Quartz monzonite

{{Short description|Type of igneous rock}}{{Infobox rock

|name=Quartz monzonite

|type=Igneous

|image=Quartz monzonite 36mw1037.jpg

|caption=Quartz monzonite bedrock from a USGS drill core at western Cape Cod, Massachusetts

}}

File:granite for temple.jpg

Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagioclase is typically intermediate to sodic in composition, andesine to oligoclase. Quartz is present in significant amounts. Biotite and/or hornblende constitute the dark minerals. Because of its coloring, it is often confused with granite, but whereas granite contains more than 20% quartz, quartz monzonite is only 5–20% quartz. Rock with less than five percent quartz is classified as monzonite. A rock with more alkali feldspar is a syenite whereas one with more plagioclase is a quartz diorite.[http://geology.csupomona.edu/alert/igneous/igclass.htm Classification of Igneous Rocks] {{webarchive |url=https://web.archive.org/web/20110930102012/http://geology.csupomona.edu/alert/igneous/igclass.htm |date=September 30, 2011 }} The fine grained volcanic rock equivalent of quartz monzonite is quartz latite.

The term adamellite was originally applied by A. Cathrein in 1890 to orthoclase-bearing tonalite (likely a granodiorite) at Monte Adamello, Italy, in 1890, but later came to refer to quartz monzonite. The term is now deprecated.{{cite journal |last1=Streckeisen |first1=A. |title=To each plutonic rock its proper name |journal=Earth-Science Reviews |date=1 March 1976 |volume=12 |issue=1 |pages=1–33 |doi=10.1016/0012-8252(76)90052-0}}

Quartz monzonite porphyry is often associated with copper mineralization in the porphyry copper ore deposits.Titley, Spencer R. and Carol L. Hicks, Geology of the Porphyry Copper Deposits, University of Arizona Press, 1966, p. 35