Download LECTURE W9-L25-26 - Granites and Collisions

Igneous petrology
Part II – Important igneous
associations
• Granites (and convergence/collision)
• Ophiolites (oceanic crust) and MORB
(Mid-ocean ridge basalts)
• Layered igneous complexes (intra-plate,
economic importance)
• Oceanic island basalts (OIB) (intraplate)
• Continental alkali series (intraplate)
• Andesites (active subductions)
• Continental arcs (active subductions)
• TTG (Archaean)
• Komatiites (Archaean)
Granites and collisions
Exemple of the Himalaya
• Granites are typically associated to
convergent plate boundaries
• Different types form at different moments
of the convergence
• Example of an active collision zone : the
Himalaya
Subducting oceanic
lithosphere deforms
sediment at edge of
continental plate
Collision – welding
together of continental
crust
Post-collision: two
continental plates are
welded together, mountain
stands where once was
ocean
Rifting of continental crust to form a new ocean basin
The Himalayas: geodynamic
context
• India-Eurasia convergence
• Destruction of the Tethys ocean
• Subduction stage (> 100 Ma – 25 Ma =
Cretaceous-Oligocene)
• Collision stage (25 Ma – present =
Miocene and Pliocene)
• Post-collision stage (present)
Himalayan collision
5 cm/an
10 cm/an
18 cm/an
Remontée
de
l ’Inde
et collision
à
55 Ma
C. 70 Ma
30°
M
ak
ra
n
Asian Margin
O
m
KohistanLadakh
an
F u tu
Arabia
0°
re IT
SZ
Tibet
W
S.L.
F
Fr u t u r
ac e
tu O w
re e
zo n
ne
Africa
S.T.
?
30°
India
Intra-oceanic arc
Active continental
margin
The subduction stage
Les témoins de la subduction de l ’Inde sous l ’Asie
Zanskar
Indian crust
MHT
The
Les témoins de la
collisioncollision
stagecontinentale
Std
Ky
Bt
Mu
Zanskar
Indian crust
MHT
400
T°C
500
700
600
2
4
L
50 Ma
M2
18-25 Ma
6
8
M1
10
45 Ma
37-32 Ma
SSW
NNE
Spontang
Tethys -Himalaya
MHT
Higher Himalaya
Tibet
Ladakh
Moho
55 Ma
N
eo
t
eth
Shikar Beh
Higher Himalaya
Tethys -Himalaya
MHT
Ladakh
Tibet
50 Ma
55-40 Ma : > 400 km > 2.6 cm/y
Sub-Himalaya
Tethys -Himalaya
Lesser Himalaya
Ladakh
Higher Himalaya
MHT
Tibet
40 Ma
ISZ
STDS
MCT
0
Sub-Himalaya
30
60
km
Less
er
H im
Tethys -Himalaya
alaya
Tibet
Moho
MHT
0
30
60km
40-20 Ma : ~ 360 km , ~ 1.8 cm/y
20 Ma
ys
Erosion
200
400
600
200°C
10
400
20
600
30
800
40
50
km
800
0
100
200 km
The « late to post » collision stage
Successive magmatic associations
(mostly granites!)
150
125
100
75
50
25
0
tps (Ma)
Subduction stage
• Trans-Himalayan batholith
• Cretaceous-Oligocene
• Similar to Andean or Cordileran
(California, British Columbia, Japan…)
plutons
• I-types (Andean)
Diorites
Tonalites
Granodiorites
Granites
Hornblende granodiorite
Hbl-Biotite granodiorite
Cpx
Hbl
Bt
Major elements
biotite
muscovite
cordierite
andalusite
garnet
pyroxene
hornblende
biotite
aegirine
riebeckite
arfvedsonite
CaO
CaO
moles
CaO
K2O
K2O
Al2O3
K2O
Na2O
Peraluminous
Al2O3
Al2O3
Na2O
Metaluminous
Na2O
Peralkaline
Figure 18-2. Alumina saturation classes based on the molar proportions of Al2O3/(CaO+Na2O+K2O) (“A/CNK”) after Shand (1927).
Common non-quartzo-feldspathic minerals for each type are included. After Clarke (1992). Granitoid Rocks. Chapman Hall.
Chapter 18: Granitoid Rocks
Table 18-3. The S-I-A-M Classification of Granitoids
SiO2
K2O/Na2O
Type
M
46-70%
low
Ca, Sr
high
I
53-76%
low
high in
mafic
rocks
S
65-74%
high
low
A/(C+N+K)*
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
low
< 9‰
low
high
> 9‰
var
low
var
low
low: metal- moderate
uminous to
peraluminous
high
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)
Trace elements
Isotopes
Mixed sources
(mantle +
some crust ?)
Origin
• Will be discussed during the
« subduction » lectures
Successive magmatic associations
(mostly granites!)
150
125
100
75
50
25
0
tps (Ma)
Collision stage
• High Himalaya leucogranites
• Miocene
• S-type
Granites
± Alk. Granites
± Granodiorites
2 micas granites
Tourmaline granite
Bt
Kfs
Ms
Pl
•
•
•
•
•
Biotite
Muscovite
Tourmaline
Garnet
(Cordierite)
Major elements
biotite
muscovite
cordierite
andalusite
garnet
pyroxene
hornblende
biotite
aegirine
riebeckite
arfvedsonite
CaO
CaO
moles
CaO
K2O
K2O
Al2O3
K2O
Na2O
Peraluminous
Al2O3
Al2O3
Na2O
Metaluminous
Na2O
Peralkaline
Figure 18-2. Alumina saturation classes based on the molar proportions of Al2O3/(CaO+Na2O+K2O) (“A/CNK”) after Shand (1927).
Common non-quartzo-feldspathic minerals for each type are included. After Clarke (1992). Granitoid Rocks. Chapman Hall.
Chapter 18: Granitoid Rocks
Table 18-3. The S-I-A-M Classification of Granitoids
SiO2
K2O/Na2O
Type
M
46-70%
low
Ca, Sr
high
I
53-76%
low
high in
mafic
rocks
S
65-74%
high
low
A/(C+N+K)*
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
low
< 9‰
low
high
> 9‰
var
low
var
low
low: metal- moderate
uminous to
peraluminous
high
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)
Trace elements
Isotopes
Very « crustal »
Origin
1. Lesser Himalaya
2. Formation I (Greywackes et métapélites)
3. Formation II (Gneiss calciques)
4. Formation III (Orthogneiss)
5. Sédiments tibétains
6. Leucogranite du Manaslu
7. Dykes
Dalle du Tibet
Les granites syncollisionels du Haut Himalaya
Migmatites de la formation I
Successive magmatic associations
(mostly granites!)
150
125
100
75
50
25
0
tps (Ma)
Late to post-collision stage
• Syenites and alkali granites
• Miocene to present
• A-type
• N.B. Some « sub-alkali », « Mg-K » I-types (cf.
Vredenburg pluton as seen in Paternoster) are
also emplaced at this stage
Le magmatisme « post-collisionel » himalayen
Cas du magmatisme Néogène du Sud Karakorum
Syenites
Qtz. Syenites
Granites
Alk. granites
Cpx, Fe-rich
Sometimes
Na-Cpx or
Amph
Little/no plag
(Riebeckite, Aegyrine
Ardfersonite)
Major elements
biotite
muscovite
cordierite
andalusite
garnet
pyroxene
hornblende
biotite
aegirine
riebeckite
arfvedsonite
CaO
CaO
moles
CaO
K2O
K2O
Al2O3
K2O
Na2O
Peraluminous
Al2O3
Al2O3
Na2O
Metaluminous
Na2O
Peralkaline
Figure 18-2. Alumina saturation classes based on the molar proportions of Al2O3/(CaO+Na2O+K2O) (“A/CNK”) after Shand (1927).
Common non-quartzo-feldspathic minerals for each type are included. After Clarke (1992). Granitoid Rocks. Chapman Hall.
Chapter 18: Granitoid Rocks
Table 18-3. The S-I-A-M Classification of Granitoids
SiO2
K2O/Na2O
Type
M
46-70%
low
Ca, Sr
high
I
53-76%
low
high in
mafic
rocks
S
65-74%
high
low
A/(C+N+K)*
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
low
< 9‰
low
high
> 9‰
var
low
var
low
low: metal- moderate
uminous to
peraluminous
high
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)
Trace elements
Isotopes
10 Asthénosphère
5
eNd
0
-5
Composite (mantle + crust),
with some mantle-derived
units and some crustal units
-10
-15
leucogranites
du Haut Himlaya, 20 Myr
-20
0.70 0.71 0.72 0.73 0.74 0.75 0.76 0.77
86Sr/87Sr
Sud Karakorum
Hemasil, 8 Myr
Hunza, 4 -25 Myr
Baltoro, 17-25 Myr
Sud Tibet, 10-16 Myr
Sud Tibet, 17 Myr
Sud Tibet, 18-23 Myr
Sud Tibet, 23 - 25 Myr
Origin
• Shear heating
• Slab breakoff
« Shear heating » ?
Chaleur de frottement
Karakorum
Kunlun
BALTORO
MKT
N
K2
HEMASIL
MMT
Lamprophyres
South Tibet
neogenous
magmatism
North Tibet
neogenous
magmatism
Himalaya
Tibetan plateau
MCT
200km
MBT
ITSZ
« Slab breakoff »
Conclusion (1): a succession of
granite types
• Subduction (pre-collision): I « andean »
• Syn-collision: S-type leucogranites
• Post-collision : A (and I « Mg-K »)
This is, of course, a very simplified view !
Conclusion (2): Types of granitoids
Table 18-3. The S-I-A-M Classification of Granitoids
SiO2
K2O/Na2O
Type
M
46-70%
low
Ca, Sr
high
I
53-76%
low
high in
mafic
rocks
S
65-74%
high
low
A/(C+N+K)*
low
Fe3+/Fe2+
Cr, Ni
low
18O
< 9‰
low
< 9‰
low
high
> 9‰
var
low
var
low
low: metal- moderate
uminous to
peraluminous
high
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)
More granie classification
Table 18-4. A Classification of Granitoid Rocks Based on Tectonic Setting. After Pitcher (1983) in K. J. Hsü (ed.), Mountain Building
Processes, Academic Press, London; Pitcher (1993), The Nature and Origin of Granite, Blackie, London; and Barbarin (1990) Geol.
Journal, 25, 227-238. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Table 18-4. A
Classification of
Granitoid Rocks Based
on Tectonic Setting.
After Pitcher (1983) in
K. J. Hsü (ed.),
Mountain Building
Processes, Academic
Press, London; Pitcher
(1993), The Nature and
Origin of Granite,
Blackie, London; and
Barbarin (1990) Geol.
Journal, 25, 227-238.
Winter (2001) An
Introduction to Igneous
and Metamorphic
Petrology. Prentice Hall.