Figure 9. Modeling of rare-earth element (REE) variation for combined assimilation and fractional crystallization (AFC). The partitioning coefficients are from Martin (1987). Fractionation assumes 70% plagioclase and 30% augite. REE normalization values are from Sun and McDonough (1989). A. The samples used in the modeling: the andesitic to dacitic flows from the Middle Series (Fitton et al., 1998b) (Units 47 and 55), granophyre CL87-52E from Blichert-Toft et al. (1992, table 2), and Archean felsic gneiss 324721 from Blichert-Toft et al. (1995, table 2). The composition of Unit 89 is from Fitton et al. (1998b). B. AFC modeling using the granophyre as contaminant and Unit 89 as the differentiating magma. The model results are shown for 50% crystallization and constant assimilation/fractionation ratios (R = 0 to 0.5 in step of 0.1). C. The same modeling as in (B) shown for constant R = 0.5 and variable liquid remaining (F = 1.0 to 0.5 in increments of 0.1). D. AFC modeling using the gneiss as contaminant. The modeling variables are as for (B).