Partitioning olivine

Sometimes unravelling the separate effects of temperature and composition can be difficult, especially where the liquidus temperature of a melt is a function of composition. Such is the problem with Ni partitioning between olivine and a basaltic melt. Two experimental studies, published at the same time, seem to show conflicting results. Leeman and Lindstrom (1978) showed that the prime control on the olivine partition coefficient for Ni in a natural basaltic melt was temperature whilst Hart and Davis (1978) showed that there is clear inverse correlation between the melt composition and partition coefficient. To resolve the apparent conflict... 

Only McDade et al. (2003b) report experimental data on the partitioning of Nb and Ta between olivine and melt. At 1.5 GPa they find Dm = 1 x lO " and Dia = 6 x 10 ", which indicates that is smaller than rNb (0.660 A). This will serve to exclude Pa (rpa = 0.78 A) from the M-sites in much the same way as it is excluded from Ml in clinopyroxene. Furthermore D h and Dxa are themselves two orders of magnitude lower in olivine than coexisting clinopyroxene (McDade et al. 2003b). For these reasons we suggest that Pa is substantially more incompatible in olivine than clinopyroxene. 

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... 

Jones JH (1995) Experimental trace element partitioning. In Ahrens TJ (ed) Rock physics and phase relations A handbook of physical constants Am Geophys Union Reference Shelf 3 73-104 Kennedy AK, Lofgren GE, Wasserburg GJ (1993) An experimental study of trace element partitioning between olivine orthopyroxene and melt in chondrales equilibrium values and kinetic effects. Earth Planet Sci Lett 115 177-195... 

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. 

Arndt, N. T. (1977). Partitioning of nickel between olivine and ultrabasic and basic komatiitic liquids. Carnegie. Inst. Washington Year Book, 76, 553-57. 

Hart, S. R. Davis, K. E. (1978). Nickel partitioning between olivine and silicate melt. Earth Planet. Sci. Letters, 40, 203-19. 

Kinzler, R. J., Grove, T. L. Recca, S. I. (1990). An experimental study of the effect of temperature and melt composition on the partitioning of nickel between olivine and silicate melt. Geochim. Cosmochim. Acta, 54, 1255-65. 

Ulmer, P. (1989). The dependence of the Fe2+-Mg cation-partitioning between olivine and basaltic liquid on pressure, temperature and composition An experimental study to 30kbars. Contrib. Mineral. Petrol., 101, 261-73. 

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. 

Fuji T. (1977). Fe-Mg partitioning between olivine and spine Carnegie Inst. Wash. Yb.,... 

Grover J. E. and Orville T. M. (1969). The partitioning of cations between coexisting single and multisite phases with application to the assemblage Orthopyroxene-clinopyroxene and orthopyroxene-olivine. Geochim. Cosmochim. Acta, 33 205-226. 

Medaris L. G. (1969). Partitioning of Fe + and Mg between coexisting synthetic olivine and orthopyroxene. Amer. Jour. Set, 267 945-968. 

Nishizawa O. and Akimoto S. (1973). Partitioning of magnesium and iron between olivine and spinel, and between pyroxene and spinel. Contrib. Mineral Petrol, 41 217-240. 

O Neill H.St. C. and Wood B. J. (1979). An experimental study of Fe-Mg partitioning between garnet and olivine and its calibration as a geothermometer. Contrib. Mineral Petrol, 70 59-70. 

Righter, K., Campbell, A.J., Humayun, M., Hervig, R.L 2004. Partitioning of Ru, Rh, Pd, Re, Ir, and Au between Cr-bearing spinel, olivine, pyroxene and silicate melts. Geochimica et Cosmochimica Acta, 68, 867-880. 

Because Li isotopes may be used as a tracer to identify the existence of recycled material in the mantle, systematic studies of arc lavas have been undertaken (Morignti and Nakamura 1998 Tomascak et al. 2000 Leeman et al. 2004 and others). However, most arc lavas have 5 Li values that are indistinguishable from those of MORB. Thus Li seems to be decoupled from other fluid mobile elements, becanse Li can partition into Mg-silicates (pyroxene, olivine) in the mantle (Tomascak et al. 2002). 

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.

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