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.[1] Tonalite, trondhjemite, and granodiorite often occur together in geological records, indicating similar petrogenetic processes.[1] 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.[1]

Archean TTG rock outcrop in Kongling Complex, South China Craton. The white TTG rock body is intruded by dark mafic dikes, as well as light color felsic dikes. The mafic minerals in the TTG rock body, possibly biotite, were weathered, which introduced a brownish coating on the TTG rock surface.

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