Fig. 1 and fig. 2 given below represent schematic phase relations in two binary systems at identical and constant pressure. a and b have eutectic relationship w

Fig. 1 and Fig. 2 given below represent schematic phase relations in two binary systems at identical and constant pressure. A and B have eutectic relationship while C and D form a solid solution. The temperature scale (Y-axis) is same in both figures. R1, R2, R3 and R4 represent four rock compositions in these two systems. Write the sequence in which melts will start forming in these rocks (RI, R2, R3 and R4) with increasing temperature (without changing pressure). Explain with justification, the order in which the solid component will completely melt (under equilibrium condition) in R1, R2, R3 and R4 as heating proceeds. Liquid Liquid A R1 R2 B C R3 R4 D Fig. Fig. 2