Orthopyroxene trace elements

Diogenites as asteroidal cumulates insights from orthopyroxene trace element chemistry. Geochim. Cosmochim. Acta 59, 3071-3084. 

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... 

There are very few bulk analyses for coarsegrained olivine clasts from mesosiderites, and observed distinctions between them and pallasite olivines are mostly due to chromite and metal inclusions in the former (Mittlefehldt, 1980). Orthopyroxene clasts are generally similar to diogenites in major-, minor-, and trace-element composition (see Mittlefehldt et al., 1998). 

Kennedy A. K., Lofgren G. E., and Wasserburg G. J. (1993) An experimental study of trace element partitioning between olivine, orthopyroxene, and melt in chondrules. Earth Planet. Sci. Lett. 115, 177-195. 

Figure 21 Abundances of lithophile trace elements normalized to PM values in clinopyroxene, orthopyroxene, olivine, and spinel separated from a peridotite from the Ronda massif (Garrido et al., 2000). Normalizing values after...

The effects of post melt-depletion interaction with fluid or melt components in the lithospheric mantle has been extensively documented (e.g. Menzies Hawkesworth 1987, and references therein Harte et al. 1993 Pearson 1999 ) and it is widely accepted that these phenomena dominate the minor element geochemistry of cratonic peridotites. Extensive studies of the effect of metasomatism on the major element chemistry of lithospheric peridotites have also been made (Boyd Mertzman 1987 Keleman et al. 1992, 1998 Walter 1999). To date, most of the discussion has centred around the apparent excess of orthopyroxene, especially in Kaapvaal peridotites. However, major and trace element studies show that it is likely that the abundances of garnet and clinopyroxene are also grossly affected (Burgess Harte 1999 Shimizu 1999). 

In a rock containing SO % olivine, 30 % orthopyroxene and 20 % dinopyroxene, the bulk partition coeffident (D) for the trace element i would be... 

Colson er al. (1988) in a detailed study of trace element partitioning between olivine and silicic melt, and orthopyroxene and silicic melt, have shown that many partition coefficients are strongly dependent upon temperature and melt composition. They show that these partition coefficients vary according to ionic size and they have modelled temperature and composition dependence as a function of these variables. On the basis of their equations it is possible to predict partidon coefficients between olivine and melt, and orthopyroxene and melt, for a wide range of tri- arid di-valent cations under a7yiriety of magmatic conditions. 

Beattie, P., Trace element partitioning between silicate melts and olivines and orthopyroxenes, Geochim. Cosmochim. Acta, submitted, 1993fc. 

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