How does palingenetic fusion occur in rock?
I have never seen the term "palingenetic fusion" anywhere in the geological literature, but seeing that it means:


  Palingenesis is a concept of rebirth or re-creation, used in various contexts in philosophy, theology, politics, and biology. Its meaning stems from Greek palin, meaning again, and genesis, meaning birth. 


And seeing that it is used to describe granitic charnockites, I think it is safe to say it is a very obscure term for anatexis, a common process of granite formation by partial melting of pre-existing rock. This is most commonly used in high grade metamorphic rocks, and in the context of formation of migmatites and leucogranites.