Spinel rare earth elements

The summary of the bulk chemical compositions (major elements, minor elements, rare earth elements), Sr/ Sr (Farrell et al., 1978 Farrell and Holland, 1983), microscopic observation, and chemistry of spinel of unaltered basalt clarifies the tectonic setting of Kuroko deposits. Based on the geochemical data on the selected basalt samples which suffered very weak alteration, it can be pointed out that the basalt that erupted almost contemporaneously with the Kuroko mineralization was BABB (back-arc basin basalt) with geochemical features of which are intermediate between Island arc tholeiite and N-type MORE. This clearly supports the theory that Kuroko deposits formed at back-arc basin at middle Miocene age. 

Blundy JD, Wood BJ, Davies A (1996) Thermodynamics of rare earth element partitioning between clinopyroxene and melt in the system Ca0-Mg0-Al203-Si02. Geochim Cosmochim Acta 60 359-364 Blundy JD, Robinson JAC, Wood BJ (1998) Heavy REE are compatible in clinopyroxene on the spinel Iherzolite solidus. Earth Planet Sci Lett 160 493-504... 

Probably the most informative objects in meteorites are the refractory, calcium-aluminum-rich inclusions (CAIs). They are sub-millimeter- to centimeter-sized objects found in all types of primitive (chondritic) meteorites. On the basis of their uranium/lead radiometric ages, they are believed to be the first-formed rocks in the Solar System 4). Their chemical compositions are consistent with equilibrium condensation as solids from a gas of solar composition at high temperatures 1700 K). The major mineral phases are spinel (MgAl204), pyroxene (Mg, Ca, Al, Ti silicate), melilite (another Mg, Ca, A1 silicate), and anorthite (CaAl2Si20s). They are enriched in refractory (less volatile) trace elements, such as the rare-earth elements, by a factor of 15-20 (5), reflecting their high temperature of condensation. The abundances of the three stable isotopes of oxygen exhibit a pattern not seen in any terrestrial rocks (6). On earth, ratios of abundances of isotopes, such as and vary by... 

McKenzie D, O Nions RK (1995) The source regions of ocean island basalts. J Petrol 36 133-159 Meen JK, Eggler DH, Ayers JC ((1989) Experimental evidence for very low solubility of rare earth elements in C02-rich fluids at mantle conditions. Nature 340 301-303 Menzies M, Chazot G (1995) Fluid processes in diamond to spinel facies shallow mantle. J Geodynamics 20 387-415... 

The most often found types of mixed oxides are perovskites (RBO3), K2NiF4-type oxides (R2BO4), R 1 B C>2 +1 ( = 2 or 3), lamellar perovskites, pyrochlores, spinels, and oxide solid solutions. Perovskite oxides are, by far, the most commonly used oxides. Therefore, this chapter will reflect this situation by putting more emphasis on this type of materials. Within this section the structure, preparation methods and general characteristics of the mixed oxides will be discussed. Note that R stands for rare-earth elements while A includes all types of elements. 

High pressure studies on magnetic transitions in rare earth metals, intra-rare earth alloys and compounds (the monochalcogenides, ferrites, spinels (RFe204) and garnets (R3Fe50i2 where R is a rare earth element)) have been numerous and all the work prior 1969 has been reviewed by Bloch and Pavlovic (1969). For the discussion on pressure studies of magnetic transition in this chapter, much material has been drawn from the above review. 

Nagasawa, H., H. D. Schreiber. and R. V. Morris, Experimental mineral/liquid partition coefficients of the rare earth elements (REE), Sc and Sr for perovskite, spinel and melilite. Earth Planet. Sci. Lett., 46, 431-437, 1980. 

Transparent, polycrystalline MgAL04 spinel (TPSp) can be used in various applications, like rare-earth and transition element ion host, windows transparent in the visible (VIS) or near-infrared (NIR) domains, etc. ... 

Coordination of the elements. In these compounds, the rare earths have then-usual coordination from 8 to 6. The magnesium is six coordinated (MnY2S4 and Ho4FeS7-types) or four-coordinated (spinel) as usual. In the solid solutions of the ThjP4-type Mg has an unusual 8-coordinated environment, which explains the small extent of the homogeneity range. 

The decomposition of the peroxide to hydroxide and oxygen is a key rate-limiting step in the reaction sequence. To accelerate the reduction of the peroxide species and the overall reaction rate, the air cathode is formulated using catalytic compounds which promote the reaction in step 2. These catalysts are typically metal compounds or complexes such as elemental silver, cobalt oxide, noble metals and their compounds, mixed metal compounds including rare earth metals, and transition metal macrocyclics, spinels, manganese tUoxide, phtalocyanines or perovskites." - ... 

With a relative abundance in the Earth s crust of 122 mg/kg, chromium is the 21st most abundant element and the 6th most abundant transition metal after iron, titanium, manganese, zirconium, and vanadium it is more abundant than nickel, zinc, and copper. Though native chromium is extremely rare (e.g, Udachnaya Mine in Russia), most common chromium-bearing minerals are the spinel-type mineral chromite [FeCr O, cubic] and, to a lesser... 

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