Garnet partition coefficient

Dm (and Du) vary inversely with reciprocal temperature (Fig. 15). For mantle solidus garnets the correlation is reasonably good and can be used to make a first-order estimate of Dm- A more comprehensive model for Du and Dm, as a function of pressure, temperature and melt composition is provided by Salters et al. (2002). Their full expressions (for the molar partition coefficients, D ) are ... 

Figure 15. Variation in Dxh for garnet versns reciprocal temperature for experimental data sources listed in Table lb at a variety of pressures n = 33). A distinction is made between mantle solidus partition coefficients (Salters and Longhi 1999 Salters et al. 2002 McDade et al. 2003a,b) and the rest. Note the strong temperatnre dependence, which is qnalitatively similar to that incorporated in Equation (25b). The scatter is due to additional compositional controls.

Perhaps the biggest challenge in estimating U-series partition coefficients is the case of protactinium partitioning into garnet. The difficulty arises because the ionic radius of... 

Figure 16. Electrostatic model fitted to partition coefficients for cations entering the X-site in garnet, based on the experiments of Van Westrenen et al. (1999, 2000) and Klemme et al. (2002). The curves are fits to Equation (7) and can be used to estimate and f>o(x) > which f>pa(x) can be calculated via the lattice strain model. The fit parameters are given in Table 5.

Green TH, Blundy JD, Adam J, Yaxley GM (2000) SIMS determination of trace element partition coefficients between garnet clinopyroxene and hydrous basaltic liquids at 2-7.5 GPa and 1080-1200°C. Lithos 53 165-187... 

Table 2. Experimentally determined mineral/melt partition coefficients (x 10 ) for U, Th, and Ba in clinopyroxene and garnet and calculated bulk partition coefficients (xlO ) for a garnet peridotite source.

D s were calculated assuming 60% cpx, 40% garnet and no rutile using values from Keppler (1996) and gamet/melt cpx/melt partition coefficients to estimate gamet/fluid partitioning. ... 

Figure 4.11 Monte-Carlo simulation (100 trials) of error propagation for La/Yb fractionation in residual melts by clinopyroxene-garnet removal from a basaltic parent magma (see text for parameter description and distributions used). Top mineral-liquid partition coefficients for La and Yb. Bottom variations of the La/Yb ratio as a function of the fraction F of residual melt.

Harrison W. J. (1981). Partition coefficients for REE between garnets and liquids Implications of non-Henry s law behavior for models of basalt origin and evolution. Geochim. Cosmochim. Acta, 45 1529-1544. 

Oka Y. and Matsumoto T. (1974). Study on the compositional dependence of the apparent partitioning coefficient of iron and magnesium between coexisting garnet and clinopyro-xene solid solutions. Contrib. Mineral. Petrol, 48 115-121. 

Raheim A. and Green D. H. (1974). Experimental determination of the temperature and pressure dependence of the Ee-Mg partition coefficient for coexisting garnet and clinopyro-xene. Contrib. Mineral Petrol, 48 179-203. 

Figure 3-5 MnO partition between and diffusion in two minerals, olivine and garnet. Diffusional anisotropy of olivine is ignored. Initially, MnO in both phases were 0.2 wt%. As the two minerals come into contact, there will be diffusion to try to reach the equilibrium state. The partition coefficient (Mn)oiiv/(Mn)gt is assumed to be 0.59. The diffusivity in olivine is assumed to be 10 times that in garnet, resulting in a wider diffusion profile with a smaller slope in olivine.

Drake M. J. and McFarlane E. A. (1993) Mg-perovskite/siUcate melt and majorite garnet/silicate melt partition coefficients in the system CaO-MgO-Si02 at high temperatures and pressures. J. Geophys. Res. 98, 5427-5431. 

The Mg of orthopyroxene is similar or slightly greater than that of olivine, due to a relative Fe-Mg partition coefficient (Kd) of 1 that is independent of P and T (von Seckendorff and O Neill, 1993). The calcium content of orthopyroxene also varies depending on the temperature of equilibration of the sample and its bulk composition. In both the spinel- and garnet-facies, the CaO content increases with T and varies between 0.2 wt.% and 2.0 wt.%. Orthopyroxenes with very low CaO occur in harzburgites and/or in low-T samples in many kimberlite-borne xenolith suites. 

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