Skip to content

Geology is the Way


Granodiorite is a type of plutonic igneous rock with felsic to intermediate composition, representing – together with tonalite – the plutonic counterpart of dacite. Its name comes from the union of the words ‘granite‘ (granum = grain) and ‘diorite’, since its composition is halfway between these rock types. Granodiorites contain quartz, plagioclase, alkali feldspars, and femic minerals (most commonly biotite and/or hornblende). In the QAPF diagram, a rock can be classified as a granodiorite if quartz represents 20 to 60% of the felsic minerals and plagioclase is 65 to 90% of all feldspars. Plagioclase in granodiorites normally shows sodium-rich compositions (oligoclase to andesine). If the plagioclase composition is richer in calcium (above An50) the rock can be classified as a granogabbro, a very rare igneous rock.

Biotite-bearing granodiorite outcropping at Graniteville, Vermont (USA). Barre Pluton, New Hampshire Plutonic Series (Devonian). Photo © James St. John.
Granodiorite with well-visible prismatic crystals of black amphibole. Tobacco Root Batholith (Late Cretaceous), Madison County, Montana, USA. Photo © James St. John.

Plutonic igneous rock
Felsic minerals:
• sodic plagioclase
alkali feldspar
Mafic minerals:

QAPF classification:
Q = 20 – 60%
Plagioclase/feldspars = 65 – 90%
Colored varieties:
• leucogranodiorite (M < 5%)
• melagranodiorite (M > 25%)
Other varieties:
Extrusive equivalent: dacite

Granodiorite with quartz, plagioclase, alkali feldspar, and hornblende amphibole. Giant Forest Granodiorite (middle Cretaceous). Moro Rock, Sequoia National Park, California, USA. Photo © James St. John.
Neves granodiorite
Biotite granodiorite from Neves, Sud Tirol, Italy.

Frost, T. P., & Mahood, G. A. (1987). Field, chemical, and physical constraints on mafic-felsic magma interaction in the Lamarck Granodiorite, Sierra Nevada, California. Geological Society of America Bulletin99(2), 272-291.
Glazner, A. F., Coleman, D. S., & Bartley, J. M. (2008). The tenuous connection between high-silica rhyolites and granodiorite plutons. Geology36(2), 183-186.
Martin, H., Smithies, R. H., Rapp, R., Moyen, J. F., & Champion, D. (2005). An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos79(1-2), 1-24.
Streckeisen, A. (1976). To each plutonic rock its proper name. Earth-science reviews12(1), 1-33.


Igneous Minerals
Igneous Textures
Plutonic Rocks
Igneous Bodies


Do you like this page?

italian flag

Traduzione in corso!

Le pagine in Italiano dovrebbero essere disponibili nuovamente nel giro di qualche mese.