Xenoliths and inclusions within a plutonic or volcanic rock provide evidence for the assimilation process. Heat of melting is the heat capacity of of the solid phases plus the heat of crystallization of the minerals involved.
Heat of mixing is the heat required to mix the phases.
Q, F and B will be melted, the heat for melting comes from the heat generated by the crystallization of olivine and pyroxene from the liquid, not from the temperature of the basaltic liquid. The end result is a basaltic andesite with inclusions of chewed up, partially digested granitic material. The heats of crystallization of quartz, feldspar and biotite from a granitic liquid are not large enough to melt the basalt inclusions, resulting in very minor changes in the original liquid composition. The result is a granite with amphibolite inclusions. Any changes caused by assimilation and hybridization are dependant on the nature of the inclusions and the nature of the magmatic liquid into which the inclusions are emplaced.