Petrology Flashcards by Elena Guillen

coarse, igneous
>90% plag
<10% olivine and pyx
what is the rock name?

Anorthosite

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silica unsaturated plutonic rocks is called

Nepheline syenite

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coarse, igneous
equal k-felds and plag

Monzonite

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coarse, cryptocrystalline rock
<90% mafics
>60% felsics being foids

Foidolite

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Monzogranite is often called

Adamellite

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rare, coarse, crystalline, igneous
>90% quartz composed of felsic
<90% mafic minerals
hydrothermally altered (greisen)

Quartzolite

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light colored granitoid
plag is <10% of total felds

Alkali-feldspar granite

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K-felds/Total felds ratio is 0.35-0.90
20-60% quartz
coarse, holocrystalline, felsic, acidic, plutonic

Granite

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granitoid
k-felds/total felds ratio 0.65-0.90
20-60% quartz

Syenogranite

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k-felds/total felds is 0.35-0.65
often called adamellite

Monzogranite

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20-60% quartz
plag is 65-90% total felds
intermediate bet. tonalite & granite containing quartz

Granodiorite

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~ extrusive equivalent of granodiorite

rhyodacite

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granitoid, plag >90% of total felds

Tonalite

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syenitic-rock
no quartz
10% foids

Foid-bearing K-felds syenite

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K-felds/Plag ratio 65-90%
5% quartz
intrusive equivalent of trachyte

Syenite

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syenite
no quartz, <10% foids

Foid-bearning syenite

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equal k-felds and plag
intermediate bet. syenite and diorite
quartz is minor or absent
intrusive equivalent of latite

Monzonite

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dioritic
<5% quartz
10-35% K-felds

Monzodiorite

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syenitoid
5-20% quartz
subequal k-felds and plag (35-65% of felds being plag)
no foids
coarse-grained equivalent of quartz-latite

Quartz-monzonite

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gabbroid
felsic minerals less than 5% quartz or no foids
10-35% K-felds
optional term for a variety of granite having roughly equal amounts of k-felds and plag

Monzogabbro

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dioritic
5-20% quartz
10-35% k-felds

Quartz monzodiorite

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gabbro
felsic minerals compromising more than 5% quartz
10-35% k-felds

Quartz monzogabbro

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gabbroid
10-90% Ca-dominant plag
>5% clinopyroxene
intrusive/coarse-grained equivalent of Basalt

Gabbro

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mostly of calcic plag (>90% usually labradorite)
<10% mafics
lunar highlands are composed predominantly of this

Anorthosite

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dioritic 0-10% quartz 10-35% k-felds

Quartz Diorite

gabbro more than 5% quartz

Quartz gabbro

diorite <10% foids <10% k-felds

Foid-bearing diorite

gabbro up to 10% foid minerals

Foid-bearing gabbro

foid-syenitic-rock k-felds is >90%

Foid syenite

foid-syenitoid k-felds is >50-90%

Foid monzonite

foid-dioritoid k-felds is >50-10%

Foid monzodiorite

foid-rich rock >60% of light coloured minerals are foids coarse, crystalline <90% mafics >60% felsics being foids

Foidolite

family of rock-forming minerals too little silica to form feldspar not a true group

Foids (Feldspathoids)

Fine-grained equivalent of syenite

Trachyte

Fine-grained felsic igneous rocks lacking quartz, with felsics comprimosing 10-60% foids and k-felds/total felds >0.9

Phonolite

Fine-grained equivalent of diorite

Andesite

fine-grained, igneous felsics >20% quartz <0.5 k-felds/plag

Dacite

fine-grained, igneous felsics 10-60% foids k-felds/total felds <0.1 <10% olivine

Tephrite

>20% quartz 40-90% k-felds/plag extrusive

Rhyolite

>20% quartz <0.5 k-felds/plag extrusive of granodiorite

Dacite

0-5% quartz 0.65-0.90 k-felds/total felds extrusive of syenite

Trachyte

0-5% quartz 0.35-0.65 k-felds/total felds extrusive of monzonite

Latite

fine-grained equivalent of diorite 0-20% quartz >65% felds being plag

Andesite

general for fine-grained, mafic, igneous rocks common - extrusive (volcanic) locally intrusive (e.g. as dikes or pipe) fine-grained equivalent of gabbro

Basalt

10-60% foids >0.9 k-felds/total felds fine-grained equivalent of nepheline syenite

Phonolite

10-60% foids <0.1 k-felds/total felds <10% olivine extrusive equivalent of theralite

Tephrite

tephritic rock 10-60% foids <0.1 k-felds/total felds >10% olivine similar to tephrite but with little to no olivine similar to basalt but little to no foids

Basanite

<90% mafics >90% foids of felsics

Foidite

TAS stands for

Total Alkali versus Silica

Classification scheme for volcanic rocks based on their bulk chemical composition

TAS diagram

How are volcanic rocks classified

classified by their chemistry

Why can't volcanic rocks be classified by their mineralogy?

because the rocks is finely crystallized or even made of volcanic glass

crystals so small they cannot be seen with the naked eye

Aphanitic

phenocrysts contain numerous inclusions of another mineral that they enveloped with growth

Poikilitic

plagioclase overgrowths on orthoclase (k-felds)

Rapakivi

texture of andesite is commonly

Porphyritic

common texture of komatite

Spinifex

description of the degree of crystallinity, grain size and shape, and arrangement of minerals

Texture

crystals visible to the naked eye

phaneritic

coarse grained

3cm to 5mm

medium grained

1-5 mm

fine grained

< 1mm

crystals so small they cannot be seen

Aphanitic

composed entirely of crystals

Holocrystalline

composed entirely of glass

Holohyaline

composed of crystals and glass

Hypocrystalline

phenocrysts set in a glassy groundmass

Vitrophyric

phenocrysts contain numerous inclusions of another mineral that they enveloped with growth host crystal is call an Oikocryst

Poikilitic

holes in rock formed by escaping gases during solidification

Vesicles

Rock that is Felsic and Phaneritic

Granite

Intermediate, Phaneritic

Diorite

Mafic, Phaneritic

Gabbro

Felsic, Aphanitic

Rhyolite

Aphanitic, Intermediate

Andesite

Mafic, Aphanitic

Basalt

Porphyritic, Felsic

Granite Porphyry

Intermediate, Porphyritic

Andesite porphyry

Mafic, porphyritic

Basalt porhyry

ultramafic lava, such as precambrian komatiites, develop elongated olivine crystals result of rapid growth of olivine in low viscosity magma, not by slow cooling

Spinifex

preferred nucleation of one mineral on a preexisitng mineral ex. growth of sillimanite on biotite or muscovite

Epitaxis

plag overgrowths on orthoclase occurs on some granites

Rapakivi

in silicic volcanic rocks in w/c needles of quartz and k-felds grow rapidly from a common center

Spherulitic

radiating plag lath in some basalts probably the result of nucleation of later crystals on the first nuclei to form during devitrification of glass

Variolitic

envelopment of plag lath by larger cpx and commonly interpreted to indicate that cpx formed late

Ophitic

simultaneous crystallization of feldspar and quartz intergrowth forms epitaxially on preexisting phenocrysts or dikelet walls

granophyre

coarser version of granophyre

graphic

evidence for advanced resorption, or rapid growth enveloping melt due to undercooling

sieve texture

microphenocrysts of plag are aligned due to flow

Trachytic

microphenocrysts are randomly oriented

Felty or pilotaxitic

Petrology Flashcards

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