Heavy rare-earth elements

Heavy Rare Earth Element). Therefore, it is considered that negative Ce and positive Eu anomalies in hydrothermally altered volcanic rocks, Kuroko ores, and ferruginous chert and LREE enrichment in the Kuroko ores have been caused by hydrothermal alteration and precipitations of minerals from hydrothermal solution responsible for sulfides-sulfate (barite) mineralization. 

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. 

HELP HEU HFO HFR HLW HREE HRL HT HTGR HWR Hydrological evaluation of landfill performance Highly enriched uranium Hydrous ferrous oxide or ferric hydroxide Hot fractured-rock High-level nuclear waste Heavy rare earth elements (Gd-Lu) Hard rock laboratory High temperature High-temperature gas-cooled reactor Heavy water reactor... 

In the f -Pt-Sb systems, the compounds with Y3Au3Sb4 structure are found for both the light and heavy rare earth elements. This structure occurs typically for copper and gold containing antimonides, and unexpectedly, it was not observed for the systems with Ni and Pd. 

The lanthanide contraction is probably the reason why the natural processes lead to fractionation and give rise to cerium group elements containing mainly the larger rare earth elements of lower atomic numbers, and to yttrium earth minerals containing mainly smaller rare earth elements with higher atomic numbers. Yttrium, although not a rare earth element, its atomic number 39 is low and its radius is similar to that of Ho. Thus yttrium appears with heavy rare earth elements. 

Figure 12 Chemical and isotopic correlations among shergottites, arising from assimilation of a crustal component. Decreasing values of 5 " Nd indicate increasing assimilation. This parameter correlates with magma redox state, indicated by size of the Eu anomaly in pyroxenes (Wadhwa, 2001), and ratio of light-to-heavy rare-earth elements (after McSween, 2002).

The main target of Sm-Nd and Lu-Hf dating in metamorphic studies continues to be the mineral garnet. Garnet is a major constituent in many metamorphic rocks it preferentially incorporates heavy rare earth elements, and hence can have very high (e.g., Stosch andLugmarr, 1987)... 

Figure 2(C) is the result of a calculation that illustrates which cations might fit into sixfold coordination position in the calcite group structures. It is an interesting insight as both light and heavy rare earth elements are possible substitutes for calcium in the calcium carbonate structure, i.e., they plot within 15% of the calcium ionic size. However, some of the end-members incorporate elements into this crystal structure and are outside this deviation but within 30%, an expression of the potential physical expansion for this layered crystal structure. These are ionic charge differences important in whether a stable crystalline structure can be produced. Trace amounts of all these ions can be incorporated in calcite and may dictate the morphology of the crystallites. Therefore, the presence and amount of any ions in the environment in which carbonate crystallization occurs may possibly be recorded. However, in spite of the predominance of sodium and potassium in the solutions where...

Element 103 should complete the actinide series of heavy rare earth elements. It should be analogous in its chemical properties to the rare earth lutetium. 

TABLE 4-3. Overlap populations between 4f and 02p AO s ( X l(f, ealculated per ligand) in oxides of light rare-earth elements (Csv elusters with two types of ligands) and heavy rare-earth elements (ftd elusters and C2 clusters with three types of ligands.) (Reproduced with petmission from ref 8 and 9. 

Apatite from the Khibina alkahne complex is mainly fluorapatite Ca5(P04)F, with enrichment of light rare earth elements (La, Ce, Pr, Nd, Sm, Eu). The investigated LREE + Y contents range from 4268 to 4464 ppm (with an average of 656 ppm for Nd). The content of the more rare heavy rare earth elements (Gd, Dy, Er, Yb) is minor (HREE = 405 ppm). (Stoltz and Meyer 2012). 

As previously stated, the REEs are often divided into the light rare earth elements (LREEs) and the heavy rare earth elements (HREEs). This definition is based on the electron configuration of each rare earth element. The LREEs are defined as lanthanum, with atomic number 57 to gadolinium, wifli atomic number 64. The HREEs are defined as terbium with atomic number 65 to lutetium with atomic number 71, and also includes yttrium, with atomic number 39. The HREEs differ from the LREEs in that they have paired electrons (clockwise and... 

A chemical polish which can be used at room temperature consists of 25 ml dimethylformamide, 20 ml lactic acid, 5 ml phosphoric acid, 10 ml acetic, 15 ml nitric acid and 1 ml sulfuric acid (Koch and Picklesimer, 1967). The above solution is a dilution (with dimethylformamide) of Roman s solution (1966) which was developed for polishing the heavy rare earth elements. A modification of the... 

Cp Cyclopentadienyl HREE Heavy Rare Earth Elements... 

The range of formation of ternary R-Fe-Ge compounds is restricted to concentrations of less than 42 at.% rare-earth metal Rn7Fe52Gei]2 (Tbn7Fe52Gen2 type) is the terminal R-rich phase. Ternary compounds with light lanthanides are foimd predominantly in the range 40-70 at.% Ge, whereas the heavy rare-earth elements form compounds primarily in the concentration region from 28 to 50 at.% Ge. 

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