S.
No
Igneous Rock families
1
Defination:
2
Mineralogy
Granite – Rhyolite family
Granite
Rhyolite
Granodiorite
Plutonic , hypabyssal,
holocrystaliline, Phaneritic
Extrusive, hypabyssal,
holocrystalline to
hypocrystalline, aphanetic
Is intrusive,
Holocrystalline, phaneritic
Quartz
Potash feldspar
Sodic Plagioclase
1-Calc-alkali granite:
- Potash feldspar
(Perthitic orthoclase or
microcline.
- Biotite ± muscovite
(mafic min.).
- Oligoclase or rarely
andesine.
- H.B(green to brownish),
- Diopside or augite.
- Qtz is interstitial
2- Alkaligranite:
- Strongly Perthitic
(orth.,or micro.
- Allbite or Na oligocllase.
- Iron rich Biotite.
- Hastingsite,riebeckite.
- Aegirineaugite,aegirine.
- Quartz.
Accessory minerals
Granodiorite- Quartz Latite
- Magnetite,ilmenite,
hematite, pyrite, apatite,
monazite, zircon, allanite,
sphene, tourmaline,
fluorite, and garnet.
10-40%
30- 60%
35-10%
Potash Felds. 20 – 40 %
Sodic Plagio. 25 – 45 %
Quartz
10 - 35 %
Mafics (Bio, H.B) 10 – 30%
1- Potassic Rhyolite:
- Grano diorite Plagioclase
- Alkali feldspar
equal o exceed K'Sanidine untwined or
feldspar.
twinned Carlsbad
- But if k-feldspar is rare
twinning"
then the rock is called
- Plagioclase if present is
TONLITE
Oligoclase>
- Potash felds. Is
- Green biotite as
orthoclase & microcline,
phenocrysts andmatrix - Plagioclase is Oligoclase
flakes
or less andesine.
- Brown or green H.B.
- Browm biotite and green
2- Sodic Rhyolite:
HB.
- Same as above but,
- Pyroxene ( Diopside or
Amphibole minerals
augite)
are riebeckite,
- The
arfvdsedsonite,
orthoclase/plagiocalse
hastingsite.
ratio the rock will be
- Pyroxenes are not
named:
common in Rhyolite.
- 13¼ /66 tonalite
- 33 /66 Quartz mononite
- In Holocrystalline type:
Tridymite Qtz, Titanian,
magnetite, cordierite,
sphene, zircon, apatite,
garnet.
Apatite, magenetite,
ilmenite, sphene, and
garnet.
Quartz- Latite (Dellenite
and Rhyodacite)
Is extrusive, hypabyssal,
aphanitic matrix
holocrystalllline to
vitreous (porphyritic
Potash feldspar 20 – 30 %
Sodic Plagio. 30 – 50c%
Quartz
10 – 35 %
Mafics
10 – 20 %
Sanidine (is the usual kfelds.) appear as
phynocrysts.
Calcic andesine to
Oligoclase
Brown bio, & H.B as
phynpcrysts.
Sphene
Quartz (Tridymite)
Apatite, magenetite,
ilmenite, sphene, zircon,
3
Texture & microstructure
- Euhedral-granullar,fine
to coarse grained,
- Granophyritic rime,
plagioclase embayed with
orthoclase,
- Graphitic texture.
- Cataclastics
effect(undulatort qtz,
feldspar bent cleavageand
mica plate)
- Aplite texture: fine
grained , leucogranites
- Pegmatitic textur couse
grain dykes
- Rapakivi texture (large
oval shalle of orthoclase
surrounded by oligocllase
4
Occurrence
Granites occur in:
- Batholiths, stocks,
Hypabyssal bodies ( minor
intrusion sill & dikes)
- Porphyritic and great
- Equigranular, medium
- Porphyritic with
variety of matrix
grained
Holocrystalline,
textures are presented: - Subhedral to anhedral
cryptocrystalline,
1- Holocrystalline:
granular texture
vitreous
- Microgranular,
- Myrmekite texture
- Flow structures
- Trachytic
- Granophyric
- Spherulitic
- Cryptocrystalline
(devitrified.
2- Hypcrystalline:
- Hyalopilitic
(microcrystalline with
interstitial glass),
- Vitreous wt.
cryptocrystalline
patches.
- Vitreous wt. microlites.
- Vitreous wi.
Spherulites.
3- Rhyolite Vitrophyres
- Crystalites.
- Banded, streaked,
fluidal.
Rhyolite occurs as
Granodiorites occur in:
Rhyodacite occurs as
- Flow
Batholiths, stocks,
- Flow
- Volcanic type is
Hypabyssal bodies ( minor
- Volcanic rocks & also
hypabyssal intrusive
intrusion sill & dikes)
as dikes and sills.
dikes and sills.
Associted with Rhyolite
- Ass0cited with
dacite and trachyte and
andesite and basalt
basalt
S.
No
1
2
3
4
S.
No
1
2
3
4
Igneous Rock families
Syenite – Trachyte family
Syenite
Tonlite – Dacite family
Trachyte
Defination:
Mineralogy
Accessory minerals
Texture & microstructure
Occurrence
Igneous Rock families
Defination:
Mineralogy
Accessory minerals
Texture & microstructure
Occurrence
Syenite – Trachyte family
Syenite
Tonlite – Dacite family
Trachyte