Fig. 46

C1 chondrite-normalized REE plots for crystallization models (Taylor 1985). FLR equals the fraction of liquid remaining, and the black lines describe the degree of fractionation. The gray field outlines the theoretical melt compositions based on the gabbro augite compositions. a In situ fractionation model, where only 30% of the interstitial melt is returned from the mush-zone to the central magma. b Assimilation-fractionation model, where crystallization of the DMM-derived melt takes place during bulk assimilation of the average olivine gabbro from Hole 735B (Natland and Dick 2001). The diagram demonstrates that even if the melt assimilated pre-existing olivine gabbro, the gabbros represent melts that first fractionated 50% elsewhere, but then crystallized to near completion