Download ppt

GEOL 5310
ADVANCED IGNEOUS AND
METAMORPHIC PETROLOGY
Subduction-related Igneous Activity
and the Origin of Granite
November 16, 2009
PRESENT-DAY SUBDUCTION ZONES
Winter (2001) Figure 16-1. Principal subduction zones associated with
orogenic volcanism and plutonism. Triangles are on the overriding plate.
After Wilson (1989) Igneous Petrogenesis, Allen Unwin/Kluwer.
CHANGING MODELS OF ARC MAGMATISM
1960-70’s Arc magmas
largely derived from
subducted oceanic crust
and sediment
1980-90’s Arc magmas
largely derived from
mantle wedge
1990’s- 2000’s both
contribute, but wedge is
dominant source
STRUCTURE OF AN ISLAND ARC
Winter (2001) Figure 16-2. Schematic cross section through a typical island arc after Gill (1981), Orogenic Andesites and Plate
Tectonics. Springer-Verlag. HFU= heat flow unit (4.2 x 10-6 joules/cm2/sec)
VOLCANIC ROCKS OF ISLAND ARCS



Complex tectonic situation and broad spectrum of volcanic products
High proportion of basaltic andesite and andesite
Basalts common and an important part of the story
Table 16-1. Relative Proportions of Analyzed
Island Arc Volcanic Rock Types
Locality
B
B-A
A
D
R
2
Mt. Misery, Antilles (lavas)
17
22
49
12
0
2
Ave. Antilles
17
( 42 )
39
2
1
Lesser Antilles
71
22
5
( 3 )
1
Nicaragua/NW Costa Rica
64
33
3
1
0
1
W Panama/SE Costa Rica
34
49
16
0
0
1
Aleutians E of Adak
55
36
9
0
0
1
Aleutians, Adak & W
18
27
41
14
0
2
Little Sitkin Island, Aleutians
0
78
4
18
0
2
Ave. Japan (lava, ash falls)
14
( 85 )
2
0
1
Isu-Bonin/Mariana
47
36
15
1
<1
1
Kuriles
34
38
25
3
<1
2
Talasea, Papua
9
23
55
9
4
1
Scotia
65
33
3
0
0
1
from Kelemen (2003a and personal comunication).
2
after Gill (1981, Table 4.4)
A = andesite,
D = dacite,
B = basalt B-A = basaltic andesite
R = rhyolite
MAJOR ELEMENTS AND MAGMA SERIES
Characteristic
Plate Margin
Series
Convergent Divergent
Alkaline
yes
Tholeiitic
yes
yes
Calc-alkaline
yes
Figure 16-3. Data compiled by Terry
Plank (Plank and Langmuir, 1988)
Earth Planet. Sci. Lett., 90, 349-370.
Within Plate
Oceanic Continental
yes
yes
yes
yes
THOLEIITIC VS. CALC-ALKALINE MAGMA SERIES
Fractional Melting
of Hydrous Mantle
Figure 16.6. c. FeO*/MgO vs. SiO2 diagram distinguishing tholeiitic
and calc-alkaline series. The gray arrow near the bottom is the
progressive fractional melting trend under hydrous conditions of
Grove et al. (2003).
Winter (2010) Figure 16.6. b. AFM diagram distinguishing tholeiitic and calc-alkaline
series. Arrows represent differentiation trends within a series.
K MAGMA SERIES
IN ISLAND ARC BASALT - ANDESITE
Figure 16.5. Combined K2O - FeO*/MgO
diagram in which the Low-K to High-K series
are combined with the tholeiitic vs. calc-alkaline
types, resulting in six andesite series, after Gill
(1981) Orogenic Andesites and Plate Tectonics.
Springer-Verlag. The points represent the
analyses in the appendix of Gill (1981).
Figure 16.6. a. K2O-SiO2 diagram distinguishing high-K, medium-K and low-K series. Large
squares = high-K, stars = med.-K, diamonds = low-K series from Table 16-2. Smaller
symbols are identified in the caption. Differentiation within a series (presumably dominated
by fractional crystallization) is indicated by the arrow. Different primary magmas (to the left)
are distinguished by vertical variations in K2O at low SiO2. After Gill, 1981, Orogenic
Andesites and Plate Tectonics. Springer-Verlag.
DIFFERENTIATION TRENDS FOR IAV
Early Fe-Ti Ox
FX in Calc-Alk
CaPl  NaPl
Pl+Cpx FX
Figure 16-6. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
TRACE ELEMENT CHARACTERISTICS
Depleted Mantle
Undepleted Mantle or Low % PM of DM?
GARNET in
source?
Low % PM of Undepleted mantle?
Winter (2010) Figure 16-10.
TRACE ELEMENT CHARACTERISTICS
HYDROUS MORB SOURCE, SELECTIVELY ENRICHED MORB SOURCE,
OR OIB SOURCE W/ HFS-COMPATIBLE RESIDUAL MINERAL?
Hydrophilic
LIL Elements
Nb(Ta)
HFS Elements
Anomalies
Figure 16-11a. MORB-normalized spider diagrams for selected island arc basalts. Using the normalization and ordering scheme of Pearce (1983) with
LIL on the left and HFS on the right and compatibility increasing outward from Ba-Th. Data from BVTP. Composite OIB from Fig 14-3 in yellow.
PETROGENESIS OF ISLAND ARC MAGMAS
THERMAL MODEL FOR SUBDUCTION
Variables affecting isotherms
in subduction zones:
• Rate of subduction
• Age of the subduction
zone
• Age of the subducting
slab
• Flow in the mantle wedge
• Frictional/shear heating
along the Wadati-Benioff
zone
Other factors:
 dip of the slab
 endothermic
metamorphic reactions
 metamorphic fluid flow
Isotherms will be higher when:
• convergence is slower
• slab is younger (nearer to ridge)
• arc is younger
Winter (2010) Figure 16-15. Cross section of a subduction zone showing isotherms (red-after
Furukawa, 1993, J. Geophys. Res., 98, 8309-8319) and mantle flow lines (yellow- after Tatsumi and
Eggins, 1995, Subduction Zone Magmatism. Blackwell. Oxford).
POTENTIAL SOURCES OF ARC MAGMAS
Only Viable Sources
1. Crustal portion of the
subducted slab
Altered
oceanic crust
(hydrated by circulating
seawater, and metamorphosed
in large part to greenschist
facies)
Subducted
oceanic and
forearc sediments
Seawater
trapped in pore
spaces
2. Mantle wedge between slab
and arc crust
3. Arc crust
4.Lithospheric mantle of
subducting plate
5. Asthenosphere beneath slab
Winter (2010) Figure 16-15. Cross section of a subduction zone showing isotherms (red-after
Furukawa, 1993, J. Geophys. Res., 98, 8309-8319) and mantle flow lines (yellow- after Tatsumi and
Eggins, 1995, Subduction Zone Magmatism. Blackwell. Oxford).
P-T-t PATHS FOR SUBDUCTED CRUST
Subduction rate of 3 cm/yr
(length of each curve = ~15 Ma)
Subducted Crust
Yellow paths =
various arc ages
Red paths =
different ages of
subducted slab
Figure 16-16. Subducted crust pressuretemperature-time (P-T-t) paths for
various situations of arc age (yellow
curves) and age of subducted lithosphere
(red curves, for a mature ca. 50 Ma old
arc) assuming a subduction rate of 3
cm/yr (Peacock, 1991, Phil. Trans. Roy.
Soc. London, 335, 341-353).
MELTING OF SUBDUCTED CRUST
ONLY FOR YOUNG CRUST AND ARCS
D- Dehydration Zone - no
melting; LIL-enriched
fluids move into mantle
wedge.
M – Partial melting of
basaltic slab  Mg
andesite
Winter (2010) Figure 16-16. Subducted
crust pressure-temperature-time (P-T-t)
paths for various situations of arc age
(yellow curves) and age of subducted
lithosphere (red curves, for a mature ca. 50
Ma old arc) assuming a subduction rate of
3 cm/yr (Peacock, 1991). Included are
some pertinent reaction curves, including
the wet and dry basalt solidi (Figure 7-20),
the dehydration of hornblende (Lambert
and Wyllie, 1968, 1970, 1972), chlorite +
quartz (Delaney and Helgeson, 1978).
Winter (2001). An Introduction to Igneous
and Metamorphic Petrology. Prentice Hall.
VISCOSITY AT SLAB-MANTLE INTERFACE
ENHANCING MANTLE FLOW AND T
7 Km into
Slab
Winter (2001) Figure 16.17. P-T-t paths at a depth
of 7 km into the slab (subscript = 1) and at the
slab/mantle-wedge interface (subscript = 2)
predicted by several published dynamic models of
fairly rapid subduction (9-10 cm/yr). ME= Molnar
and England’s (1992) analytical solution with no
wedge convection. PW = Peacock and Wang
(1999) isoviscous numeric model. vK = van Keken
et al. (2002a) isoviscous remodel of PW with
improved resolution. vKT = van Keken et al.
(2002a) model with non-Newtonian temperatureand stress-dependent wedge viscosity. After van
Keken et al. (2002a) © AGU with permission.
Slab Surface
No Mantle Flow
MELTING OF HYDRATED MANTLE WEDGE
MAIN SOURCE OF ARC MAGMAS
Figure 16-11b. A proposed model
for subduction zone magmatism
with particular reference to island
arcs. Dehydration of slab crust
causes hydration of the mantle
(violet), which undergoes partial
melting as amphibole (A) and
phlogopite (B) dehydrate. From
Tatsumi (1989), J. Geophys. Res.,
94, 4697-4707 and Tatsumi and
Eggins (1995). Subduction Zone
Magmatism. Blackwell. Oxford.
MELTING OF MANTLE WEDGE
MAIN SOURCE OF ARC MAGMAS
B
T
A
Melting at 3 main locations
T - Mantle Tip
A - Pargasite-out depth
(~110km)
B - Phlogopite-out depth
(~200 km)
T
Winter (2010) Figure 16.19
MELTING OF HYDRATED MANTLE WEDGE
MAIN SOURCE OF ARC MAGMAS
Primary Magma=
High-Mg (>8wt%)
High-Al tholeiite
from Garnet
Lherzolite Source
From which more
evolved tholeiitic
and calc-alkaline
magmas are
formed by
fractional
crystallization?
Figure 16-11b. A proposed model
for subduction zone magmatism
with particular reference to island
arcs. Dehydration of slab crust
causes hydration of the mantle
(violet), which undergoes partial
melting as amphibole (A) and
phlogopite (B) dehydrate. From
Tatsumi (1989), J. Geophys. Res.,
94, 4697-4707 and Tatsumi and
Eggins (1995). Subduction Zone
Magmatism. Blackwell. Oxford.
Sp
Gt
CONTINENTAL ARCS VS ISLAND ARCS
AFFECTS OF THICK DIFFERENTIATED
CONTINENTAL CRUST




Thick sialic crust contrasts
greatly with mantle-derived
partial melts may produce more
pronounced effects of
contamination
Low density of crust may retard
ascent causing stagnation of
magmas and more potential for
differentiation
Low melting point of crust allows
for partial melting and crustallyderived melts
Subcontinental lithosphere may
be more compositionally diverse
that suboceanic lithosphere,
especially if crust is old
TYPES OF CONTINENTAL ARCS
Destructive
more common where
Continental crust is older
e.g. Andean Margin
Constructive
more common where
Continental crust is younger
e.g. Pacific NW
ANDEAN
CONTINENTAL ARC
Gaps in volcanic activity
• shallow subduction
• overthickened slab
ANDEAN VOLCANIC COMPOSITIONS
DISTRIBUTION OF ROCK TYPES
Melting of Lower
Crust generates
Felsic Magmas
Lower Crust traps
Mafic Magmas
ANDEAN VOLCANIC COMPOSITIONS
MAJOR ELEMENTS
Northern Volcanic Zone
• more andesitic to felsic
• K-rich comps to east
Alkaline Rocks
Central Volcanic Zone
• more andesitic to felsic
• basalts rare
• more staging beneath
Precambrian crust
Southern Volcanic Zone
• broad range of comps
• K-rich comps to east
• shallower subduction
angle
• Young continental
crust especially
to south
Island Arcs
ANDEAN VOLCANIC COMPOSITIONS
TRACE ELEMENTS
CVZ – Assimilation of
Precambrian crust
and SCLM
SVZ - Shallower
subduction angle 
melting of Gt-free
mantle
Winter (2010) Figure 17.4. Chondrite-normalized REE diagram for selected Andean volcanics. NVZ (6 samples, average SiO2 = 60.7, K2O = 0.66, data from
Thorpe et al. 1984; Geist, pers. comm.). CVZ (10 samples, ave. SiO2 = 54.8, K2O = 2.77, data from Deruelle, 1982; Davidson, pers. comm.; Thorpe et al.,
1984). SVZ (49 samples, average SiO2 = 52.1, K2O = 1.07, data from Hickey et al. 1986; Deruelle, 1982; López-Escobar et al. 1981).
ANDEAN VOLCANIC COMPOSITIONS
TRACE ELEMENTS
CVZ – Assimilation of
Precambrian crust
and/or SCLM
Enriched LIL and mobile
HFS dehydration of
subducted slab and
enrichment of mantle wedge
Negative Nb-Ta anomaly similar to island arc pattern
Winter (2010) Figure 17.5. MORB-normalized spider diagram (Pearce, 1983) for selected Andean volcanics. NVZ (6 samples, average SiO 2 = 60.7, K2O =
0.66, data from Thorpe et al. 1984; Geist, pers. comm.). CVZ (10 samples, ave. SiO2 = 54.8, K2O = 2.77, data from Deruelle, 1982; Davidson, pers. comm.;
Thorpe et al., 1984). SVZ (49 samples, average SiO2 = 52.1, K2O = 1.07, data from Hickey et al. 1986; Deruelle, 1982; López-Escobar et al. 1981).
ANDEAN VOLCANIC COMPOSITIONS
ISOTOPIC COMPOSITIONS
Winter (2010) Figure 17.6. Sr vs. Nd isotopic ratios for the three zones of the Andes. Data from James et al. (1976), Hawkesworth et al. (1979), James (1982),
Harmon et al. (1984), Frey et al. (1984), Thorpe et al. (1984), Hickey et al. (1986), Hildreth and Moorbath (1988), Geist (pers. comm), Davidson (pers.
comm.), Wörner et al. (1988), Walker et al. (1991), deSilva (1991), Kay et al. (1991), Davidson and deSilva (1992).
CONSTRUCTIVE
CONTINENTAL
ARC
PACIFIC NW
Juan de Fuca Plate –
Young, hot, bouyant;
dehydrates quickly upon
subduction
Columbia Embayment area of young crust
and arc construction by
rollback or trench
jumping
CASCADE MAGMA TYPES OVER TIME
Greater proportion of
mafic compositions &
bimodal volcanism
More akin to
Continental Flood
Basalt provinces
Interpreted to indicate
mafic underplating
leading to lower crustal
melting in an
extensional
environment
Bimodal Volcanism
CASCADES TRACE ELEMENT GEOCHEMISTRY
Deplete (MORB) and
Enriched (OIB) Signatures
= Heterogeneous Mantle
Wedge?
Nb-Ta anomaly
not common
= Early shallow
dehydration of
hot slab?
CASCADES ISOTOPE GEOCHEMISTRY
Precambrian
Crustal Signature
87/86Srº
> 0.706
206/204Pbº
> 18.9
GENERAL MODEL FOR
CONTINENTAL ARC MAGMATISM
M-crustal Melting
A- Assimilation
S- Storage
H-Homogenization
ORIGIN OF GRANITES
Frontpiece from H.H. Read (1958) The Granite Controversy
PARTIAL MELTING VS. FRACTIONAL CRYSTALLIZATION
THE SONJU LAKE – FINLAND GRANITE CONNECTION
Finland
Granite
The Problem: Even very efficient fractional
crystallization will create only 5-10% felsic magma
A FEW BROAD GENERALIZATIONS ABOUT GRANITES
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
GEOCHEMISTY OF ARC PLUTONIC COMPLEXES
MIMICS VOLCANIC COMPOSITIONS
Peruvian Coastal
Batholith
NON-GENETIC CLASSIFICATIONS
OF GRANITIC ROCKS
Chemistry-based
Mineralogy-based
COMPOSITE
EMPLACEMENT
OF “GRANITIC”
BATHOLITHS
Tends toward more felsic
compositions over time
Epizonal batholiths form mostly by
roof collapse (stoping) or
downdropping of the chamber floor
CRUSTAL ANATEXIS AT DIFFERENT CRUSTAL DEPTHS
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)
SiO2
K2O/Na2O
Type
M
46-70%
low
Ca, Sr
high
A/(C+N+K)*
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
87
Sr/86Sr
Misc
Petrogenesis
low
< 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
18
Sr/86Sr
SiO2
K2O/Na2O Ca, Sr A/(C+N+K)* Fe /Fe
Type
Cr, Ni  O
Misc
Petrogenesis
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.
Th, U
Infracrustal
A
high
low
var to
var
low
var
var
lowRb,
LIL/HFS
Anorogenic
rocks
peraluminous
hornblende
Mafic
to intermed.
 77%
high
peralkaline
high Fe/Mg
Stable
craton
magnetite
igneous
source
high Ga/Al
Rift zone
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
REMELTING OF SEDIMENTARY ROCKS
* molar Al2O3/(CaO+Na2O+K2O)
Data from White and Chappell (1983), Clarke (1992), Whalen (1985)
Dehydration Melting of Hydrous
Mineral-bearing Rocks
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)
GRANITES CREATED DURING CONTINENTCONTINENT COLLISION (OROGENESIS)
POST-
OROGENIC
GRANTOIDS
EXTENSIONAL
COLLAPSE
PostPenokean
granites
TECTONIC DISCRIMINATION DIAGRAMS
FOR GRANITOIDS
Figure 18.9. Examples of granitoid discrimination diagrams used by Pearce et al. (1984, J. Petrol., 25, 956-983) with the
granitoids of Table 18-2 plotted. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.