If the granite contains two feldspars (alkali feldspars and plagioclase) could be considered subsolvus, which as your mentioned case.. The second type peralkaline granite the mesoperthite is formed via metamsomatic processes it is not of magmatic origin . In this case belong to the group of two feldspars.

This is two feldspar granite. Mostly the occurrence of K concentration in granite due to alteration as well as chemical weathering. The Na and Ca concentration in granite is due to chemical fractionation. These features mostly you can found in mineralised zone.

Alkali feldspars usually exhibit in optical and sub optical inter growth of albite and k-feldspar (as perthite). If dry rocks with alkali feldspar or ternary feldspar are cooled slowly, the feldspar undergo extensive exsolution and coarsening so that the exsolved phases become visible under optical microscope forming mesoperthite, even though the individual crystal may retain their original form and bulk composition. Presence of coarsely exsolved mesoperthite recommended to assign the phase equally between A and P as amount of alkali feldspar and plagioclase (usually oligoclase or andesine) components are roughly the same.