Trace element unmixing model compared to SMB samples. Tie lines relate the composition of liquid and solid in equilibrium with each other over a range of mass fraction crystallized MC. These compositions are calculated assuming fractional crystallization of a parental magma where no melt loss occurs. The assumed parental magma composition is listed in Table 2. The prior sections suggest that the transect samples analyzed are mixtures of two chemically distinct reservoirs along unmixing or tie lines and justifies this choice. The tie line in red associated with MC = 0.24 is the tie line that minimizes the least square error with respect to the analyzed samples in yellow.