granodiorite

A Dictionary of Earth Sciences | 1999 | 615 words | Copyright

granodiorite A coarse-grained igneous rock consisting of essential quartz, plagioclase feldspar, alkali feldspar, biotite, and hornblende, with accessory sphene, apatite, and magnetite. Plagioclase is the dominant feldspar in the rock, equal to or greater than two-thirds of the total feldspar present. Where alkali feldspar is completely, or almost completely suppressed, the rock is known as a ‘trondhjemite’ or, more generally, ‘plagiogranite’. Granodiorites are commonly found as intrusions into the crust above subduction zones, and are the plutonic equivalent of extrusive dacites.

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AILSA ALLABY and MICHAEL ALLABY. "granodiorite." A Dictionary of Earth Sciences. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-granodiorite.html