Tonalite–trondhjemite–granodiorite

Tonalite–trondhjemite–granodiorite (TTG) rocks are intrusive rocks with typical granitic composition (quartz and feldspar) but containing only a small portion of potassium feldspar. Tonalite, trondhjemite, and granodiorite often occur together in geological records, indicating similar petrogenetic processes. Post Archean (after 2.5 Ga) TTG rocks are present in arc-related batholiths, as well as in ophiolites (although of a small proportion), while Archean TTG rocks are major components of Archean cratons.