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The quartz percentage among felsic minerals in TTG rocks is usually larger than 20% but less than 60%. [1] In tonalite and trondhjemite, more than 90% of the feldspars are plagioclase, while in granodiorite, this number is between 65% and 90%. [1] Trondhjemite is a special kind of tonalite, with most of the plagioclase in the rock being ...
Trondhjemite is a leucocratic (light-colored) intrusive igneous rock. It is a variety of tonalite in which the plagioclase is mostly in the form of oligoclase . [ 1 ] Trondhjemites that occur in the oceanic crust or in ophiolites are usually called plagiogranites .
Trondhjemite is an orthoclase-deficient variety of sodium-rich tonalite with minor biotite as the only mafic mineral, named after Norway's third largest city, Trondheim. [6] Tonalites, together with granodiorites, are characteristic of calc-alkaline batholiths formed above subduction zones. [7]
Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene.The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite.
Felsite covered with dendritic pyrolusite Dike of felsite on Islay in Scotland. Felsite is a very fine-grained volcanic rock that may or may not contain larger crystals.Felsite is a field term for a light-colored rock that typically requires petrographic examination or chemical analysis for more precise definition.
Monzonite is found in association with gabbro and granodiorite in the Khankandi pluton in the Alborz Mountains of Iran. The monzonite likely formed during the collision that closed the Tethys Ocean, from partial melting of upper mantle that had previously been altered by fluids released from a subducting ocean crust slab.
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A sample of rhyodacite from Slovakia. Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite.It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite.