IUGS Classification Coarse Grain/ Texture Flashcards
Quartz compromise more than 90% of the felsic minerals, and has <90% mafic minerals. It may be hydrothermally altered granitoids (e.g. greisen)
Quartzolite
A light colored mineral where plagioclase is less than 10% of the total feldspar.
Alkali-feldspar granite
An alkali-feldspar/ total feldspar ratio from 0.35-0.90 on the QAFP diagram and 20 - 60% quartz
Granite
An alkali-feldspar/ total feldspar ratio from 0.65 - 0.90 and 20 - 60 quartz
Syenogranite
An alkali-feldspar/ total feldspar ratio from 0.35-0.65 on the QAFP diagram. Often called adamellite.
Monzogranite
It has 20-60% quartz and a plagioclase of 65-90% of the total feldspar.
Grandiorite
A granitoid, where plagioclase is >90%
Tomalite
Plagioclase is less than 10% of the total feldspar
Alkali-feldspar syenite
No quartz and containing up to 10% foids
Foid-bearing alkali feldspar syenite
Alkali-feldspar/ plagioclase ratio from 65-90% and <5% quartz. Intrusive equivalent of ‘trachyte’
Syenite
No quartz and <10% foids
Foid-bearing syenite
Equal amounts of alkali feldspar and plagioclase, and thus intermediate between diorite and syenite. Intrusive equivalent og latite.
Monzonite
Dioritic rock with <5% quartz and 10-35% alkali feldspar on the QAFP diagram.
Monzodiorite
A syenitoid with 5-20% quartz and subequal K-feldspar and plagioclase (35-65% of the feldspar being plagioclase). Coarse-grained equivalent of quartz-latite.
Quartz-monzonite
Less than 5% quartz or no foids, and no 10-35% K-feldspar.
Monzogabbro
Dioritic rock with 5-20% quartz and 10-35% alkali feldspar.
Quartz monzodiorite
More than 5% quartz and 10-35% K-Feldspar
Quartz monzogabbro
Foid-dioritoid where K-feldspar is >50-10% of feldspar
Foid monzodiorite
Foid gabbroic rock where plagioclase is 50-90% of feldspar
Foid monzogabbro
<5% quartz and <10% alkali feldspar on the QAFP diagram
Diorite
Composed of 10-90% Ca-dominant plagioclase and >5% clinopyroxene
Gabbro
Mostly of calcic plagioclase (>90% usually labradiorite) with <10% mafics
Anorthosite
Dioritic rock with 0-10% quartz and 10-35% alkali feldspar.
Quartz Diorite
Gabbro with felsic minerals comprising more than 5% quartz
Quartz Gabbro
Diorite with <10% foids and <10% alkali feldspar
Foid-bearing diorite
Gabbro containing up to 10% foid minerals
Foid-bearing gabbro
Rock where K-feldspar is >90%
Foid syenite
Foid-syenitoid where K-feldspar is >50-90% of feldspar
Foid monzosyenite
Foid-dioritoid where k-feldspar is 50-90%
Foid monzodiorite
Plagioclase is >90% of feldspar
Foid diorite
Rock with <90% mafics, >60% of felsic being foids
Foidolite
Minerals consisting of aluminosilicates of sodium, potassium, or calcium and having too little silica to form feldspar.
Foids (feldspathoids)
and Enumerate the common foid mineralss
Analcime
Leucite
Nepheline
Sodalite
Crystals visible to the naked eye.
Phaneritic
Crystals so small that they cannot be seen with the naked eye
Aphanitic
Composed entirely of crystals
Holocrystalline
Composed entirely of glass
Holohyaline
Composed of crystal and glass
Hypocrytalline
Phenocrysts set in a glassy groundmass
Vitrophyric
Phenocrysts containing numerous inclusion of another mineral that they enveloped with growth.
Poikilitic
Host crystal of poikilitc is termed as _________.
Poikilitc
Holes in the rock formed by escaping gases during solidification
Vesicle
Result of rapid growth of olivine and develop elongated olivine crystals
Spinifex texture
Nucleation of one mineral on a preexisting mineral e.g. growth of sillimanite on biotite or muscovite
Epitaxis texture
Plagioclase overgrowths on orthoclase (K-feldspar)
Rapakivi texture
In silicic volcanic rocks in which needles of quartz and alkali feldspar growth radially from a common center
Spherulitic texture
Refers to the envelopment of plagioclase laths by larger larger clinopyroxene and is commonly interpreted to indicate that clinopyroxene formed later.
Ophitic texture
Radiating plagioclase laths in some basalts are probably the result of nucleation of later crystals on the first nuclei to form during devitrification of glass
Variolitic texture
Evidence for advanced resorption, or rapid growth enveloping melt due to undercooling
Sieve texture
Result from simultaneous crystallization of feldspar and quartz, the intergrowth forms epitaxially preexisitng phenocrysts or dikelet walls
Granophyre and Graphic Texture
