Olivine coefficients

Argon partition coefficients for olivine have recently been determined by Brooker et al. (1998). Their measured Z)at values are around 10 , which is higher than measured for clinopyroxene, but similar to the estimated values for orthopyroxene. We propose a value... 

Brooker RA, Wartho J-A, Carroll MR, Kelley SP, Draper DS (1998) Preliminary UVLAMP determinations of argon partition coefficients for olivine and clinopyroxene grown from silicate melts. Chem Geol 147 185-200... 

Michael PJ (1988) Partition coefficients for rare earth elements in mafic minerals of high silica rhyohtes the importance of accessory mineral inclusions. Geochim Cosmochim Acta 52 275-282 Mysen BO (1979) Nickel partitioning between olivine and silicate melt Henry s Law revisited. Am Mineral 64 1107-1114... 

Taura H, Yurimoto H, Kurita K, Sueno S (1998) Pressure dependence on partition coefficients for trace elements between olivine and the coexisting melts. Phys Chem Min 25 469-484 Taura H, Yurimoto H, Kato T, Sueno S (2001) Trace element partitioning between silicate perovskites and ultracalcic melt. Phys Planet Earth Int 124 25-32... 

This form of the partition coefficient, analogous to that used for Fe-Mg fractionation between olivine and melt (see Chapter 1), is necessary only for the rare cases where trace substitution affects Cj and Cp substantially. A number of reviews (O Nions and Powell, 1977 Michard, 1989) describe the various sorts of partition coefficients expressed either in mass-fractions, atom fractions, or normalized to a major element and their respective merits. If the discussion is restricted to a narrow range of chemical compositions (e.g., basaltic systems, Irving, 1978, Irving and Frey, 1984), enough experimental information exists on trace-element partitioning to resort to the wonderfully simple equation (9.1.1). 

From the concentration of each element in the liquid and in the source, we can retrieve the degree of melting and the residual mineralogy. We assume that the liquid contains 676 ppm Ni, 426 ppm Cr, 0.763 ppm Yb and 0.1 ppm Rb, whereas its source composition y vector is (2500, 1500, 0.2, 0.01) in ppm. We will test the assumption that the residuum is composed of olivine and clinopyroxene with the partition coefficients given above. Phase abundances Jt will be ordered as liquid, olivine and clinopyroxene. Let us compute, as an example, the element in the third row and second column of the matrix A... 

A basalt contains 150 ppm Ni, 100 ppm Sr, 3 ppm Yb, and 10 ppm Rb. Calculate the concentration of each element after removal of 20 percent of a cumulate containing 30 percent olivine, 20 percent clinopyroxene and 50 percent plagioclase in the residual liquid and in the average cumulate. Assume the partition coefficients given in Table 9.6. 

Mn Mgi )2Si04 olivine mixture obtained by Morioka (1981). The concentration profiles are symmetric, indicating that the diffusivities are independent of the concentration of the diffusing ion. On the contrary, possible asymmetry in the diffusion profiles indicate that concentration depends significantly on the diffusing cations. In this case, the interdiffusion coefficient can be obtained by the Boltzmann-Matano equation ... 

Table 5.7 Constants of equation relating coefficients to ionization potential and polarizability of cations in Ml and M2 sites in olivine. R is the correlation coefficient (from Della Giusta et al., 1990). ...

With increasing T and constant P, olivines expand their octahedral sites Ml and M2, whereas the tetrahedral group [8104] remains virtually unaffected. Table 5.9 lists linear thermal expansion coefficients for Ml-O and M2-0 polyhedra in some olivine compounds, according to Lager and Meagher (1978). These values are generally higher than those obtained by the method of Hazen and Prewitt (1977) (see eq. 1.93 and section 1.14.2). In particular, thermal expansion is anom-... 

Figure 10.13 Effect of oxygen fugacity on conventional partition coefficient of Cr. (A) Olivine/liquid partitioning experimental data of Bird (1971), Weill and McKay (1975), Huebner et al. (1976), Lindstrom (1976), and McKay and Weill (1976). (B) Subcalcic py-roxene/liquid partitioning experimental data of Schreiber (1976). Reprinted from A.J. Irving, Geochimica et Cosmochimica Acta, 42, 743-770, copyright 1978, with kind permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.

Davis L. L. and Smith D. (1993). Ni-rich olivine in minettes from Two Buttes, Colorado A connection between potassic melts from the mantle and low Ni partition coefficients. Geochim. Cosmochim. Acta, 57 123-129. 

When the concentration levels are higher, such as Ni diffusion between two olivine crystals with the same compositions except for Ni content (e.g., one contains 100 ppm and the other contains 2000 ppm), it may be referred to as either tracer diffusion or chemical diffusion. Tracer diffusivity is constant across the whole profile because the only variation along the profile is the concentration of a trace element that is not expected to affect the diffusion coefficient. 

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.

For inter diffusion between same-valence ions (ionic exchange) in an aqueous solution, or a melt, or a solid solution such as olivine (Fe +, Mg +)2Si04, an equation similar to Equation 3-135c has been derived from the Nemst-Planck equations first by Helfferich and Plesset (1958) and then with refinement by Barter et al. (1963) with the assumption that (i) the matrix (or solvent) concentration does not vary and (ii) cross-coefficient Lab (phenomenological coefficient in Equation 3-96a) is negligible, which is similar to the activity-based effective binary diffusion treatment. The equation takes the following form ... 

Consider He in a fluid inclusion in olivine in a basaltic melt. The radius of the inclusion is 50 fim. The olivine radius is 1 mm. The He partition coefficient between olivine and melt is estimated to be 0.0001. Assume that He diffusivity in olivine is 10 m /s. Find the reequilibration timescale. 

Petry C., Chakraborty S., and Palme H. (2004) Experimental detennination of Ni diffusion coefficients in olivine and their dependence on temperature, composition, oxygen fu-gacity, and crystallographic orientation. Geochim. Cosmochim. Acta 68, 4179-4188. 

We remember that minority point defect concentrations in compounds depend on the activity of their components. This may be illustrated by the solubility of hydrogen in olivine since it depends on the oxygen potential in a way explained by the association of the dissolved protons with O" and O- as minority defects [Q. Bai, D. L. Kohlstedt (1993)]. Similarly, tracer diffusion coefficients and mobilities of Si and O are expected to depend on the activity of Si02. The value (0 lnDf/0 In aSio2)> = Si and O, should give information on the disorder type as discussed in Section 2.3. 

Hiyagon and Ozima (1986) employed a laboratory approach of measuring crystal-melt partition coefficients. They measured noble gas concentration in olivine crystals and basalt melts, which were synthesized at 1370-1300°C under an atmospheric pressure, and also at 1360-1050°C under high pressure (0.2-1.5 GPa), of noble gas mixture. From these experimental results, they obtained ranges for noble gas partition coefficients XHe = 0.07, XNe = 0.006-0.08, KM = 0.05-0.15, KXe = 0.3. These partition coefficients are much larger than the values obtained by Marty and Lussiez (1993) and also these of common incompatible elements such as U (-0.002) or K (0.0002 - 0.008) between olivine and basalt melt (e.g. Henderson, 1982). 

The slopes of the linear correlation then gives activation energies E = 80 + 4 and 106 4kJ/mol for 4He and 20Ne, for the diffusion coefficient D = D0 exp(-E/RT). It is worth noting that the activation energies are much less than those estimated for olivine, a common rock-forming mineral (see Table 2.8). The time required for a gas... 

Hiyagon, H. (1994a) Constraints on rare gas partition coefficients from analysis of olivine-glass from a picritic mid-ocean ridge basalt - Comments. Chem. Geol., 112, 119-27. 

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