Quartz diorite

Igneous, plutonic rock

Quartz diorite is an igneous, plutonic (intrusive) rock, of felsic composition, with phaneritic texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with 10% or less potassium feldspar. Quartz is present at between 5 and 20% of the rock. Biotite, amphiboles and pyroxenes are common dark accessory minerals.^[1]

Quartz diorite occurs in association with other granitic rock such as granodiorite, and with volcanic rock. In western North America a "quartz diorite line" occurs; west of this line, the dominant granitic rock is quartz diorite.^[2]

References

^ Williams, Howel; Turner, Francis J; Gilbert, Charles M (1954). Petrography; an introduction to the study of rocks in thin sections, by Howel Williams, Francis J. Turner, and Charles M. Gilbert. San Francisco: W.H. Freeman. OCLC 976619418.
^ https://www.jstor.org/stable/30063866?read-now=1&seq=2#page_scan_tab_contents James G. Moore (1959). The Quartz Diorite Boundary Line in the Western United States.The Journal of Geology, Vol. 67, No. 2 (Mar., 1959), pp. 198–210