Apatite partition coefficient

This argument was explored by Reynard et al. (1999), using values of E and Vg obtained from the experimental partitioning data of Fujimaki (1986). Reynard et al. (1999) used Equation (1) to predict equilibrium REE-apatite partition coefficients at surface temperature and pressure, assuming that the crystal chemistry of bone apatite is broadly similar to that of HAP, and that crystal-melt partition coefficients can be used to estimate crystal-water partitioning. Reynard et al. (1999) then compared the predicted partition coefficients with measured adsorption coefficients for the REE between seawater and HAP derived by Koeppenkastrop and DeCarlo (1992), and concluded that incorporation of REE into bone via a substitution mechanism produces bell shaped REE patterns with relatively little fractionation between La and Lu. Incorporation of REE into bone via an adsorption mechanism, on the other hand, produces significant fractionation between La and Lu (La/Lu = 5). Based on REE patterns found in fossil fish teeth, they concluded that REE uptake in fossil bone was dominated by adsorption mechanisms, but that subsequent recrystallization may superimpose a degree of substitution-related fractionation over the initial, adsorption related REE pattern. It is important to note, however, that these predictions are based on crystal chemistry of hydroxyapatite and fluorapatite, and not dahllite and francolite. Variations in E and Vo will affect relative adsorption and/or partition coefficients, and may alter the predicted partition coefficient ratios (e.g., La/Lu and La/Sm). 

Chazot G., Menzies M. A., and Harte B. (1996) Determination of partition coefficients between apatite, clinopyroxene, amphibole and melt in natural spinel Uierzolites from Yemen implications for wet melting of the lithospheric mantle. Geochim. Cosmochim. Acta 60, 423-437. 

Watson EB, Green TH (1981) Apatite/hquid partition coefficients for the rare earth elements and strontium. Earth Planet Sci Lett 56 405-421... 

An appreciation of the mechanisms of trace element-bone interaction can be gained by comparing uptake of REE in bone with experimental and analytical studies of high temperature apatite-melt REE partitioning behavior. Apatite-melt partition coefficients derived from experimental studies, when plotted against ion radius, show parabolic traces with maxima around Nd-Sm (Fig. 3). These REE ions have radii closest to Ca, and indicate that REE are held in Ca sites in the lattice. Blundy and Wood (1994) developed a predictive model for calculation of equilibrium partition coefficients of trace elements between crystals and melt in igneous systems. In this model, the partitioning behavior of isovalent cations between a mineral and liquid at a particular pressure, temperature, and composition of interest can be explained by a version of the Brice (1975) equation, in which the size and elasticity of the crystal lattice sites play a critical role ... 

Figure 3. Apatite-melt partition coefficients derived from high temperature experimental and natural systems (A-C) and estimates of partitioning between ichthyoliths and bottom water (D), together with the best fit of Equation (1) (Blundy and Wood 1994) to this data. Values taken from ...

Fowler SW, Buat-Menard P, Yokoyama Y, Ballestra S, Holm E, Van Nguyen H (1987) Rapid removal of Chernobyl fallout from Mediterranean sttrface waters by biological activity. Nature 335 622-625 Fujimaki H (1986) Partition coefficients of Hf, Zr, and REE between zircon, apatite, and liquid. Contrib Mineral Petrol 94 42-45... 

Fujimaki H., 1986, Partition coefficients of Hf, Zr and REE between zircon, apatite and liquid. Contrib. Mineral. Petrol., 94, 42-45. 

Watson et al. [143] also give rqiproximate apatite/liquid partition coefficients for Pb of 0.1-0.4. However, again, oxygen fugacity was not controlled. 

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