Light rare-earth elements

The REE pattern for fresh volcanic rocks in the Kuroko mine area studied by Dudas et al. (1983) is shown in Fig. 1.47 which shows no negative Ce and no positive Eu anomalies and FREE (Light Rare Earth Element) are not enriched compared with HREE... 

Elderfield and Greaves [629] have described a method for the mass spectromet-ric isotope dilution analysis of rare earth elements in seawater. In this method, the rare earth elements are concentrated from seawater by coprecipitation with ferric hydroxide and separated from other elements and into groups for analysis by anion exchange [630-635] using mixed solvents. Results for synthetic mixtures and standards show that the method is accurate and precise to 1% and blanks are low (e.g., 1() 12 moles La and 10 14 moles Eu). The method has been applied to the determination of nine rare earth elements in a variety of oceanographic samples. Results for North Atlantic Ocean water below the mixed layer are (in 10 12 mol/kg) 13.0 La, 16.8 Ce, 12.8 Nd, 2.67 Sm, 0.644 Eu, 3.41 Gd, 4.78 Dy, 407 Er, and 3.55 Yb, with enrichment of rare earth elements in deep ocean water by a factor of 2 for the light rare earth elements, and a factor of 1.3 for the heavy rare earth elements. 

Elution volume calibrations were performed using radioactive tracers of the rare earth elements and 133Ba, with atomic-absorption or flame-emission analysis of iron, sodium, potassium, calcium, and magnesium. As shown in Fig. 5.14, any barium added to the second columns is eluted at the start of the light rare earth element fraction . To ensure barium removal the sample can be put through the first column again. 

Linsalata P, Franca EP, Eisenbud M. 1985. Determination of the human intake of thorium and the light rare earth elements from high and typical natural radiation environments. Trace Subst Environ Health 19 257-263. 

Linsalata P, Penna Franca E, Sachett I, et al. 1987. Radium, thorium, and the light rare earth elements in soils and vegetables grown in an area of high natural radioactivity. DOE Symp Ser 59 131-146. 

LDH LEU LIBD LAW LET LILW LIP LLNL LLW LMA LMFBR LOI LREE L/S LTA LWR Layered double hydroxide Low enriched uranium Laser-induced breakdown detection Low-activity waste Linear energy transfer Low- and intermediate-level nuclear waste Lead-iron phosphate Lawrence Livermore National Laboratory Low-level nuclear waste Law of mass action Liquid-metal-cooled fast-breeder reactor Loss on ignition Light rare earth elements (La-Sm) Liquid-to-solid ratio (leachates) Low-temperature ashing Light water reactor... 

Borg L., Norman M., Nyquist L., Bogard D., Snyder G., Taylor L., and Lindstrom M. (1999) Isotopic studies of ferroan anorthosite 62236 a young lunar crustal rock from a light rare-earth-element-depleted source. Geochim. Cosmochim. Acta 63, 2679-2691. 

Hermann 1. (2002b) AUanite thorium and light rare earth element carrier in subducted crust. Ghent. Geol. 192, 289-306. 

Adakite This term is justly popular, but unfortunately it means many different things to different people, so we try not to use it. It generally is used for andesites and dacites with extreme light rare earth element (REE) enrichment (e.g., G2jYh > 9), very high Sr/Y ratios (e.g., Sr/Y > 50), and low yttrium and heavy REE concentrations (e.g., Y < 20 ppm, Yb < 2 ppm). 

The hydroxides of berklium(III), Bk(OH)3, and califomium(III), Cf(OH)s, behave in a similar fashion [3]. In their crystalline forms, Am(OH)s and Cm(OH)3 are anhydrous (as are hydroxides of light rare-earth elements), and are hexagonal, C 6h P s/m space group, a = 6.420 and 6.391 A, c = 3.745 and 3.712 A, for Am and Cm compounds, respectively. Due to self-irradiation, the unit-cell parameters increase with time, as does the sample amorphization. In the case of " Cm(OH)3, the stmcture decomposes within 1 day, but the same process for " Am(OH)3 takes up to 4-6 months [4]. The Mossbauer spectrum of Am(OH)3 [5] is characterized by 5 = 4.6 cm/c (relative to Am02). The nuclear magnetic resonance (NMR) studies indicate that, among the TUE(III) hydroxides, the Am compound has the most covalent chemical bonds. The TUE(III) hydroxides are readily soluble in different mineral acids under these conditions, the solutions of hydrated An ions are produced. 

In contrast, the steady increase in Nd values in the Earth s mantle with time after 3.0 Ga does have a geological meaning and implies the progressive extraction of the light rare Earth elements from the Earth s mantle. The most popular explanation of this fractionation... 

One difficulty is that there is no stable isotope of plutonium with which to compare its abundance. To really quantify its abundance, it is necessary to consider the amount of " " Pu relative to an isotope of a similar element. The definition of similar depends on the problem to be addressed. In studies of nucleosynthesis, the similar element used is usually uranium, another actinide, which is produced in the same stellar environments. In studies of the history of specific meteorite parent bodies, the similar element is more commonly a light rare earth element (TREE) like neodymium, since the geochemical behavior of plutonium is apparently most similar to that of the LREE. We will discuss the details of the experimental technique of each approach below. 

Linsalata P, Eisenbud M and Franca EP (1986) Ingestion estimates ofThand the light rare earth elements based on measurements of human feces. 

Natural monazite contains not only cations of the light rare-earth elements, but it also incorporates uranium and thorium. Monazite is the principal ore for the commercial extraction of thorium, and it has also been used as a secondary source of uranium. Monazite deposits are located in the United States, Australia, South Africa, Sri Lanka, Brazil, India, Malagasy, and Canada. As shown in Table 1, monazite is capable of incorporating significant amounts of both uranium and thorium (Boatner and Sales 1988, Houk 1943). Because of the chemical durability of monazite, relatively harsh chemical... 

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