Partitioning Brice model

According to the Brice model, for an isovalent series of ions with charge n+ and radius n entering crystal lattice site M, the partition coefficient,, can be described in terms of three parameters (Fig. 3) , the radius of that site the elastic response... 

Figure 5 Brice model fits to the experimental data of Hauri et al. (1994) for clinopyroxene-melt partitioning. Note that the dependence of partitioning on charge corresponds to that found by Blundy and Wood (1994) (Figure 3). Deviation of Pb from the best-fit curve may be related to its electronic structure (see text).

Figure 4 Brice model fits to 1+, 2+, and 3+ cation partitioning between plagioclase (Ang9) and silicate melt in the system diopside-albite-anorthite (Blundy and Wood, 1994). Note that the best-fit curve becomes tighter as the charge on the cation increases from 1 + through 3+. This is due to increase in effective Young s modulus of the site with increasing charge (see text).

Figure 6 Brice model fits to garnet-melt partitioning of Van Westrenen et at. (2000b) for 2+ and 3+ ions.

In conclusion, we consider that E, D, and r can, for ions of constant charge partitioning into a given crystalline site, be parametrized using the Brice model. Our simulations and the preceding discussion serve to make us very cautious about trying to predict E and r values, however and we... 

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 ... 

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