1.The diagram above is a 3 component compositional phase diagram, with 3 components (X,Y,Z) and four phases (A,B,C,D) plus liquid. Line P-Q-R is a peritectic/reaction curve, while lines R-S and S-T are cotectics. Arrowheads point in the direction of decreasing temperature. Phase D melts incongruently. a) Express the compositions of phases A, B, C and D in percentages of the components X, Y and Z. (2 marks) A = X___ Y___ Z___ B = X___ Y___ Z___ C = X___ Y___ Z___ D = X___ Y___ Z___ b) On the diagram above, mark the compositional path of the magma as it crystallizes in equilibrium with the solid species, starting at bulk composition G. (2 marks)

c) Starting at point G, at point Q, how much liquid is left (as a percentage of the initial amount), and how much of minerals A and D have crystallized (again, as a percentage of the initial amount) if all mineral phases remain in constant equilibrium with the liquid. (1 mark) Liquid _____ % A ______ % D ______ % d) Once all the liquid has crystallized, what is the percentage of each of the minerals present, given the original bulk composition G, H and J if all mineral phases remain in constant equilibrium with the liquid? (2 marks) G: A ______% B _______ % C ______ % D _______ % H: A ______% B _______ % C ______ % D _______ % J: A ______% B _______ % C ______ % D _______ % e) Beginning with a rock of bulk composition H, assuming FRACTIONAL MELTING, how many distinct melts are produced, and what are their compositions? (1 mark) Draw the compositional path of the SOLID on the above diagram (1 marks) How many distinct melts ______ Composition of Melts: Melt No. 1: X______% Y _______ % Z ______ % (Or Letter ________) Melt No. 2: X ______% Y _______ % Z ______ % (Or Letter ________) Melt No. 3: X ______% Y _______ % Z ______ % (Or Letter ________) Melt No. 4: X ______% Y _______ % Z ______ % (Or Letter ________)

Z Go D 10 R O S B Y