Partitioning of elements

Ayers JC, Dittmer SK, Layne GD (1997) Partitioning of elements between peridotite and H2O at 2.0-3.0 GPa and 900-1000°C, and application to models of subduction zone processes. Earth Planet Sci Lett 150 381-398... 

There are empirical relationships which relate alloy content to T, but these are not usually applicable to all types of Ti alloy and can suffer from a lack of accuracy. Significantly, there are no such relationships which can be generally used for predicting the amount of a and 13 in commercial alloys as a function of temperature and composition and little work has been undertaken to quantitatively understand the partitioning of elements between the a and 0 phases. 

These examples involve partitioning of elements as liquids cooled and crystallized. Partial melting of a solid rock also results in partitioning of incompatible elements into the liquid phase, which contains no rigid crystalline sites. Separation of the melt then fractionates incompatible elements from the compatible elements left behind in the solid residue. 

Anhydrous planetesimals, and especially the meteorites derived from them, provide crucial cosmochemical data. Spectroscopic studies of asteroids do not provide chemical analyses, but the spectral similarities of several asteroid classes to known meteorite types provide indirect evidence of their compositions. The few chemical analyses of asteroids by spacecraft are consistent with ordinary chondrite or primitive achondrite compositions. Laboratory analyses of anhydrous meteorites - chondrites, achondrites, irons, and stony irons - allow us to study important chemical fractionations in early solar system bodies. Fractionations among chondrites occur mostly in elements with higher volatility, reflecting the accretion of various components whose compositions were determined by high- and low-temperature processes such as condensation and evaporation. Fractionations among achondrites and irons are more complex and involve partitioning of elements between melts and crystals during differentiation. 

Nevertheless, we can make some general statements about the geochemistry of differentiated planets. The planetesimals from which they accreted had compositions determined largely by element volatility. Once assembled into a planet and heated, the partitioning of elements into cores and mantles was governed by their siderophile or lithophile affinities. Further differentiation of mantles to form crusts was controlled by the compatible or incompatible behavior of elements. 

Sequential extraction experiments have been shown to provide a convenient means to determine the metals associated with the principal accumulative phases in sedimentary deposits, to elucidate the mechanisms of their diagenetic transformation, and to elucidate release processes upon changing environmental conditions (Kersten and Forstner, 1989). A general goal of all studies involving selective chemical extraction is the accurate determination of partitioning of elements of environmental concern among different discrete phases of a sample. 

The partitioning of elements between aqueous solution and crystals and between silicate melts and crystalline solids in the light of thermodynamic theory was excellently reviewed by McIntyre (1963). 

Jasmund, K., Seek, H. A. Partition of Elements in Coexisting Feldspars as Determined by Experiment and in Trachytic Rocks. 24th Intern. Geol. Congr., Montreal, Sect. 10, Geochemistry, pp. 78-84 (1972). 

A fuller knowledge of the structure and bonding in silicate melts should enable detailed description and prediction of the chemical processes involved in magmatic crystallization and of the partitioning of elements between melt and crystals. A large body of experimental data is, in fact, available on this subject, but the only significant contributions so far made by application of bonding theories center on the simple ionic models... 

Ohtani E., Kawabe I., Moriyama J., and Nagata Y. (1989) Partitioning of elements between majorite garnet and melt... 

In thermodynamically based models, it is critical to account for the P- and T-dependence of the partitioning of elements among minerals, as well as the mass balance of reactions among minerals. A set of equations corresponds to each of these requirements. The principles have been detailed elsewhere (Spear, 1993), and so the equations are simply presented here. 

Concerning cation coordination in silicate melts, most work in the past has concentrated on partitioning of elements between the melt and various numbers of silicates in equilibrium with it. Bums has analyzed these phenomena in detail in terms of crystal field stabilization energies pertaining to the solid phases. However, only a few studies on coordination sites in the melt have been reported and much of our knowledge of these systems is based on theoretical consideration of potential geometries developed in random rigid-sphere assemblies. 

Information content is a fundamental measure derived from the partitioning of elements into equivalence classes several - molecular descriptors are derived as -t information indices. 

Gasparik T. and Drake M. J. (1995) Partitioning of elements among two silicate perovskites, superphase B, and volatile-bearing melt at 23 GPa and 1,500-1,600 °C. Earth Planet Sci. Lett 134, 307-318. 

The study of partitioning of elements between and among metamorphic phases has two useful objectives. First, it ascertains whether the compositions are consistent with the phases having achieved chemical equilibrium. Second, the partitioning may be sensitive to temperature and/or pressure, and thus be useful for thermobarometry. 

Partitioning of Elements Between Aqueous Solution and Crystal... 

Partitioning of Element Between Aqueous Solution and Solid Solution Mineral... 

Partitioning of Elements Between Aqueous Solution and Crystal Distribution coefficient (Kd) is given by... 

Chapter 1 provides an extensive discussion of chemical equilibria as they pertain to minerals. This covers in detail chemical equilibria of solids and aqueous solutions, the solubility of various types of minerals, the weathering of silicate and aluminosilicate minerals, the composition of geothermal and groimd water, hydro-thermal alteration, oxidation and reduction reactions, and the partitioning of elements between aqueous solutions and crystals. 

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