Granodiorite
Chemical Process (Liquid-phase Growth) - Closed system under ground (Melt precipitation)
Synonym
Quartz diorite
Definition
Igneous rocks with equigranular texture having mineral compositions as follows: Quartz in felsic minerals = 10-60 vol%, Plagioclase in feldspar = 65-90 vol%. Other characters summarized below are those of general granodiorites, and the rock type may be inferred but cannot be determined by mafic mineral assemblages.
Mineral composition
Mafic minerals < 30 vol% (Felsic), Quartz in felsic minerals = 10-60 vol%, Plagioclase in feldspar = 65-90 vol%.
Chemical composition
SiO2 > 66 wt% (Acidic).
Texture
Equigranular texture composed of grains more than a few mm.
Required Geological Setting
Occurrence
Rock forming minerals in granodiorite, felsic (acidic) plutonic rock formed from magma under ground. Granodiorite distributes in continents and island arcs associated with Granite batholiths and stocks.
Distribution of granodiorites described in this site. Red is ilmenite-series granites corresponding to S-type granites, and blue is magnetite-series granites corresponding to I-type granites.
Mineral Assemblages
Quartz, K-feldspar, Plagioclase (Oligoclase), Biotite, hornblende, (Pyroxene)
Localities
- Mount Ogi (Cummingtonite)