GEOL 2312
IGNEOUS AND METAMORPHIC
PETROLOGY
Lecture 14
Origin of Granites
From H.H. Read (1955)
March 14, 2016
PARTIAL MELTING VS. FRACTIONAL CRYSTALLIZATION
THE SONJU LAKE – FINLAND GRANITE CONNECTION
Finland
Granite
The Problem: Even very efficient fractional
crystallization will create only ~5% felsic magma
PARTIAL MELTING VS. FRACTIONAL CRYSTALLIZATION
A few broad generalizations:
1) Most granitoids of significant volume occur in
areas where the continental crust has been
thickened by orogeny, either continental arc
subduction or collision of sialic masses. Many
granites, however, may post-date the
thickening event by tens of millions of years.
2) Because the crust is solid in its normal state,
some thermal disturbance is required to form
granitoids
3) Most workers are of the opinion that the
majority of granitoids are derived by crustal
anatexis, but that the mantle may also be
involved. The mantle contribution may range
from that of a source of heat for crustal
anatexis, or it may be the source of material
as well
Zoned zircon in a granite
with older inherited (restite)
core overgrown by new
material from the felsic
magma
ARC PLUTONIC
COMPLEXES“GRANITE”
BATHOLITHS
FEEDER
CHAMBERS TO
CONTINENTAL
ARC VOLCANICS
COMPOSITE
EMPLACEMENT OF
OF “GRANITOID”
BATHOLITHS
Granitoids – all intermediate to felsic
compositions plotting on a QAP(F) diagram
Tends toward more granitic compositions
over time
Epizonal batholiths form mostly by roof
collapse (stoping) or downdropping of the
chamber floor
GEOCHEMISTY OF ARC PLUTONIC COMPLEXES
MIMICS VOLCANIC COMPOSITIONS
Peruvian Coastal
Batholith
NON-GENETIC CLASSIFICATIONS
OF GRANITOID ROCKS
Chemistry-based
Mineralogy-based
ESSENTIAL MINERALOGY OF GRANITIC ROCKS
LINKED TO THE QAP TERNARY EUTECTIC/MINIMUM
Felsic Magma
Generated from
Mafic Magmas
Felsic Magma
Generated from
melting Crust
GENETIC CLASSIFICATION OF GRANITIC ROCKS
BASED ON SOURCE ROCK/MODE OF ORIGIN
Table 18-3. The S-I-A-M Classification of Granitoids
SiO2
K2O/Na2O
Type
M
46-70%
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
low
< 9‰
low
high
> 9‰
var
low
var
Ca, Sr
high
A/(C+N+K)*
low
low: metal- moderate
uminous to
peraluminous
I
53-76%
low
high in
mafic
rocks
S
65-74%
high
low
high
low
metaluminous
A
high
 77%
Na2O
high
* molar Al2O3/(CaO+Na2O+K2O)
low
var
peralkaline
87
Sr/86Sr
Misc
Petrogenesis
< 0.705
Low Rb, Th, U
Subduction zone
Low LIL and HFS or ocean-intraplate
Mantle-derived
< 0.705
high LIL/HFS
Subduction zone
med. Rb, Th, U
Infracrustal
hornblende
Mafic to intermed.
magnetite
igneous source
> 0.707 variable LIL/HFS Subduction zone
high Rb, Th, U
biotite, cordierite
Supracrustal
Als, Grt, Ilmenite sedimentary source
var
low LIL/HFS
Anorogenic
high Fe/Mg
Stable craton
high Ga/Al
Rift zone
High REE, Zr
High F, Cl
Data from White and Chappell (1983), Clarke (1992), Whalen (1985)
M-TYPE GRANITOIDS
Table 18-3. The S-I-A-M
Classification
of Granitoids
DIFFERENTIATES
OF
MAFIC
MAGMAS
SiO2
K2O/Na2O
Type
M
46-70%
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
low
< 9‰
low
high
> 9‰
var
low
var
Ca, Sr
high
A/(C+N+K)*
low
low: metal- moderate
uminous to
peraluminous
I
53-76%
low
high in
mafic
rocks
S
65-74%
high
low
high
low
metaluminous
A
high
 77%
Na2O
high
* molar Al2O3/(CaO+Na2O+K2O)
low
var
peralkaline
87
Sr/86Sr
Misc
Petrogenesis
< 0.705
Low Rb, Th, U
Subduction zone
Low LIL and HFS or ocean-intraplate
Mantle-derived
< 0.705
high LIL/HFS
Subduction zone
med. Rb, Th, U
Infracrustal
hornblende
Mafic to intermed.
magnetite
igneous source
> 0.707 variable LIL/HFS Subduction zone
high Rb, Th, U
biotite, cordierite
Supracrustal
Als, Grt, Ilmenite sedimentary source
var
low LIL/HFS
Anorogenic
high Fe/Mg
Stable craton
high Ga/Al
Rift zone
High REE, Zr
High F, Cl
Data from White and Chappell (1983), Clarke (1992), Whalen (1985)
Type
M
Table 18-3. The S-I-A-M Classification of Granitoids
I-T
YPE GRANITOIDS
Sr/ Sr
SiO
K O/Na O Ca, Sr A/(C+N+K)* Fe /Fe
Cr, Ni  O
Misc
Petrogenesis
Table 18-3.
The S-I-A-MU
Classification
of Granitoids
R
EMELTING
OF
M
AFIC
NDERPLATED
C
RUST
46-70%
low
high
low
low
low
< 9‰ < 0.705
Low Rb, Th, U
Subduction zone
3+
2
2
2+
18
87
86
2
SiO2
K2O/Na2O
Type
M
46-70%
low
I
53-76%
low
Ca, Sr
high
high in
mafic
rocks
high in
mafic
low
rocks
3+
2+
A/(C+N+K)* Fe /Fe
low
low
low: metal- moderate
uminous to
peraluminous
low: metal- moderate
uminous
high to
low
peraluminous
I
53-76%
low
S
65-74%
high
S
65-74%
high
low
A
high
 77%
Na2O
high
low
var
metaluminous
peralkaline
var
A
high
 77%
Na2O
high
low
var
peralkaline
var
* molar Al2O3/(CaO+Na2O+K2O)
* molar Al2O3/(CaO+Na2O+K2O)
metaluminous
high
low
Low LIL and HFS or ocean-intraplate
Misc
Petrogenesis
Mantle-derived
< 0.705
Low Rb, Th, U
Subduction zone
< 0.705
high LIL/HFS
Subduction zone
Low LIL and HFS or ocean-intraplate
med. Rb, Th, U
Infracrustal
Mantle-derived
hornblende
Mafic to intermed.
low
< 9‰ < 0.705
high
LIL/HFS
Subduction
zone
magnetite
igneous source
Rb,LIL/HFS
Th, U
Infracrustal
high
> 9‰ > 0.707 med.
variable
Subduction
zone
hornblende
Mafic
to intermed.
high Rb, Th, U
magnetite
igneous
source
biotite,
cordierite
Supracrustal
high
> 9‰ > 0.707 variable
Subduction source
zone
Als, Grt, LIL/HFS
Ilmenite sedimentary
high
Th, U
low
var
var
low Rb,
LIL/HFS
Anorogenic
biotite, cordierite
Supracrustal
high Fe/Mg
Stable craton
Als, Grt, Ilmenite sedimentary source
high Ga/Al
Rift zone
low
var
var
low
LIL/HFS
Anorogenic
High REE, Zr
high
Stable craton
HighFe/Mg
F, Cl
high
Ga/Al
Rift(1985)
zone
Data from White and Chappell (1983),
Clarke
(1992), Whalen
High REE, Zr
High F, Cl
Cr, Ni
low
low
18O
< 9‰
< 9‰
87
Sr/86Sr
Data from White and Chappell (1983), Clarke (1992), Whalen (1985)
Mantle-derived
I
53-76%
low
high in
low: metal- moderate
low
< 9‰ < 0.705
high LIL/HFS
Subduction zone
mafic
uminous to
med. Rb, Th, U
Infracrustal
rocks peraluminous
hornblende
Mafic to intermed.
magnetite
igneous source
S
65-74%
high
low
high
low
high
> 9‰ > 0.707 variable LIL/HFS Subduction zone
Table 18-3. The S-I-A-M Classification of Granitoids
high Rb, Th, U
metaluminous
biotite, cordierite
Supracrustal
3+
2+
87
18
Sr/86Sr Als, Grt,
SiO2
K2O/Na2O Ca, Sr A/(C+N+K)* Fe /Fe
Type
Cr, Ni  O
Misc
Petrogenesis
Ilmenite sedimentary source
M
46-70%
low
high
low
low
low
<
9‰
<
0.705
Low
Rb,
Th, U
Subduction
zone
Na2O
A
high
low
var
var
low
var
var
low LIL/HFS
Anorogenic
Lowhigh
LILFe/Mg
and HFS or Stable
ocean-intraplate
 77%
high
peralkaline
craton
Mantle-derived
high Ga/Al
Rift zone
I
53-76%
low
high in
low: metal- moderate
low
< 9‰ < 0.705
high LIL/HFS
Subduction zone
High
REE, Zr
mafic
uminous to
med.High
Rb,F,
Th,
Infracrustal
ClU
rocks
peraluminous
hornblende
Mafic
to(1985)
intermed.
* molar Al2O3/(CaO+Na2O+K2O)
Data from White and Chappell (1983), Clarke (1992), Whalen
magnetite
igneous source
S
65-74%
high
low
high
low
high
> 9‰ > 0.707 variable LIL/HFS Subduction zone
high Rb, Th, U
metaluminous
biotite, cordierite
Supracrustal
Als, Grt, Ilmenite sedimentary source
Na2O
A
high
low
var
var
low
var
var
low LIL/HFS
Anorogenic
 77%
high
peralkaline
high Fe/Mg
Stable craton
high Ga/Al
Rift zone
High REE, Zr
High F, Cl
A-TYPE GRANITOIDS
ANOROGENIC MELTING OF CONTINENTAL INTERIORS
* molar Al2O3/(CaO+Na2O+K2O)
Data from White and Chappell (1983), Clarke (1992), Whalen (1985)
M-Type
M
46-70%
low
high
low
low
low
< 9‰
< 0.705
Low Rb, Th, U
Subduction zone
Low LIL and HFS or ocean-intraplate
Mantle-derived
I
53-76%
low
high in
low: metal- moderate
low
< 9‰ < 0.705
high LIL/HFS
Subduction zone
Table
18-3.
The
S-I-A-M
Classification
of
Granitoids
mafic
uminous to
med. Rb, Th, U
Infracrustal
rocks peraluminous
hornblende
Mafic
to intermed.
3+
2+
87
86
18
Fe
/Fe
Sr/
Sr

O
SiO
K
O/Na
O
Type
Ca, Sr A/(C+N+K)*
Cr, Ni
Misc
Petrogenesis
2
2
2
magnetite
igneous
source
M
46-70%
low
high
low
low
< 9‰ >
< 0.707
0.705 variable
Low Rb,LIL/HFS
Th, U
S
65-74%
high
low
high
low
high
>
Subduction zone
Low
and
highLIL
Rb,
Th,HFS
U or ocean-intraplate
metaluminous
biotite, cordierite
Supracrustal
Mantle-derived
Grt,
Ilmenite sedimentary
I
53-76%
low
high in
low: metal- moderate
low
< 9‰ < 0.705 Als,
high
LIL/HFS
Subduction source
zone
Na2O
mafic
uminous
med.
Rb,
Th, U of Hydrous
Infracrustal
A
high
low
var to
var
low
varDehydration
var
lowMelting
LIL/HFS
Anorogenic
rocks
peraluminous
hornblende
Mafic
to intermed.
 77%
high
peralkaline
high Fe/Mg
Stable
craton
Mineral-bearing
Metasedimentary
magnetite
igneous
source
high Ga/Al
Rift zone
Rocks
S
65-74%
high
low
high
low
high
> 9‰ > 0.707 variable
LIL/HFS
Subduction zone
High
REE,
Zr
high
Rb,F,Th,
High
Cl U
metaluminous
biotite,Clarke
cordierite
Supracrustal
* molar Al2O3/(CaO+Na2O+K2O)
Data from White and Chappell (1983),
(1992), Whalen
(1985)
Als, Grt, Ilmenite sedimentary source
Na2O
A
high
low
var
var
low
var
var
low LIL/HFS
Anorogenic
 77%
high
peralkaline
high Fe/Mg
Stable craton
high Ga/Al
Rift zone
High REE, Zr
High F, Cl
S-TYPE GRANITOIDS
PARTIAL MELTING OF SEDIMENTARY ROCKS
* molar Al2O3/(CaO+Na2O+K2O)
Data from White and Chappell (1983), Clarke (1992), Whalen (1985)
High-grade metasedimentary rocks have little-no free
water, so water-saturated melting curve (a-b-c) not as
important as hydrous mineral melting curves
Melt generation along the 40°C/km geotherm
TRACE
ELEMENT
GEOCHEMISTRY
OF SIAM
GRANITOIDS
Strongly enriched in
incompatible trace elements,
especially LILE and LREE, U
and Th.
Negative anomalies in Sr
and Ba (follows Ca) and TiNb-Ta (except intraplate
granitoids)
TRACE ELEMENT TECTONIC DISCRIMINATION
DIAGRAMS FOR GRANITOIDS
GRANITES CREATED DURING CONTINENT-CONTINENT
COLLISION (OROGENESIS)
POST-
OROGENIC
GRANTOIDS
EXTENSIONAL
COLLAPSE
PostPenokean
granites