Adakite

However, Defant and Drummond recognized that when young oceanic crust (less than 25 million years old) is subducted, adakites are typically produced in the arc.

[4] Drummond and Defant noted that Archean trondhjemites (which make up most of the ancient crust of continents) have similar geochemical characteristics to adakites.

The alternative interpretation is that the continental crust was derived from the partial melting of lower crustal basalts.

Garnet forms only under high pressures within the Earth and would not be stable in lower crust below some island arcs that erupt adakites.

[7] Adakites have also been reported from the continent-continent collision zone beneath Tibet and Lesser Caucasus.