Granitization - the conversion of country rock to granite. Upward migration From subducting slabs. By buoyancy and pushing aside the country rock. Similar to the emplacement of salt domes. Spreading center volcanism.
Plates pull apart and basaltic magma moves up to fill the voids.
Short path to the surface. Produces mid-oceanic ridges. Water-rich plates descend into the hot mantle and melting occurs. Long path to the surface. Dominant magma is andesitic - much assimilation.