; R. T. Brown

1999-01-01

360

Constraints on mantle structure from geochemistry, seismology, and mixing studies: A numerical investigation of the compositional heterogeneity in the Earth's mantle  

NASA Astrophysics Data System (ADS)

Geochemical and seismological evidence indicate that the Earth's mantle is heterogeneous on all scales. Isotopic data indicate that the recycled components have a mean age of 1--2 Gyr, and that there may be a reservoir containing trace elements inferred to be missing from the shallow mantle. Constraints from argon and helium isotopes require that ˜50% of the Earth's mantle is outgassed, and that some OIBs have high 3He/4He. There is no consensus about the identification of this high helium ratio material, although the favorite explanation is primordial, undegassed material. Seismic tomography identifies the existence of long-wavelength strong heterogeneity at the base of the mantle and in the lithosphere. The existence of lateral heterogeneities requires that different isotopic domains be maintained for around 2 Gyr. To test whether a 2-D mantle convection model with self-consistent plate tectonics is able to reproduce the observed isotopic data, and to study how geochemical reservoirs evolve, suites of numerical experiments have been performed to investigate different aspects of the problem. The study focuses on the sensitivity of the results to uncertain physical properties, such as the density of subducted oceanic crust in the deepest mantle, and elemental partition coefficients. The main findings of the thesis are as follows (the caveat is that these need to be verified using 3D calculations): (1) The system self-consistently evolves the observed range of 3He/ 4He, but the exact distribution of ratios depends strongly on physical parameters and sampling method. Some parameter combinations simultaneously lead to MORB-like distributions of 3He/4He ratios in erupted material, and ˜50% outgassing of radiogenic 40Ar, consistent with geochemical constraints. (2) The system self-consistently evolves regions of HIMU (high 238U/204Pb) and low 143Nd/144Nd by segregation of subducted crust at the core-mantle boundary (CMB). The Pb-Pb age is about 2 Gyr. The effect of large strain on erasing heterogeneities must be included in the model, otherwise old material may have a strong effect on the age distribution, and the mean age of mantle heterogeneity. Moreover, the HIMU reservoir obtained in the model may provide a storage for some of the "missing" heat-producing elements. (3) Oceanic crustal differentiation and segregation cause strong seismic heterogeneity. When the crust is dense at the CMB, the model reproduces long-wavelength (L = 2) heterogeneity in the lower mantle. The presence of oceanic crust in the model contributes to the heterogeneity in the lithosphere. (4) Plate tectonics and variable viscosity have a strong effect on the lateral mixing behavior. Although chaotic mixing is typically observed in the study, horizontal heterogeneities may persist for more than 2 Gyr. Lateral mixing efficiency is controlled by strain rate and convective vigor.

Xie, Shunxing

361

Geochemistry and trace element behaviors of eclogite during its exhumation in the Xitieshan terrane, North Qaidam UHP belt, NW China  

NASA Astrophysics Data System (ADS)

The Xitieshan terrane, located in the central part of the North Qaidam ultrahigh pressure (UHP) metamorphic belt, China, is mainly composed of orthogneiss and paragneiss and a few intercalated eclogite layers and boudins. Based on their bulk-rock TiO2-contents, the eclogites can be subdivided into a high-Ti group (TiO2 > 2%) and a low-Ti group (TiO2 < 2%). Whole-rock major and trace element analyses revealed that the protoliths of the low-Ti eclogites are normal-type mid-ocean ridge basalts (N-MORB), whereas those of the high-Ti eclogites are either enriched-type mid-ocean ridge basalts (E-MORB) or near ridge seamount basalts, respectively. The Sr-Nd isotopes of eclogites of both groups are similar to those of MORB. Those of the low-Ti eclogites are characterized by positive \\z.epsivNd(T) and restricted ISr values and therefore provide further evidence for the formation of the protoliths of the eclogites in an oceanic environment. On the other hand, the Sr-Nd isotopes of high-Ti eclogites show mainly positive but also some negative \\z.epsivNd(T) values and relatively broadly distributed ISr values, indicating minor crustal contamination of the ocean floor basalts. Considering available 750-877 Ma protolith ages preserved in zircon cores, it is inferred that some of the eclogites derived from Neoproterozoic protoliths were emplaced onto the crust far ahead of the Paleozoic deep subduction, while the other eclogites originate from a different oceanic crust, e.g., the Paleo-Qilian ocean, indicating multiple orogenies in the geological history of the Xitieshan terrane, China.Whole-rock and in-situ LA-ICP-MS mineral trace element analyses of eclogites revealed two stages of fluid behavior during retrogression that correspond to the two exhumation stages uncovered by phase equilibrium calculations. The mineral scale trace element distributions and trace element inheritance of newly formed amphibole from its precursors indicate that, at the peak metamorphic stage (M1) and at the earlier (eclogite facies) overprint (M2), the fluid was internally controlled by the rock itself. Within a mafic lens, the amount of water-soluble elements (e.g., Rb, Sr, Ba, U, Pb and LREE), observed in the whole-rock compositions as well as in amphiboles, increases from the core (phengite-bearing eclogite) to the rim (amphibolite) and implies an external fluid source for the amphibolite facies retrogression (M3) which should be helpful for the final exhumation of UHP eclogite.

Zhang, Cong; Zhang, Lifei; Bader, Thomas; Song, Shuguang; Lou, Yuxing

2013-02-01

362

Consistent patterns of rare earth element distribution in accessory minerals from rocks of mafic-ultramafic complexes  

NASA Astrophysics Data System (ADS)

This paper summarizes analytical data accumulated in the world literature and other materials about the regularities of the REE distribution in minerals contained in ultramafic and mafic rocks as accessory phases. These minerals are tentatively divided into two groups. The first includes garnets, zircons, apatites and perovskites, which can accumulate increased amounts of REE in their structure. The second consists of minerals whose structure can accumulate only limited contents of these trace elements. These are chrome-spinels, ilmenites, and micas. These minerals, in respect of REE geochemistry, are studied to a varying degree because of the different levels of accumulations of these elements, different degrees of occurrence in rocks, tiny sizes of their grains and other reasons. The analytical database formed on their basis includes about 600 original analyses. The overwhelming majority of presently available data on REE geochemistry in accessory minerals from ultramafic and mafic rocks have been published only in the recent 15 years. The studies became possible due to the development and introduction of new highly sensible microprobe analyses allowing detection of REE and many other trace elements in minerals grains directly in thin sections. The greatest numbers of these analyses were performed for garnets and zircons, fewer for apatites, and the fewest for chrome-spinels, ilmenites, micas, and perovskites. In general, the regularities of REE distribution in these minerals from ultramafic and mafic rocks are less studied compared to the rock-forming minerals from ultramafic and mafic rocks. Among the analytical methods, which were used to study the REE composition of accessory minerals, the most efficient was the mass-spectrometry with inductively coupled plasma (ICP-MS).

Lesnov, Felix Petrovich

2013-03-01

363

Petrology and geochemistry of prograde deserpentinized peridotites from Happo-O'ne, Japan: Evidence of element mobility during deserpentinization  

NASA Astrophysics Data System (ADS)

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 Al2O3 (<1.0 wt.%), Cr2O3 (<0.35 wt.%), and Na2O (<0.6 wt.%) but high in Mg# (up to 0.98) and SiO2 (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 elements (e.g., Cs, Th, U, Ta) relative to their protoliths because of an external-element 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-element depletion in this tremolite is inherited from its source (antigorite + secondary diopside), whereas the depletion of mobile elements (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 elements 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-element contents than the retrograde one due to the external addition of these elements; it is enriched in B, Co and Ni, but depleted in Li that was liberated during deserpentinization by prograde metamorphism.

Khedr, Mohamed Zaki; Arai, Shoji

2012-01-01

364

Pb and Nd Isotope Variations and Elemental Geochemistry in Hydrothermal Sediments in a Push Core from Lucky Strike, 37ºN Mid-Atlantic Ridge  

NASA Astrophysics Data System (ADS)

We present a geochemical investigation of a near-vent hydrothermal metalliferous sediment core from the Lucky Strike (LS) hydrothermal field. LS is a high temperature neovolcanic hydrothermal field (fluids up to 325°C) in the Mid-Atlantic Ridge (MAR) at 37°N. The core was collected during the Seahma cruise (2001; FCT,. Portugal; FJAS Barriga, chief scientist; Ifremer's Atalante and ROV Victor). The sediment collected in the 22cm core consists of two main, slightly different varieties, both composed almost exclusively of hydrothermal minerals, mainly sphalerite, chalcopyrite, pyrite and barite, revealing negligible detrital and biogenic inputs. The deeper layers (>18cm) depict slight oxidation and contain fragments of altered basalt. The core reveals high concentrations of hydrothermally derived elements (e.g. Fe, Cu, Zn, Pb, Ba, Si) and low seawater and detrital input (e.g. U, Mg, Mn, Ca). Cu, Zn, Fe and Pb are mainly incorporated in sulphide phases. Chemical compositions evidence some seawater interaction towards the base of the core, with seawater input expressed in higher abundances of elements such as Mg, V, U and total rare earth elements (REE) and contributing for oxidation of sulfide minerals. The Al and Ca concentrations increase with core depth, suggesting a more pronounced detrital input and/or slightly more pronounced alteration in deeper levels. Rare earth element concentrations are low and REE (chondrite normalized) patterns are characteristic of vent fluids, with enrichment in light rare earth elements (LREE) and a pronounced positive Eu anomaly. Sediments from the upper levels of the core (<18cm) show a more hydrothermal REE profile than deeper ones. These patterns suggest that REE have been deposited from vent fluids with no interaction with unmodified seawater. At deeper layers, the REE concentrations reflect some seawater input and/or more extensive alteration. Lead isotopic ratios from this metalliferous sediment are identical to those of local basalts and are remarkably non- radiogenic when compared to pelagic sediments, revealing their hydrothermal origin. Lead has been removed from basalts by hot fluids and incorporated into LS metalliferous sediments. However, the 207Pb/204Pb and ^{143}Nd/^{144}Nd ratios reveal a small pelagic/seawater Pb and Nd contribution. These results show that minerals found in the LS sediment core have been precipitated directly from hydrothermal fluids circulating through the underlying rocks. No extensive seawater-sediment reactions have occurred in most of the core. However, data suggest a more significant seawater input and/or a larger sedimentary contribution in deeper layers. This could be explained by variable activity of the hydrothermal system during precipitation of the sediment, suggesting different pulses of activity of the LS hydrothermal system.

Barriga, F. J.; Dias, A.; Mills, R. A.; Taylor, R. N.; Ferreira, P.

2006-12-01

365

Continentally-derived solutes in shallow Archean seawater: Rare earth element and Nd isotope evidence in iron formation from the 2.9 Ga Pongola Supergroup, South Africa  

NASA Astrophysics Data System (ADS)

The chemical composition of surface water in the photic zone of the Precambrian ocean is almost exclusively known from studies of stromatolitic carbonates, while banded iron formations (IFs) have provided information on the composition of deeper waters. Here we discuss the trace element and Nd isotope geochemistry of very shallow-water IF from the Pongola Supergroup, South Africa, to gain a better understanding of solute sources to Mesoarchean shallow coastal seawater. The Pongola Supergroup formed on the stable margin of the Kaapvaal craton ˜2.9 Ga ago and contains banded iron formations (IFs) that represent the oldest documented Superior-type iron formations. The IFs are near-shore, pure chemical sediments, and shale-normalized rare earth and yttrium distributions (REY SN) exhibit positive La SN, Gd SN, and Y SN anomalies, which are typical features of marine waters throughout the Archean and Proterozoic. The marine origin of these samples is further supported by super-chondritic Y/Ho ratios (average Y/Ho = 42). Relative to older Isua IFs (3.7 Ga) from Greenland, and younger Kuruman IFs (2.5 Ga) also from South Africa, the Pongola IFs are depleted in heavy rare earth elements (HREE), and appear to record variations in solute fluxes related to sea level rise and fall. Sm-Nd isotopes were used to identify potential sediment and solute sources within pongola shales and IFs. The ?Nd( t) for Pongola shales ranges from -2.7 to -4.2, and ?Nd( t) values for the coeval iron-formation samples (range -1.9 to -4.3) are generally indistinguishable from those of the shales, although two IF samples display ?Nd( t) as low as -8.1 and -10.9. The similarity in Nd isotope signatures between the shale and iron-formation suggests that mantle-derived REY were not a significant Nd source within the Pongola depositional environment, though the presence of positive Eu anomalies in the IF samples indicates that high- T hydrothermal input did contribute to their REY signature. Isotopic mass balance calculations indicate that most (?72%) of the Nd in these seawater precipitates was derived from continental sources. If previous models of Fe-Nd distributions in Archean IFs are applied, then the Pongola IFs suggest that continental fluxes of Fe to Archean seawater were significantly greater than are generally considered.

Alexander, Brian W.; Bau, Michael; Andersson, Per; Dulski, Peter

2008-01-01

366

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

Microsoft Academic Search

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

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

1992-01-01

367

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

Microsoft Academic Search

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

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

1995-01-01

368

Mineralogy and geochemistry of platinum-group elements in the Aguablanca Ni-Cu deposit (SW Spain)  

NASA Astrophysics Data System (ADS)

The Aguablanca Ni-Cu-(PGE) magmatic sulphide deposit is associated with a magmatic breccia located in the northern part of the Aguablanca gabbro (SW, Iberia). Three types of ores are present: semi-massive, disseminated, and chalcopyrite-rich veined ore. The principal ore minerals are pyrrhotite, pentlandite and chalcopyrite. A relatively abundant platinum-group mineral (PGM) assemblage is present and includes merenskyite, melonite, michenerite, moncheite and sperrylite. Moreover, concentrations of base and precious metals and micro-PIXE analyses were obtained for the three ore-types. The mineralogy and the mantle-normalised chalcophile element profiles strongly suggest that semi-massive ore represents mss crystallisation, whereas the disseminated ore represents an unfractionated sulphide liquid and the chalcopyrite-rich veined ore a Cu-rich sulphide liquid. Palladium-bearing minerals occur commonly enclosed within sulphides, indicating a magmatic origin rather than hydrothermal. The occurrences and the composition of these minerals suggest that Pd was initially dissolved in the sulphides and subsequently exsolved at low temperatures to form bismutotellurides. Negative Pt and Au anomalies in the mantle-normalised chalcophile element profiles, a lack of Cu-S correlation and textural observations (such as sperrylite losing its euhedral shape when in contact with altered minerals) suggest partial remobilisation of Pt, Au and Cu by postmagmatic hydrothermal fluids after the sulphide crystallisation.

Piña, R.; Gervilla, F.; Ortega, L.; Lunar, R.

2008-01-01

369

Geochemistry of serpentinized peridotites from the Mariana Forearc Conical Seamount, ODP Leg 125: Implications for the elemental recycling at subduction zones  

NASA Astrophysics Data System (ADS)

Recent examinations of the chemical fluxes through convergent plate margins suggest the existence of significant mass imbalances for many key species: only 20-30% of the to-the-trench inventory of large-ion lithophile elements (LILE) can be accounted for by the magmatic outputs of volcanic arcs. Active serpentinite mud volcanism in the shallow forearc region of the Mariana convergent margin presents a unique opportunity to study a new outflux: the products of shallow-level exchanges between the upper mantle and slab-derived fluids. ODP Leg 125 recovered serpentinized harzburgites and dunites from three sites on the crests and flanks of the active Conical Seamount. These serpentinites have U-shaped rare earth element (REE) patterns, resembling those of boninites. U, Th, and the high field strength elements (HFSE) are highly depleted and vary in concentration by up to 2 orders of magnitude. The low U contents and positive Eu anomalies indicate that fluids from the subducting Pacific slab were probably reducing in nature. On the basis of substantial enrichments of fluid-mobile elements in serpentinized peridotites, we calculated very large slab inventory depletions of B (79%), Cs (32%), Li (18%), As (17%), and Sb (12%). Such highly enriched serpentinized peridotites dragged down to depths of arc magma generation may represent an unexplored reservoir that could help balance the input-output deficit of these elements as observed by Plank and Langmuir (1993, 1998) and others. Surprisingly, many species thought to be mobile in fluids, such as U, Ba, Rb, and to a lesser extent Sr and Pb, are not enriched in the rocks relative to the depleted mantle peridotites, and we estimate that only 1-2% of these elements leave the subducting slabs at depths of 10 to 40 km. Enrichments of these elements in volcanic front and behind-the-front arc lavas point to changes in slab fluid composition at greater depths.

Savov, Ivan P.; Ryan, Jeffrey G.; D'Antonio, Massimo; Kelley, Katherine; Mattie, Patrick

2005-04-01

370

Major, trace element and isotope geochemistry (Sr-Nd-Pb) of interplinian magmas from Mt. Somma-Vesuvius (Southern Italy)  

USGS Publications Warehouse

Major, trace element 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 element 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 elements (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-element 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 element 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.

Somma, R.; Ayuso, R. A.; De Vivo, B.; Rolandi, G.

2001-01-01

371

Evolution and timing of tectonic events in the Arabia-Eurasia convergence zone as inferred from igneous geochemistry from the EarthChem database  

NASA Astrophysics Data System (ADS)

The timing of tectonic events in the Anatolia-Iranian region can be inferred from analysis of igneous rocks. Magmatic activities in the region are generally associated with the convergence of the African-Arabian and Eurasian plates and the subduction of the Neotethys Ocean. Ancillary processes such as subduction of continental crust, delamination of upper plate lithosphere or lower crust, or asthenospheric decompression accompanying post-collisional relaxation also contribute to the composition of igneous rocks. Here we use geochemical data gathered from the EarthChem database to assess broad chemical implications of Cenozoic tectonic activities of the convergence region. We search for geochemical signal of the timing of first contact of the subducting Arabian and overriding Eurasian continental crust. Of particular interest is how igneous rock compositions vary during the transition from pre- to post-contact of the continental crusts. Also, is there a geographic variation along the convergence zone during this tectonic transition? We generate maps and geochemical plots for four different epochs and two different regions since Cenozoic time: Iran and Anatolia in the Eocene, Oligocene, Miocene and Plio-Quaternary. This board, region-scaled analysis of major and trace element patterns suggests the following tectonic events: Subduction-related medium K calc-alkaline igneous rocks reflect Eocene subduction of the Neo-Tethys oceanic lithosphere. Oligocene igneous rocks are characterized by K2O-SiO2 trends scattering to higher silica and alkaline content, which may reflect subduction of stretched continental margin lithosphere and sediments. A bimodal pattern of potash-silica trends during Miocene time may mark the transition from subduction-related to intra-plate magmatism, perhaps signaling contact between the continental crust of Arabia-Africa with Eurasia. Pliocene and younger igneous rocks show an intra-plate and ocean island basalt trend, as the region's activities transition to orogenic magmatism. Warren K Lieu and Robert J Stern The University of Texas at Dallas

Lieu, W. K.; Stern, R. J.

2011-12-01

372

Comments on "Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints" by Nikola Koglin, Dimitrios Kostopoulos and Thomas Reischmann, Tectonophysics 473 (2009), 53-68  

NASA Astrophysics Data System (ADS)

The manuscript "Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints" presented by Koglin et al. (2009a) tries to re-interpret the Samothraki ophiolite as a non ophiolitic mafic suite, which has been generated in a propagated fore-arc rift setting. However, incomplete sampling by the authors and overinterpretation of the few data are suspicious. The geochemical and petrological similarity of the Samothraki mafic sequence with other well-known ophiolites is not acknowledged and the proposed geotectonic regime is unrealistic.

Tsikouras, Basilios; Hatzipanagiotou, Konstantin

2010-03-01

373

Trace element geochemistry of volcanic gases and particles from 1983--1984 eruptive episodes of Kilauea volcano  

SciTech Connect

Compositional data have been obtained for volcanic gases and particles collected from fume emitted at the Pu'u O'o vent on the east rift zone of Kilauea volcano. The samples were collected by pumping fume through a filter pack system consisting of a front stage particulate filter followed by four base-treated filters (/sup 7/LiOH). Particles and condensed phases are trapped on the particulate filter, and acidic gases are collected on the treated filters. The filters are analyzed for 30 elements by instrumental neutron activation analysis. Fume samples were collected from the Pu'u O'o vent for two eruptive episodes: (1) 7 days after episode 11 (cooling vent samples) and (2) the stage of episode 13 (active vent samples).

Crowe, B.M.; Finnegan, D.L.; Zoller, W.H.; Boynton, W.V.

1987-12-10

374

Major and minor element geochemistry of deep-sea sediments in the Azores Platform and southern seamount region.  

PubMed

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 elements 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

Palma, Carla; Oliveira, Anabela; Valença, Manuela; Cascalho, João; Pereira, Eduarda; Lillebø, Ana I; Duarte, Armando C; Pinto de Abreu, Manuel

2013-07-26

375

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

PubMed

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

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

2013-07-03

376

Rare earth elements in Ca-phosphates of Allende carbonaceous chondrite  

SciTech Connect

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

Ebihara, M.; Honda, M.

1987-09-01

377

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

NASA Astrophysics Data System (ADS)

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

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

1993-12-01

378

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

SciTech Connect

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

Scott A. Wood

2002-01-28

379

Thermochemical treatment of zeolitic cracking catalysts containing rare-earth elements  

SciTech Connect

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

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

1987-01-01

380

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

PubMed

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

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

2010-10-19

381

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

SciTech Connect

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

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

1988-08-01

382

Using mineral trace element geochemistry to track magma processes in a "big tank" magma chamber: a laser ablation ICP-MS study of hornblende and augite  

NASA Astrophysics Data System (ADS)

Processes in magma chambers have been the subject of many discussions. Incremental emplacement models, supported by U-Pb zircon geochronology, preclude mixing, fractional crystallization and assimilation as chamber-wide processes. However, low-velocity seismic anomalies interpreted as partially molten areas in the crust, voluminous dacitic ignimbrites, and field evidence for crystal accumulation argue for large volumes of crystal-rich mush in the crust. In this study we use the trace element composition of liquidus phases augite and hornblende in the Wooley Creek batholith (WCb), Klamath Mountains, northern California, to reconstruct the geochemical history of the batholith. The WCb is a tilted pluton emplaced between 160 and 155 Ma. The lower WCb ranges from 2-pyroxene gabbro to hornblende tonalite. Variations in the texture and the proportions of hornblende and pyroxene suggest that the lower part was emplaced as several magma batches that reached hornblende stability at different temperatures and times. Augite crystals are normally zoned, with variable Cr (200-3000 ppm) and Ti (1000-4000 ppm) concentrations. Eu anomalies get progressively larger toward the rims, suggesting an evolution of individual melt batches by simple fractional crystallization. The central part of the pluton is mainly hornblende biotite quartz-diorite. Mafic enclaves and syn-plutonic dikes are abundant. Pyroxenes is rarely preserved in that part of the pluton. The upper WCb ranges from hornblende biotite quartz diorite to hornblende biotite granite. Bulk rock major element geochemical trends are consistent with upward differentiation of a single, unified magma batch. This interpretation is supported by homogenous trace element compositions of hornblende throughout the upper part of the pluton. Dacitic roof dikes contain hornblende phenocrysts identical to those in the upper WCb, indicating that the mush present in the upper WCb was eruptible. Two-pyroxene andesitic roof dikes are common and were interpreted as originating from the lower WCb. Oscillatory trace element zoning of augite plus low Cr (<1000 ppm) and high Ti (>3000 ppm) concentrations suggest that the dikes were derived from the central WCb, where evidence of replenishment and mingling is widespread. Thus, the lower and central parts of the pluton were emplaced as multiple, distinct magma batches. In contrast, the upper part of the pluton can be explained as (1)several batches of internally homogeneous magma emplaced at different times, with successively more evolved magma emplaced toward the top, or (2) evolution from a single large magma volume ('big tank') that could have been emplaced incrementally or as one batch. Existence of an upper 'big tank' is consistent with the lack of internal contacts, the presence of coherent geochemical trends and the presence of dacitic roof dikes compositionally identical to the upper part of the WCb. This study shows that mineral trace element geochemistry is a powerful tool in deciphering the size and evolution of magma batches within crystallized plutons.

Coint, N.; Barnes, C. G.; Barnes, M. A.; Yoshinobu, A. S.

2011-12-01

383

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

Microsoft Academic Search

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

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

2011-01-01

384

Basalts of the northeastern Deccan Traps, India: Isotopic and elemental geochemistry and relation to southwestern Deccan stratigraphy  

NASA Astrophysics Data System (ADS)

The northeastern Deccan Traps include flows with strong isotopic and elemental affinities to lavas in the southwest as far as 900 km away. However, many of the northeastern flows show a negative correlation of 206Pb/204Pb with ?Nd(t) and positive correlation of 206Pb/204Pb with (87Sr/86Sr)t, distinct from any of the isotopic fields for the southwestern formations; this array (from ?Nd(t)=+5, (87Sr/86Sr)t=0.7041, 206Pb/204Pb=17.9 to ?Nd(t)=0, (87Sr/86Sr),=0.7068, 206Pb/204Pb=20.5) overlaps the Ambenali Formation (Fm.) field and runs toward that of the "common signature" [Peng et al., 1994] that appears to have been an important magma type in several of the lower formations of the southwest. This array appears to represent mixing between an Ambenali-type and (1) a common-signature end-member or (2) an end-member with even higher 206Pb/204Pb and 87Sr/86Sr and lower ?Nd than the common signature; such mixing has been postulated, but not documented previously, for the Deccan. Lavas isotopically and chemically indistinguishable from the Ambenali Fm. form the tops of sections near Jabalpur and Chikaldara. Beneath them are flows that chemically resemble the Poladpur Fm. (which sits immediately below the Ambenali in the southwest) and several lavas similar to the Khandala Fm. (beneath the Poladpur and intervening Bushe Fm. in the southwest). Given the general stratigraphic correspondence with the southwestern sequence, many of these northeastern flows may be petrogenetically related to the respective southwestern formations. Lavas with broadly Poladpurand Khandala-like elemental compositions are also abundant in a thick section south of Mhow; several other Mhow-area flows resemble the distinctive Bushe Fm. However, nearly all of the Poladpur- and Khandala-like northeastern Deccan lavas analyzed have higher 206Pb/204Pb man any southwestern Poladpur or Khandala Fm. basalts. If they indeed are related petrogenetically to these formations, many of the northeastern magmas interacted less with lOw-206Pb/204Pb continental material and thus must have erupted from different feeder systems.

Peng, Z. X.; Mahoney, J. J.; Hooper, P. R.; MacDougall, J. D.; Krishnamurthy, P.

1998-12-01

385

The effect of mining and related activities on the sediment trace element geochemistry of the Spokane River Basin, Washington, USA  

USGS Publications Warehouse

Surface sediments in the Spokane River Basin are enriched in Pb, Zn, As, Cd, Sb, and Hg relative to local background levels. Maximum enrichment occurs in the Upper Spokane River in close proximity to Lake Coeur d'Alene. On average, enrichment decreases downstream. Subsurface sediments also are enriched in Pb, Zn, As, Cd, Sb, and Hg relative to background levels. Enrichment began between 1900 and 1920 in the middle of the basin; this is contemporaneous with similar findings in Lake Coeur d'Alene (the upstream source of the Spokane River), as well as the completion of Long Lake Dam (1913). In the most downstream part of the basin, enrichment began between 1930 and 1940. This temporal shift may reflect the latter's greater distance from the Coeur d'Alene River Basin, the presumptive source of the enriched trace elements, but is more likely the result of the completion of Grand Coulee Dam (1934-1941) which backed up the Spokane River, and elevated water levels by about 30 m in the most downstream part of the basin.

Grosbois, C. A.; Horowitz, A. J.; Smith, J. J.; Elrick, K. A.

2002-01-01

386

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

387

Trace element geochemistry of the 1991 Mt. Pinatubo silicic melts, Philippines: Implications for ore-forming potential of adakitic magmatism  

NASA Astrophysics Data System (ADS)

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 elements 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.

Borisova, Anastassia Yu.; Pichavant, Michel; Polvé, Mireille; Wiedenbeck, Michael; Freydier, Remi; Candaudap, Frédéric

2006-07-01

388

Metasomatic- hydrothermal processes in the Qatruyeh area, Iran: Mineralogy and trace elements geochemistry of metasedimentary rock- hosted iron indices  

NASA Astrophysics Data System (ADS)

The Qatruyeh iron indices are located at about 40 Km northeast of Neyriz, in the eastern edge of the HP-LT Sanandaj-Sirjan metamorphic belt, Zagros Mountain. Qatruyeh indices are contained within the metasedimentary rocks of the Late Proterozoic- early Paleozoic, which consists predominantly of dolomitic limestone, greenschist and quartzite. Field investigations, mineralogical studies and XRD analyses indicate that orebodies are dominated by magnetite. The structures of orebodies are mainly formed as thin layers and massive, which are located between dolomitic limestones and greenschists. Tourmaline, muscovite, chlorite, talc, martite, specularite, goethite, limonite, pyrite and chalcopyrite are present as minor minerals. The area has experienced two different stages of metasomatic- hydrothermal alterations. The iron ores were formed during the metasomatic- hydrothermal processes. Those processes are: (1) Na-Ca alteration and (2) mineralization (Oxidation-Sulfidation). The first stage of alteration follows the attainment of peak regional metamorphic condition (187± 2.6 Ma based on zircon SHRIMP U- Pb). This alteration is accompanied with Low-grade magnetite ores formation (50 % Fe2O3t), replacement textures, gradual transformation between layered ores and host rock. Wet chemistry analyses on magnetite shows that Na-Ca alteration caused increasing Cr and Cu as transition metals and Ni, Co and V were depleted. Metasedimentary rock-hosted iron deposits indicate that Na-Ca alteration increase Cu, Ni, Cr, Co, Zn as immobile elements and Na-Fe, whereas the LILE (Pb, Sr) were depleted. The formation of paragonite-tourmaline is also occurs as a part of iron deposition process in the stage. The second stage of metasomatic- hydrothermal alteration is accompanied with widespread veins and veinlets of High-grade magnetite (75 % Fe2O3t) - hematite- Quartz. Mineralization took place along host rock fractures with passage of saline, hot and oxidized aqueous fluids. Paragonite altered to muscovite in the host-rocks and ores in the stage. Sulfide replacement is generally occurred as a late stage phase.

Rajabzadeh, M. A.; Asadi, S.

2009-04-01

389

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

PubMed

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

Zhang, Yigang; Yin, Qing-Zhu

2012-11-13

390

Isotopic geochemistry and cosmochemistry  

NASA Astrophysics Data System (ADS)

The book includes recent information on isotope geology, geochemistry, and cosmochemistry, discussed at a recent Soviet-Japanese symposium (at Irkutsk, USSR). Attention is given to numerical modeling of geochronometric systems, a classification of noble-gas components in the earth's interior, the feasibility of using ion microprobe for local isotope analysis of zircons for the purpose of deriving the early history of the earth (on the example of the Novopavlovsk complex from the Ukranian shield), a geological and geochronological study of the Ganalski complex of Kamchatka, and strontium isotopes as a criterion of the nature of acid melts (i.e., mantle- or crust-related). Other papers are on the geochronology and geology of Siberian kimberlites, the nature of sulfur from effusive rocks of the Kamchatka-Kuril-Japan island arc, mass-spectrometric studies of volatile components in exocontact rocks of alkaline-basic intrusions, and an analytical method for stable-isotope analysis in ultrasmall amounts of CO2 and its application to studies of the microscale isotopic zoning in calcite and graphite crystals in marble.

Shchukoliukov, Iu. A.

391

Thickening and propagation of the Pamir plateau: insights from monazite and titanite geochronology and trace-element geochemistry, eastern Tajikistan  

NASA Astrophysics Data System (ADS)

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 element 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.

Stearns, M. A.; Hacker, B. R.; Kylander-Clark, A. R.; Ratschbacher, L.; Seward, G.

2011-12-01

392

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

Microsoft Academic Search

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

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

1995-01-01

393

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

394

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

Microsoft Academic Search

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

TSUYOSHI ISHIKAWA; KENJI SUGIMOTO; KAZUYA NAGAISHI

395

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

Microsoft Academic Search

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

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

2002-01-01

396

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

Microsoft Academic Search

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

J. G. Crock; F. E. Lichte

1982-01-01

397

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

Microsoft Academic Search

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

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

2006-01-01

398

Physicochemical variations in atmospheric aerosols recorded at sea onboard the Atlantic-Mediterranean 2008 Scholar Ship cruise (Part II): Natural versus anthropogenic influences revealed by PM 10 trace element geochemistry  

NASA Astrophysics Data System (ADS)

The geochemistry of PM 10 filter samples collected at sea during the Scholar Ship Atlantic-Mediterranean 2008 research cruise reveals a constantly changing compositional mix of pollutants into the marine atmosphere. Source apportionment modelling using Positive Matrix Factorization identifies North African desert dust, sea spray, secondary inorganic aerosols, metalliferous carbon, and V-Ni-bearing combustion particles as the main PM 10 factors/sources. The least contaminated samples show an upper continental crust composition (UCC)-normalised geochemistry influenced by seawater chemistry, with marked depletions in Rb, Th and the lighter lanthanoid elements, whereas the arrival of desert dust intrusions imposes a more upper crustal signature enriched in "geological" elements such as Si, Al, Ti, Rb, Li and Sc. Superimposed on these natural background aerosol loadings are anthropogenic metal aerosols (e.g. Cu, Zn, Pb, V, and Mn) which allow identification of pollution sources such as fossil fuel combustion, biomass burning, metalliferous industries, and urban-industrial ports. A particularly sensitive tracer is La/Ce, which rises in response to contamination from coastal FCC oil refineries. The Scholar Ship database allows us to recognise seaborne pollution sourced from NW Africa, the Cape Verde and Canary islands, and European cities and industrial complexes, plumes which in extreme cases can produce a downwind deterioration in marine air quality comparable to that seen in many cities, and can persist hundreds of kilometres from land.

Moreno, Teresa; Pérez, Noemi; Querol, Xavier; Amato, Fulvio; Alastuey, Andrés; Bhatia, Ravinder; Spiro, Baruch; Hanvey, Melanie; Gibbons, Wes

2010-07-01

399

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

400

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

Microsoft Academic Search

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

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

1996-01-01

401

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

Microsoft Academic Search

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

Fuliang Li; Xiaoquan Shan; Tianhong Zhang; Shuzhen Zhang

1998-01-01

402

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

Microsoft Academic Search

Sorption of the 14 rare earth elements (REE) by basaltic rock is investigated as a function of pH, ionic strength and aqueous REE concentrations. The rock sample, originating from a terrestrial basalt flow (Rio Grande do Sul State, Brazil), is composed of plagioclase, pyroxene and cryptocrystalline phases. Small amounts of clay minerals are present, due to rock weathering. Batch sorption

E. Tertre; A. Hofmann; G. Berger

2008-01-01

403

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

National Technical Information Service (NTIS)

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

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

1998-01-01

404

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

Microsoft Academic Search

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

Yu-Ran Luo; Robert H. Byrne

2004-01-01

405

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

Microsoft Academic Search

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

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

1998-01-01

406

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

Microsoft Academic Search

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

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

2006-01-01

407

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

Microsoft Academic Search

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

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

2006-01-01

408

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

Microsoft Academic Search

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

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

1979-01-01

409

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

Microsoft Academic Search

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

Bruno Reynard; Christophe Lécuyer; Patricia Grandjean

1999-01-01

410

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

Microsoft Academic Search

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

John N. Ludden; Geoffrey Thompson

1979-01-01

411

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

Microsoft Academic Search

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

D. J. Piepgrass; S. B. Jacobsen

1992-01-01

412

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

Microsoft Academic Search

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

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

2006-01-01

413

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

Microsoft Academic Search

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

D. I. T. Fávaro; B. P. Mazzilli

2005-01-01

414

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

Microsoft Academic Search

This work analyses the spatial distribution, the origin, and the shale-normalised fractionation patterns of the rare earth elements (REE) in the alluvial aquifer of the Guadiamar River (south-western Spain). This river received notoriety in April 1998 for a spill that spread a great amount of slurry (mainly pyrites) and acid waters in a narrow strip along the river course. Groundwaters

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

2005-01-01

415

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

Microsoft Academic Search

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

Johan Ingri; Anders Widerlund

1994-01-01

416

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

Microsoft Academic Search

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

D. Merten; E. Kothe; G. Büchel

2004-01-01

417

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

Microsoft Academic Search

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

A. A. Pupyshev; E. V. Semenova

2000-01-01

418

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

Microsoft Academic Search

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

Nobuo Kamehara; Kazuaki Kwihara

2008-01-01

419

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

Microsoft Academic Search

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

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

1990-01-01

420

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

PubMed

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45?×?10(9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO(2)) by UV light with ??elemental sulfur (S(8)) and sulfuric acid (H(2)SO(4)) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO(2) either photolyzes at wavelengths from 115 to 400?nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H(2)) or methane (CH(4)), increased the formation of S(8). With UV photolysis, formation of S(8) aerosols is highly dependent on the initial SO(2) pressure; and S(8) is only formed at a 2% SO(2) mixing ratio and greater in the absence of a reductant, and at a 0.2% SO(2) mixing ratio and greater in the presence of 1000?ppmv CH(4). We also found that organosulfur compounds are formed from the photolysis of CH(4) and moderate amounts of SO(2). The implications for sulfur aerosols on early Earth are discussed. Key Words: S-MIF-Archean atmosphere-Early Earth-Sulfur aerosols. PMID:21087157

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

2010-10-01

421

The trace element geochemistry of clinopyroxenes from pyroxenites in the Lewisian of NW Scotland: insights into light rare earth element mobility during granulite facies metamorphism  

Microsoft Academic Search

Clinopyroxenes from layered pyroxenites and from pyroxenite pods in felsic gneisses of the Lewisian granulite complex, NW\\u000a Scotland, have distinctive chemistries suggestive of different origins. Clinopyroxenes in the layered pyroxenites crystallised\\u000a from mafic melts in a magma chamber located in the middle to shallow crust, whereas clinopyroxenes in pods in the felsic gneisses\\u000a crystallised from the tonalitic protolith to the

Hugh Rollinson; Philip Gravestock

422

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

PubMed

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

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

2003-06-01

423

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

NASA Astrophysics Data System (ADS)

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

Tang, Jianwu; Johannesson, Karen H.

2010-12-01

424

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

Microsoft Academic Search

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

Peter Dulski

1994-01-01

425

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

426

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

SciTech Connect

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

Guo, Y.; Whitehead, M. A.

1989-07-01

427

The elemental, delta44Ca, and delta26Mg geochemistry of granite weathering at pH = 1 and T = 25°C  

Microsoft Academic Search

We conducted a plug flow reactor experiment at pH = 1 and T = 25°C using the 45-850 mum size fraction of crushed Boulder Creek Granodiorite. The goal of the study was to improve understanding of granite weathering and constrain its influence on the Ca and Mg isotope geochemistry of terrestrial waters. Ultrapure, 0.1 N HCl was introduced at a

J. Ryu; A. D. Jacobson; C. Holmden; C. Lundstrom; Z. Zhang

2009-01-01

428

Elemental and Nd–Sr–Pb isotope geochemistry of flows and dikes from the Tapi rift, Deccan flood basalt province, India  

Microsoft Academic Search

The Deccan Traps are a large rift-associated continental flood basalt province in India, parts of which have been studied extensively in terms of geochemistry, palaeomagnetism and stratigraphy. However, the basalts of the Tapi rift in the central part of the province have been little-studied thus far. Two ENE–WSW-trending tectonic inliers of the Deccan basalts in this region, forming ridges rising

D. Chandrasekharam; J. j. Mahoney; H. c. Sheth; R. a. Duncan

1999-01-01

429

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

NASA Astrophysics Data System (ADS)

Rare earth element (REE) and other selected trace and minor element concentrations were measured in individual grains of orthopyroxene, feldspathic glass (of plagioclase composition) and whitlockite of the ALH84001 martian meteorite. Unlike in other martian meteorites, phosphate is not the main REE carrier in ALH84001. The REE pattern of ALH84001 bulk rock is dependent on the modal abundances of three REE-bearing phases, i.e., orthopyroxene (which contains most of the HREEs), feldspathic glass (which dominates the Eu abundances) and whitlockite (which contains the majority of the LREEs). Variations in the REE abundances previously observed in different splits of ALH84001 can easily be explained in terms of small variations in the modal abundances of these three minerals, without the need to invoke extensive redistribution of LREEs. At least some orthopyroxenes (i.e., those away from contacts with feldspathic glass) in ALH84001 appear to have preserved their original REE zonation from igneous fractionation. Estimate of the ALH84001 parent magma composition from that of the unaltered orthopyroxene `core' (i.e., zoned orthopyroxene with the lowest REE abundances) indicates that it is LREE-depleted. This implies that the martian m