Olivine fractionation

Table 1.2. Major-element data (%) for a Mauna Loa basalt and olivine phenocrysts. Composition of the residual liquids obtained after removal of olivine fractions f0(.

Table 1.11a. Major-element compositions (%) used for the example of olivine fractionation in the AFM diagram of Figure 1.10.

Equation (1.5.9) has been derived by Irvine (1977) and Pearce (1978) in the case of olivine fractionation from magmas and is also found in fluid-magma systems (Candela, 1986). 

Pearce, T. H. (1978). Olivine fractionation equations for basaltic and ultrabasic liquids. Nature, 276, 771-4. 

Several estimates for the olivine-H20 fractionation are shown these are emphasized by plotting them as short-dashed curves. One estimate ( a ) is taken from Rosenbaum et al. (1994) and is based on combination of theoretical fractionations a second (curve b ) combines measured C02-albite and albite-olivine fractionations (Chiba et al. 1989 Matthews et al. 1994) with the CO2-H2O fractionation calculated by (Richet et al. 1977) the third ( c ) combines the albite-water fractionation measured by Matsuhisa et al. (1979) with the albite-olivine fractionation from Chiba et al. (1989). All three of these approaches have their strengths and weaknesses I will consider the full range of values in the following discussion. 

Figure 3.22 Fields of partial melt and residue, calibrated in liquidus temperature and percentage meldng, for the pardat meldng of mande pyrolite plotted on a FeO-MgO diagram expressed in cadon mol Sb (calculated after the method of Hanson and Langmuir, 1978). The parent composition is where the two fields meet The curved lines with small tides show the trend of olivine fractional crystallization the ticks are at 5 % intervals (from Langmuir and Hanson, 1980).

Chondrite-normalized REE patterns calculated for olivine fractionation from a komadite melt komatiite-336) at 30%, 50%, 70% and 90% fracdonal crystalli2ation. The partition coefficients were taken from Table 4.1. The details of the calculations made for each of the ten REE shown using Eqn [4.18] are given in Table 4.15. 

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