Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology...
-
Upload
samantha-odonnell -
Category
Documents
-
view
213 -
download
0
Transcript of Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology...
![Page 1: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/1.jpg)
Models of Crust Models of Crust CompositionCompositionModels of Crust Models of Crust CompositionComposition
Roberta L. RudnickGeochemistry LaboratoryDepartment of GeologyUniversity of Maryland
Apollo 17 view of Earth
![Page 2: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/2.jpg)
Plate Plate tectonics tectonics gives rise to gives rise to two types of two types of crust: crust: oceanic and oceanic and continentalcontinental
Plate Plate tectonics tectonics gives rise to gives rise to two types of two types of crust: crust: oceanic and oceanic and continentalcontinental
![Page 3: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/3.jpg)
Oceanic Crust:
Young (on average 80 Ma, <200 Ma) ~7 km thickHigh density: ~3.0 g/cm3
Low standing (-4000 m)Composition: Basalt (SiO2 ~50 wt.%)
![Page 4: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/4.jpg)
Oceanic
Generation of the Earth’s Crust
Intrusion and differentiation of mantle-derived basalt
From Press & Siever
![Page 5: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/5.jpg)
Continental Crust:
Ancient (on average 2 Ga, <4 Ga) ~40 km thickLow density: ~2.7 g/cm3
High standing (+800 m)Compositionally stratifiedDiverse rock types Composition: Andesite (SiO2 ~60 wt.%)
![Page 6: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/6.jpg)
Generation of the Earth’s Crust
?Convergent margin processes?
Intraplate processes?
Continental
![Page 7: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/7.jpg)
Upper Crust
Lower Crust
http://www.ub.es/ggac/research/piris
![Page 8: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/8.jpg)
Shuttle view of granite Shuttle view of granite intruding metamorphic intruding metamorphic basement, northern basement, northern Chile.Chile.
Continental Continental crust:crust:
Lots of heterogeneity!
Every rock type known on Earth occurs in continental crust
![Page 9: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/9.jpg)
How is crust composition determined?
![Page 10: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/10.jpg)
1.Crustal growth scenarios (Taylor & McLennan, 1985)
2.Empirical models (Christensen & Mooney, 1995; Wedepohl, 1995, Rudnick & Fountain, 1995; Rudnick & Gao, 2003)
Models of Crust Composition
![Page 11: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/11.jpg)
25% “Andesite model”75% Archean crust
Archean crust: Mixture of Archean basalt & Archean granite*Assume 50% of 40 mWm-2 surface heat flow
derives from crust: 75% basalt, 25% granite
Taylor & McLennan Recipe
*A special type of granite called tonalite, with relatively low K, Th and U
![Page 12: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/12.jpg)
Upper crust: grid sampling & sedimentary rocks
Deep crust: determined from seismic velocities, heat flow
Empirical Models
![Page 13: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/13.jpg)
Upper crust major elements: Grid sampling
Space shuttle view of Thunder Bay, Ontario
![Page 14: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/14.jpg)
Upper continental crustis granitic (67 wt.% SiO2)
![Page 15: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/15.jpg)
Trace elements: analyses of sedimentary rocks
Quantitative transport of insoluble elements from site of weathering to deposition.
![Page 16: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/16.jpg)
log
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
SolubleModerately soluble
Insoluble
-10.0 -8.0 -6.0 -4.0 -2.0 0.0
Cu
Au
Mo
CaLi
Re Sr
K Mg
B
Na
WSb
SeRb
U
Cs
BiCd
As
SiV
Ag
Ni
BaTl
Fe
Mn
HfTa
GaIn
Ge
Zn
Cr
ThAl Sc Co
TiY
SnZr
Nb
PbBe
REE
log Kswy
Insoluble elements:
Transferred from source of weathering to sediments
After Taylor & McLennan, 1985
(residence time)
(sea water partition coefficient)
La (REE)
![Page 17: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/17.jpg)
r2 = 0.15
K2O
0.0
1.0
2.0
3.0
4.0
10 15 20 25 30 35 40
La (ppm)
2
4
6
8
10
12
14
10 15 20 25 30 35 40
Th
r2 = 0.82
101.0
1.5
2.0
2.5
3.0
3.5
15 20 25 30 35 40 45
U
r2 = 0.48
Rudnick & Gao, 2003
Taylor & McLennan, 1985
Gao et al., 1998
Loess: samples of averaged upper crust?
La (ppm)
![Page 18: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/18.jpg)
Upper crustal estimates: Major elements
0.6
0.8
1
1.2
1.4 Shaw et al.Eade & Fahrig
Taylor & McLennan
Nor
mal
ized
to U
CR
&G
0.6
0.8
1.0
1.2
1.4
Si Al Fe Mg Ca Na K
BorodinCondieGao et al.Ronov & Yaroshevsky
Nor
mal
ized
to U
CR
&G
Wt. % K2O:
2.7 to 3.4%
Rudnick & Gao: 2.8 wt.%
![Page 19: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/19.jpg)
Upper crustal estimates: U & Th
Th ppm:
8.6 to 10.8 (10.5)
U ppm:
1.5 to 2.8 (2.7)
Th/U = 3.9
0.5
1.0
1.5
Tl Pb Bi Th U
Actinides & heavy metals
Shaw
Gao et al.
Taylor & McLennan
Eade & Fahrig
Condie
![Page 20: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/20.jpg)
Granulite Facies Terrains
Granulite FaciesXenoliths
Deep Crustal Samples
Ross Taylor, KSZ, Ontario, 1983
![Page 21: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/21.jpg)
Shukrani Manya, Univ. Dar es Salaam, Tanzania
The great xenolith hunt
Profs. Gao and Wu, Shanxi, China
Bill McDonough, Queensland, Australia
![Page 22: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/22.jpg)
10
20
30
40
50
60
70
80
90
30 40 50 60 70 80 90
10
20
30
40
50
60
70
80
90
30 40 50 60 70 80 90
Mg#Mg#
Mg#Mg#
Granulite Facies Granulite Facies TerranesTerranes
ArcheanArchean Post-ArcheanPost-Archean
Lower crustal Lower crustal xenolithsxenoliths
SiOSiO22 (wt. %) (wt. %)
![Page 23: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/23.jpg)
Rifted MarginContractional Shield & Platform
Paleozoic OrogenRift
ExtensionalArc
Forearc0
20
40
60
KmVp
6.4 6.6 6.8 7.0 7.2
Middle and Lower Crust -- Seismic evidence
From Rudnick & Fountain, 1995
![Page 24: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/24.jpg)
22..66 22..88 33..00 33..22 33..44 33..66
66..00
66..55
77..00
77..55
88..00
88..55
Mafic rocks
Felsic rocks
Eclogites
m=21
m=22
Ultramafic rocks
VVpp
(m/s)(m/s)
Density (g/cmDensity (g/cm33))
Upper Mantle
Basalt
Granite
![Page 25: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/25.jpg)
No
r ma
liz
ed
to
R&
G
Weaver & Tarney
Shaw et al.
Gao et al.
Rudnick & Fountain
0.0
0.5
1.0
1.5
2.0
Si Al Fe Mg Ca Na K
Comparison of middle crustal models:Major elements
Wt. % K2O: 2.1 to 3.4%
Rudnick & Gao: 2.3 wt.%
![Page 26: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/26.jpg)
Th ULi Rb Cs Sr Ba Pb
0.5
1.0
1.5
2.0
Li Rb Cs Sr Ba Pb
2.6
Comparison of middle crustal models:Alkali, alkaline Earth & Actinides
Weaver & Tarney
Shaw et al.
Gao et al.
Rudnick & Fountain
Th ppm: 6.1 to 8.4 (6.5)
U ppm: 0.9 to 2.2 (1.3)
Th/U = 5.0
![Page 27: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/27.jpg)
No
rmal
ized
to
R&
F
0.0
0.5
1.0
1.5
2.0
Si Al Fe Mg Ca Na K
Weaver & Tarney
Shaw et al.
Gao et al.
Wedepohl
Taylor & McLennan
Terrains and models
Comparison of lower crustal models:Major elements
Wt. % K2O: 2.1 to 3.4%
Rudnick & Gao: 2.3 wt.%
![Page 28: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/28.jpg)
![Page 29: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/29.jpg)
Composition of the Continental Crust
Christensen Rudnick & Wedepohl Taylor & Rudnick && Mooney Fountain 1995 McLennan Gao, 2003
1995 1995 1985, 1995
SiO2 62.4 60.1 62.8 57.1 60.6Al2O3 14.9 16.1 15.4 15.9 15.9FeOT 6.9 6.7 5.7 9.1 6.7MgO 3.1 4.5 3.8 5.3 4.7CaO 5.8 6.5 5.6 7.4 6.4Na2O 3.6 3.3 3.3 3.1 3.1K2O 2.1 1.9 2.7 1.3* 1.8
Mg# 44.8 54.3 54.3 50.9 55.3
*Updated by McLennan and Taylor, 1996
![Page 30: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/30.jpg)
Rudnick & Clarke*Gao, 2003 1889
SiO 2 60.6 60.2TiO 2 0.7 0.6Al 2O 3 15.9 15.3FeO T 6.7 7.3MnO 0.10 0.10MgO 4.7 4.6CaO 6.4 5.5Na 2O 3.1 3.3K 2O 1.8 3.0P 2O 5 0.13 0.23
Mg# 55.3 53.0
*Clarke, Frank Wigglesworth, for whom the Clarke medal is named
F.W. Clarke, 1847-1931
Composition of the Continental Crust
![Page 31: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/31.jpg)
![Page 32: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/32.jpg)
![Page 33: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/33.jpg)
![Page 34: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/34.jpg)
![Page 35: Models of Crust Composition Roberta L. Rudnick Geochemistry Laboratory Department of Geology University of Maryland Appolo image of Earth Apollo 17 view.](https://reader034.fdocuments.in/reader034/viewer/2022051819/5513d0ad55034674748b4cba/html5/thumbnails/35.jpg)