1. The Chemical Composition of the Solar System and the Earth

2. Two suggestions
Expertise comes from making all possible mistakes (Niels Bohr)
Nothing can be obtained in geochemistry without careful analytical work (C.J. Allegre)

3. Further readings W.M. White, Geochemistry. A on-line text book.
S.R. Taylor and S.M., The Continental Crust: Its Composition and Evolution. Blackwell, Oxford.
W.F. McDonough and S.Sun, The Composition of the Earth, Chemical Geology, 120:
Geochemical Earth Reference Model (GERM)

4. Why do we study element abundances?
Fundamental for any geochemical studies

5. Confusing terms
Abundance: for a large system, e.g., Cosmos, Sun, Moon, Earth, crust, regional crust
Content/concentration: for a smaller system, e.g., rocks, minerals, natural water.

6. Part 1 The Solar/Cosmic system

7. Sources for studies Meteorite Sun’s Photosphere Cosmic rays
Earth and moon

8. Classification of meteorites according to texture and chemical composition (White, 2001)

9. Relative abundance of major types of meteorite falls

11. Characteristics of chondrite groups
Carbonaceous chondrites are the most volatile-rich and the most primitive.

12. Condensation sequence of a gas with a solar composition

13. Condesation sequence of minerals

14. Goldschmidt’s classification of elements

15. Classification of elements (McDonough and Sun, 1995)

16. Classification of elements according to volatility

17. Ca-Al inclusion
There is much interest in high T component, i.e., the so-called Refractory Inclusions (RI) or Ca-Al inclusions (CAI), because their composition represents that of the first condensates from a high T gas.

18. Carton illustrating the process involved in formation of chondrites and their components

19. Abundances of elements in sun’s photosphere vs their abundances in CI chondrites (White, 2001)

20. Comparison of element abundances in solar photosphere and CI carbonaceous chondrites (Taylor and McLennan, 1995)

22. Solar system abundances of elements relative to Si=10-6

24. Characteristic of element abundances of the solar system
H and He accounts for 98% in mass.
Exponential decrease in abundance for elements with atomic number<45.
Elements with even mass show significantly higher abundances than the neighboring elements with odd mass.
He exhibit an abnomously high abundance compared to the neighboring Li, Be and B.
O and Fe show a peak.
Isotopes with atomic weight being factor of 4 have high abundance. 4He (Z=2, N=2), 16O (Z=8, N=8),
40Ca (Z=20, N=20).

25. Even-odd mass effect 58 60 66 64 70 57 68 62 59 63 67 65 71 69

26. Sequence of decreasing element abundances in the solar system
HHeOCN, NeMg, SiFeS
1010 to 109
107
106
105

27. Neocleosynthesis
The Big Bang

28. Steller structure at the onset of supernova stage (White, 2001)
The E-process (Si burning)
The S-process (neutron capture)
The r-process (Rapid neutron capture)
Principle mechanism for forming heavier isotopes
The p-process (Proton capture)
Responsible for the lightest isotopes of
a given element

29. The r-process path

30. Part 2 The Moon

31. Representative compositions of lunar rocks

32. Comparison of the composition of the Moon and the Earth

33. Highlights of lunar Geochronology

34. Part 3 The Earth

35. Volumes and masses of the Earth’s shells

36. The Earth’s Interior Mantle: Peridotite (ultramafic)
Upper to 410 km (olivine ® spinel)
Low Velocity Layer km
Transition Zone as velocity increases ~ rapidly
660 spinel ® perovskite-type
SiIV ® SiVI
Lower Mantle has more gradual velocity increase
Figure 1-2. Major subdivisions of the Earth. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

37. The Earth’s Interior Core: Fe-Ni metallic alloy Outer Core is liquid
No S-waves
Inner Core is solid
Figure 1-2. Major subdivisions of the Earth. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

38. Figure 1-3. Variation in P and S wave velocities with depth
Figure 1-3. Variation in P and S wave velocities with depth. Compositional subdivisions of the Earth are on the left, rheological subdivisions on the right. After Kearey and Vine (1990), Global Tectonics. © Blackwell Scientific. Oxford.

39. Part 3-1 The mantle

40. Methods of studies Mantle xenoliths entrained by volcanic rocks
Massif peridotite: Exhumed mantle slab
Mantle-derived volcanic rocks
Experiments at high P-T
Seismic and density properties

41. Mantle Rock Types

42. Rock Names
Peridotite: ultramafic rock composed of olivine, 2 pyroxenes (opx-cpx) and Al-phase (i.e., plagioclase, spinel, garnet, with the specific phase being a function of pressure, 0-10, 10-25, >25 Kb respectively), includes: lherzolite, harzburgite, dunite

43. Eclogite: mafic (i.e., basaltic) rock composed of Na-rich clinopyroxene and garnet

44. Pyroxenite: mafic to ultramafic rock, dominantly composed of pyroxene, often containing an Al-phase (e.g., plagioclase, spinel, garnet)

45. Non-Rock Names
Primitive Mantle/Silicate Earth: model composition for the crust + mantle.
Pyrolite: model composition for the primitive mantle, name derived from pyroxene-olivine-ite.
Piclogite: model composition for the mantle, name derived from picritic-eclogite (picrite = olivine-rich basalt).

46. Lherzolite: A type of peridotite with Olivine > Opx + Cpx
Dunite 90
Peridotites
Wehrlite
Harzburgite
Lherzolite 40
Olivine Websterite
Pyroxenites
Orthopyroxenite 10
Websterite 10
Clinopyroxenite
Orthopyroxene
Clinopyroxene
Figure 2-2 C After IUGS

47. Mantle rock mineral assemblage
Simple: 4 or 5 phases
Olivine (Ol)
Orthopyroxene (OPX)
Clinopyroxene (CPX)
Plagioclase (Pl)
Spinel (Sp)
Garnet (Gt)

48. Composition of rocks Pyrolite harzburgite lherzolite eclogite SiO2 4546 44 50
Al2O3
4.5
1.2
2.2 16
FeO
8.0
7.3
8.2 10
MgO 38 41 8
CaO
3.6
0.9
*Mg#
89.4
91.5
89.9
58.8
*density r
3.385
3.346
3.376
3.970
olivine 56 62 65 --
orthopyx 18 30 21
clinopyx 2
garnet 14 6

49. Modal and physical property for lithospheric mantle of different ages (After O’Reilly et al., 2001)

50. Mantle Phase Diagrams

51. Phase diagram for aluminous 4-phase lherzolite:
Al-phase =
Plagioclase
shallow (< 50 km)
Spinel
50-80 km
Garnet km
Si ® VI coord.
> 400 km
Note: the mantle will not melt under normal ocean geotherm!
Figure Phase diagram of aluminous lherzolite with melting interval (gray), sub-solidus reactions, and geothermal gradient. After Wyllie, P. J. (1981). Geol. Rundsch. 70,

52. Mantle phase diagram

53. Phase assemblages and 1 atm density

54. Melting of Mantle
Melt: Basalt
Residue: Peridotite

55. Lherzolite is probably fertile unaltered mantle
Dunite and harzburgite are refractory residuum after basalt has been extracted by partial melting 15
Tholeiitic basalt 10
Partial Melting
Wt.% Al2O3 5
Figure 10-1 Brown and Mussett, A. E. (1993), The Inaccessible Earth: An Integrated View of Its Structure and Composition. Chapman & Hall/Kluwer.
Lherzolite
Harzburgite
Residuum
Dunite
0.0
0.2
0.4
0.6
0.8
Wt.% TiO2

56. How does the mantle melt??
1) Increase the temperature
No realistic mechanism for the general case
Local hot spots OK
very limited area
Figure Melting by raising the temperature.

57. 2) Lower the pressure
Adiabatic rise of mantle with no conductive heat loss
Decompression melting could melt at least 30%
Adiabatic rise of mantle with no conductive heat loss
Steeper than solidus
Intersects solidus
D slope = heat of fusion as mantle melts
Decompression melting could melt at least 30%
Figure Melting by (adiabatic) pressure reduction. Melting begins when the adiabat crosses the solidus and traverses the shaded melting interval. Dashed lines represent approximate % melting.

58. 3) Add volatiles (especially H2O)
Remember solid + water = liq(aq) and LeChatelier
Dramatic lowering of melting point of peridotite
Figure Dry peridotite solidus compared to several experiments on H2O-saturated peridotites.

59. Experiments on melting enriched vs. depleted mantle samples:
Tholeiite easily created
by 10-30% PM
More silica saturated
at lower P
Grades toward alkalic
at higher P
Figure 10-17a. Results of partial melting experiments on depleted lherzolites. Dashed lines are contours representing percent partial melt produced. Strongly curved lines are contours of the normative olivine content of the melt. “Opx out” and “Cpx out” represent the degree of melting at which these phases are completely consumed in the melt. After Jaques and Green (1980). Contrib. Mineral. Petrol., 73,

60. Experiments on melting enriched vs. depleted mantle samples:
2. Enriched Mantle
Tholeiites extend to
higher P than for DM
Alkaline basalt field
at higher P yet
And lower % PM
Figure 10-17b. Results of partial melting experiments on fertile lherzolites. Dashed lines are contours representing percent partial melt produced. Strongly curved lines are contours of the normative olivine content of the melt. “Opx out” and “Cpx out” represent the degree of melting at which these phases are completely consumed in the melt. The shaded area represents the conditions required for the generation of alkaline basaltic magmas. After Jaques and Green (1980). Contrib. Mineral. Petrol., 73,

62. Melting of mantle
T,P

63. CaO-Al2O3 plot showing the range of mantle composition of different ages (O’Reilly et al., 2001)
DEPLETION

64. Lherozlite from
Hannuoba,
North China Craton

65. Deepest mantle samples from transition zone: Majorite-Bearing Xenoliths from Malaita,Ontong Java Oceanic Plateau- 9.5 GPa (260 km) to 22 GPa (570 km).
Collerson et al., 2000, Science, 288:

66. Estimating pressure of garnet and majorite

67. Mantle phase diagram

68. Common lherzolite xenoliths come from a depth of 50-80 km: lithosphere

69. Phase diagram for aluminous 4-phase lherzolite:
Al-phase =
Plagioclase
shallow (< 50 km)
Spinel
50-80 km
Garnet km
Si ® VI coord.
> 400 km
Note: the mantle will not melt under normal ocean geotherm!
Figure Phase diagram of aluminous lherzolite with melting interval (gray), sub-solidus reactions, and geothermal gradient. After Wyllie, P. J. (1981). Geol. Rundsch. 70,

70. Structure of lithosphere
Nyblade, 2001

71. Lithosphere evolution in eastern North China craton (After O’Reilly et al., 2001)

72. Estimation of Primitive Mantle Composition

73. Mantle model circa 1975
Homogeneous mantle
Large-scale convection (drives plate tectonics?)
Figure 10-16a After Basaltic Volcanism Study Project (1981). Lunar and Planetary Institute.

74. Newer mantle model Upper depleted mantle = MORB+ crust sources
Lower undepleted & enriched OIB source
Layered mantle
Upper depleted mantle = MORB source
depleted by MORB extraction > 1 Ga
Lower = undepleted & enriched OIB source
Boundary = 670 km phase transition
Sufficient D density to impede convection so they convect independently
It is interesting to note that this concept of a layered mantle was initiated by the REE concentrations of oceanic basalts
Later support came from isotopes and geophysics
Figure 10-16b After Basaltic Volcanism Study Project (1981). Lunar and Planetary Institute.

76. Primitive vs metasomatism
Primitive: Flat REE
Metasomatism: LREE enriched

77. REE distribution of peridotite showing effect of mantle metasomatismz b g S p P m v 1 2 - L N d E T D y H Y
Chondrite normalization

78. Criteria for estimating Primitive Mantle Composition
Should have refractory lithophile element ratios that are similar to CI chondrite.

79. Variations with MgO in peridotite

80. Constant refractory element ratios in peridotites

81. Elemental ratios in chondritic meteorites (McDonough and Sun, 1995)

82. Variation of refractory lithophile element ratios in peridotites (McDonough and Sun, 1995)

83. Estimating refractory lithophile elements in bulk silicate Earth (McDonough and Sun, 1995)

84. Estimates of Silicate Earth -Major elements

85. Estimates of
Silicate Earth -Trace elements

86. Abundances of elements in Primitive mantle compared to CI condrites

87. Part 3-2 The Core and Bulk Earth

88. The Earth’s Interior Core: Fe-Ni metallic alloy Outer Core is liquid
No S-waves
Inner Core is solid
Figure 1-2. Major subdivisions of the Earth. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

89. Composition of the Core
Poorly constrained beyond its major constituents (i.e., an Fe-Ni alloy).
Presence of 5-15% of light element(s) (S, O, Si).
The dominant depository of siderophile elements in the Earth.

90. Limits on the compositions of the core and bulk Earth (McDonough & Sun, 1995)

91. Liquid silicate-liquid metal partition coefficients

92. Comparison of element distributions in the Earth and carbonaceous chondrites
The Earth is more strongly depleted in volatile elements

93. Figure 1-5. Relative atomic abundances of the seven most common elements that comprise 97% of the Earth's mass. An Introduction to Igneous and Metamorphic Petrology, by John Winter , Prentice Hall.

94. Part 3-3 The Oceanic crust

95. The Earth’s Crust Oceanic crust Continental Crust Thin: 10 km
Relatively uniform stratigraphy
= ophiolite suite:
Sediments
pillow basalt
sheeted dikes
more massive gabbro
ultramafic (mantle)
Continental Crust
Thicker: km average ~35 km
Highly variable composition
Average ~ granodiorite

96. Methods of study
Ophiolite
Ocean drilling
Seismic studies

97. Structure of oceanic crust

98. Plate Tectonics – Igneous Genesis
1. Mid-ocean Ridges
2. Intracontinental Rifts
3. Island Arcs
4. Active Continental
Margins
5. Back-arc Basins
6. Ocean Island Basalts
7. Miscellaneous Intra- Continental Activity
kimberlites, carbonatites, anorthosites...

99. Composition of the Oceanic Crust (Taylor and McLennan, 1995)

100. Part 3-4 The Continental crust
The continental crust accounts for 41% of the Earth surface.
Approximately 31% of continental area is submerged beneath the oceans.

101. Importance of Determining Crustal Composition
Basic constraints on evolution of the Earth.
Most accessible part of the Earth and the best known.
Place for formation of most of ore deposits.
Important depository for highly incompatible elements (U, K, Cs).
Essential for environmental studies and geochemical exploration.

102. Study of the composition of the continental crust can be traced back to earliest stage of geochemical studies
F.M.Clarke, 1889
F.M.Clarke and H.S.Washington, 1924
V.M.Goldschmidt,1933, who is regarded as the father of modern geochemistry.
S.R.Taylor, 1994
D.M.Shaw, 1967
S.R.Taylor and S.M. McLennan, 1985
K.H.Wedepohl, 1992

103. What is the Continental Crust ?
Extends vertically from the surface to the Mohorovicic discontinuity, a jump in compressional wave Vp speeds from ~7 km/s to ~8 km/s that is interpreted to mark the crust-mantle boundary.
Stratification in seismic velocity and thus rock type and chemical composition.
Lateral and vertically heterogeneous and great diversity in rock type.

104. Structure and compositional model of the continental crust (Wedepohl, 1995)

105. Metamorphic Facies Lower Crust Middle Crust Upper crust
Fig Temperature-pressure diagram showing the generally accepted limits of the various facies used in this text. Boundaries are approximate and gradational. The “typical” or average continental geotherm is from Brown and Mussett (1993). Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Middle Crust
The boundaries between metamorphic facies represent T-P conditions in which key minerals in mafic rocks are either added or removed, thus changing the mineral assemblages observed
They are thus separated by mineral reaction isograds
The limits are approximate and gradational, because the reactions vary with rock composition and the nature and composition of the fluid phase
The 30oC/km geothermal gradient is an example of an elevated orogenic geothermal gradient.
Upper crust

106. Part 3-4-1 The Upper Continental Crust : the most accessible part of the Earth

107. Methods of Studies
Large-scale regional sampling (e.g., the Canadian Shield)
Using fine-grained clastic sediments

108. Large-scale regional sampling
Examples: The Canadian Shield and Eastern China.
The most reliable method for upper crustal composition estimation.
The only method for major element composition studies.
Expensive and time-consuming.
Not pertain to the study of upper crustal composition in the geological history.

109. Sampling in Eastern China

111. Fine-Grained Clastic Sediments as Natural Sampling of the Exposed Upper Continental Crust
Shale, mudstone, siltstone, graywack, tillite, and loess.
Simple and much less expensive.
The only way for studying upper crustal composition in geological history.
Unsuitable to providing the major element composition.
Limited to REE, Y, Th, Sc, Co.

112. Geological influences on sedimentary rock composition-Solubility
Water-upper crust partition coefficient:
Ky=Natural water/Upper crust
Seawater residence time y: time for replacement of seawater element concentration.
y=My/Fy
where My is the mass of element y in the oceans and Fy is the annual mean flux of element y through the ocean reservoir.

113. Residence time vs seawater partition coefficients

114. Weathering Ca, Na and Sr are lost K, Rb, Cs and Ba are retained.
Al, Ga, HSFE (Ti, Zr, Hf, Ta, Th) and REE, Y, Sc are immobile.

115. CIA: Chemical Index of Alteration CIA=Al2O3/(Al2O3+CaO
CIA: Chemical Index of Alteration CIA=Al2O3/(Al2O3+CaO*+Na2O+K2O) in molecular proportion
Plagioclase is the dominant phase in the continental crust subjected to weathering.

117. Erosion and transportation
The sand-size effect.
Quartz and heavy minerals (zircon, rutile, magnetite, chromite) are enriched in sandstone.

118. Diagenesis Sensitive to redox conditions
Fe and Mn are soluble in anoxic conditions.
Fe, Cu, Mo, Pb, Zn, V, Ni, S, C are clearly enriched in anoxic sediments due to incorporation in sulphides and/or absorption on organic compounds.
U is enriched also in anoxic sediments due to reduction of soluble 6+U to insoluble 4+U.

119. Metamorphism Poorly understood. Li and Pb may increase.
Most elements and particularly REE, Y, Th, HFSE, Cr and Sc are immobile.

120. Sedimentary rocks as crustal samples
Insoluble elements (log 4; Ksw -4) are likely to be transferred almost quantitatively into clastic sediments and give the best information regarding the source-exposed upper crust.

121. Quantitatively transferred into fine-grained clastic sediments
REE in fine-grained sediments provide quantitative info on the upper crust composition
Quantitatively transferred into
fine-grained clastic sediments

122. REE comparison of shales and upper crust

123. Constant element ratios in the upper crust

127. Estimation of upper crustal composition
Major elements:
large-scale sampling
Trace elements:
 large-scale sampling
 fine-grained clastic sediments
using REE and their ratios to
other elements

128. Various upper crustal major element estimates
Taylor & McLennan
Shaw et al.
Wedepohl
Condie
Gao et al.
Rudnick & Gao
1985
1967
1995
1993
1998
2002
SiO2 66
64.93
66.21
65.46
65.84
TiO2
0.5
0.52
0.55
0.65
0.60
Al2O3
15.2
14.63
14.96
13.65
14.31
FeOT
4.50
3.97
4.70
5.13
4.92
MnO
0.07
0.068
0.1
0.10
MgO
2.2
2.24
2.42
2.52
2.47
CaO
4.2
4.12
3.6
3.31
3.46
Na2O
3.9
3.51
2.75
3.13
K2O
3.4
3.1
2.73
2.58
2.66
H2O
0.79
2.11
P2O5
0.2
0.15
0.12
0.14
Total
100.17
97.98
98.80
98.41
99.71

129. Upper crustal compositional estimates (Taylor and McLennan, 1985)

130. Comparison of loess and upper crustal compositions (Taylor and McLennan, 1985)

131. Part The deep crust

132. Methods of Studies
Amphibolite- and granulite-facies xenoliths entrained mostly in basalts.
Exposed deep crustal sections
Correlation of seismic velocities of rocks with lithologies
Heat flow constraints

133. Crustal structure based on deep crusal xenoliths (Mengel et al., 1992)

134. Deep Crustal Xenoliths
Mostly granulite-facies

135. Histogram of SiO2 in granulite xenoliths
(Rudnick, 1992)

136. Exposed Deep Crustal Section

137. Model for exposed deep crustal cross-section (Percival and Fountain, 1992)

138. P-wave and Poisson’s ratio structure along the exposed Kapuskasing deep crustal section (Percival and Fountain, 1994)
P-wave velocity (km)
Poisson’s ratio

139. Contrasts between granulite xenoliths and terrain granulites
麻 粒 岩 地 体
麻 粒 岩 包 体
时 代
太古－ 元古宙
后太古宙
压 力
MPa
MPa
深 度
25-35 km
35-50 km
岩 性
中性和长英质为主
镁铁质－超镁铁质为主
SiO2
55-75%
40-55%

140. Correlation of seismic velocities with rock types
Compressional P-wave velocity (Vp)
Shear S-wave velocity (Vs)
Poisson’s ratio ()
=0.5{1 – 1/[(Vp/Vs)2 – 1]}

141. Measurement of seismic velocities of rocks

142. Calculation of velocities in depth
V(z)=V(0) + [(dV/dP)T P + (dV/dT)PT]dz
Where V(0) and V(z) are velcities at a reference state and at depth z.
For common rocks, (dV/dP)T =210-4 to 710-4 km s-1 MPa-1; (dV/dT)P = -210-4 to -610-4 km s-1 C-1

143. Effect of heat flow on Vp (Rudnick and Fountain, 1995)

144. 150 MPa 下侵入岩Vp随成分的变化 (Fountain and Christensen, 1989)

145. Relation between SiO2 and Vp of granulites (Rudnick and Fountain, 1995)

146. Density vs Vp
Peridotite
Eclogite
Mafic granulite

147. 1、蛇纹岩
2、石英岩
3、花岗岩
4、花岗闪长岩
5、角闪岩相长英质片麻岩
6、石英云母片岩
7、绿片岩相变辉长岩
8、辉长岩
9、斜长角闪岩
1、长英质角闪片麻岩
2、长英质片麻岩
3、中性麻粒岩
4、斜长岩
5、镁铁质麻粒岩
6、斜长角闪岩
7、麻粒岩相变泥质岩
8、辉石岩
9、榴辉岩
10、纯橄榄岩/二辉橄榄岩
Holbrook et al. (1992)

148. Crustal structure in various tectonic settings (Rudnick and Fountain, 1995)

149. Normative mineral composition of continental crust (Taylor and McLennan, 1995)

151. Comparison of upper, middle and lower crust compositions (Rudnick and Fountain, 1995)

152. Relation between Continental Crust and MORB

154. Comparison of various REE and trace element estimates of continental crust (Rudnick and Fountain, 1995)

155. Comparison of continental crust and various basalts (Hoffmann, 1994)

156. Compositional characteristics of continental crust
The upper crust is granitic with 66% SiO2 and with a significant negative Eu anomaly.
The middle crust is tonalitic with 61% SiO2.
The lower crust is mafic in many regions with ~52% SiO2 and may be more evolved for some cratons (e.g., North China Craton) and collision belts.
Relative depletion in Nb and enrichment in Pb characterize the continental crust and continental crustal rocks- “the arc signature”.
The total continental crust has an andesitic/granodioritic bulk composition with 59-62%. It contains a significant proportion of the bulk silicate Earth’s incompatible element budget (33-35% of Rb, Ba, K, Pb, Th and U).

157. Schematic model for growth and evolution of the continental crust (Taylor and McLennan, 1995)

158. Total Continental CrustLa Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 1 10
100
Rock/Chondrite
East China (this study; Eu/Eu*=0.80)
Wedepohl (1995; Eu/Eu*=0.83)
Rudnick & Fountain (1995; Eu/Eu*=0.98)
Taylor & McLennan (1995; Eu/Eu*=1.00)
Total Continental Crust

159. Relative Vp change with depth under varying surface heat flows

160. Contrasting lower crustal velocities for Archean and Proterozoic provinces (Durrheim and Mooney, 1991)

161. The following slides are not used in the lectures

162. Generation of tholeiitic and alkaline basalts from a chemically uniform mantle
Variables (other than X)
Temperature
Pressure
Variables (other than X)
Temperature
= % partial melting
Pressure
Fig indicates that, although the chemistry may be the same, the mineralogy varies
Pressure effects on eutectic shift
Figure Phase diagram of aluminous lherzolite with melting interval (gray), sub-solidus reactions, and geothermal gradient. After Wyllie, P. J. (1981). Geol. Rundsch. 70,

163. Liquids and residuum of melted pyrolite
Tholeiite produced at < 30 km depth by 25% PM
60 km
Alkalis are incompatible so tend to concentrate in first low % partial melts
20% PM -> alkaline basalt
30% PM -> tholeiite (only 25% or less at 30 km so looks like tholeiitic nature suppressed with depth)
Note that residuum is Ol + Opx (harzburgite)
Note also the thermal divide between thol and alk at low pressure for FX
Figure 10-9 After Green and Ringwood (1967). Earth Planet. Sci. Lett. 2,

164. Initial Conclusions: Tholeiites favored by shallower melting
25% melting at <30 km ® tholeiite
25% melting at 60 km ® olivine basalt
Tholeiites favored by greater % partial melting
20 % melting at 60 km ® alkaline basalt
incompatibles (alkalis) ® initial melts
30 % melting at 60 km ® tholeiite

165. Crystal Fractionation of magmas as they rise
Tholeiite ® alkaline
by FX at med to high P
Not at low P
Thermal divide
Al in pyroxenes at Hi P
Low-P FX ® hi-Al
shallow magmas
(“hi-Al” basalt)
Figure Schematic representation of the fractional crystallization scheme of Green and Ringwood (1967) and Green (1969). After Wyllie (1971). The Dynamic Earth: Textbook in Geosciences. John Wiley & Sons.

166. Primary magmas
Formed at depth and not subsequently modified by FX or Assimilation
Criteria
Highest Mg# (100Mg/(Mg+Fe)) really ® parental magma
Experimental results of lherzolite melts
Mg# = 66-75
Cr > 1000 ppm
Ni > ppm
Multiply saturated

167. Summary
A chemically homogeneous mantle can yield a variety of basalt types
Alkaline basalts are favored over tholeiites by deeper melting and by low % PM
Fractionation at moderate to high depths can also create alkaline basalts from tholeiites
At low P there is a thermal divide that separates the two series
In spite of this initial success, there is evidence to suggest that such a simple approach is not realistic, and that the mantle is chemically heterogeneous

168. REE data for oceanic basalts
Ocean Island Basalt (Hawaiian alkaline basalt)
Looks like partial melt of ~ typical mantle
Mid Ocean Ridge Basalt (tholeiite)
How get (+) slope??
increasing incompatibility
Figure 10-13a. REE diagram for a typical alkaline ocean island basalt (OIB) and tholeiitic mid-ocean ridge basalt (MORB). From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. Data from Sun and McDonough (1989).

169. Spider diagram for oceanic basalts
Same approach for larger variety of elements
Still OIB looks like partial melt of ~ typical mantle
MORB still has (+) slope
Looks like two mantle reservoirs
MORB source is depleted by melt extraction
OIB source is not depleted
is it enriched?
increasing incompatibility
Figure 10-13b. Spider diagram for a typical alkaline ocean island basalt (OIB) and tholeiitic mid-ocean ridge basalt (MORB). From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. Data from Sun and McDonough (1989).

170. REE data for UM xenoliths
LREE enriched
LREE depleted
or unfractionated
REE data for UM xenoliths
LREE depleted
or unfractionated
LREE enriched
Depleted types (+) slope
Fertile types (-) slope
Enriched?
Figure Chondrite-normalized REE diagrams for spinel (a) and garnet (b) lherzolites. After Basaltic Volcanism Study Project (1981). Lunar and Planetary Institute.

171. Cross-section of a subduction zone

172. 俯冲板片的熔融和大陆地壳的形成
Whinter (2001)

173. The Geothermal Gradient
Continental Gradient higher than Oceanic Gradient
Range for both
Highest at Surface
water and cold surface
In the future we will often use average values rather than the ranges
Figure 1-9. Estimated ranges of oceanic and continental steady-state geotherms to a depth of 100 km using upper and lower limits based on heat flows measured near the surface. After Sclater et al. (1980), Earth. Rev. Geophys. Space Sci., 18,

174. Fig Temperature- pressure diagram showing the three major types of metamorphic facies series proposed by Miyashiro (1973, 1994). Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
The high P/T series, for example, typically occurs in subduction zones where “normal” isotherms are depressed by the subduction of cool lithosphere faster than it can equilibrate thermally
The facies sequence here is (zeolite facies) - (prehnite- pumpellyite facies) - blueschist facies - eclogite facies.
The medium P/T series is characteristic of common orogenic belts (Barrovian type)
The sequence is (zeolite facies) - (prehnite-pumpellyite facies) - greenschist facies -amphibolite facies - (granulite facies)
Crustal melting under water-saturated conditions occurs in the upper amphibolite facies (the solidus is indicated in Fig. 25-2)
The granulite facies, therefore, occurs only in water-deficient rocks, either dehydrated lower crust, or areas with high XCO2 in the fluid

177. Earth’s earliest history (in Ma)

178. Upper mantle phase diagram

179. Craton vs off-craton differences

180. Craton vs off- craton differences

181. Craton vs off- craton differences

182. Craton vs off- craton differences

183. Craton vs off-craton differences

184. Heat flow constrains

185. Heat flow structure

186. Incompatible lithophile element distributions caused by removal of basaltic melt from primitive mantle (Carlson, 1994)

187. REE comparison of various shales and upper crustal estimates

188. SiO2 distribution in granulites Rudnick and Fountain (1995)

189. Comparison of present and paleo-position of exposed crustal sections (Fountain et al., 1990)

190. Average Poisson’s ratio vs SiO2 for major rock types (Christensen, 1996)

191. 0 km 14 km 24 km 32 km 37 km Bulk Lower Crust Total Crust Vp=6.9 km/s
UPPER
CRUST
MIDDLE
LOWER
LOWERMOST
14 km
24 km
32 km
37 km
0 km
Sedimentary and Volcanic Rocks
Granitoids
Low-grade Metamorphic Rocks
Vp=6.4 km/s
SiO2=62%
90% TTGG gneiss
10% Amphibolite
Vp=6.7 km/s
SiO2=58%
100% intermediate granulite
or 75% felsic+25%mafic granulite
Vp=7.1 km/s, SiO2=52%
Mafic granulite
Bulk Lower Crust
53% Mafic granulite
47% Felsic granulite
Vp=6.9 km/s
SiO2=55-57% (52%, 7.14 km/s; R & F, 1995)
Vp=6.0 km/s
SiO2=65%
Total Crust
SiO2=62-64% (59%, 6.67 km/s; R & F, 1995)

192. Comparison of Sr-Nd isotopic composition of basalts (Hofmann, 1994)

193. REE mobility in weathering profile

195. REE distributions of heavy minerals

196. Effect of zircon addition

197. Effect of allanite addition

198. Effect of monazite addition

199. Interpretation of sedimentary Nd model ages in terms of sedimentary recyling

200. Nd vs Th/Sc for various modern sediments

201. Models for origin of plumes (Hofmann, 1994)

203. REE patterns for selected modern sediments

204. Effect of zircon enrichment

205. REE patterns of modern and Phanerozoic turbidites

206. Moder turbidite muds and Australian shales

207. Early Proterzoic sedimentary rocks from northern New Mexico and southern Corolado

209. REE pattern of seawater

210. Ce/Ce* variation of seawter and clastic sediments with tectonic setting

211. Chemical variation of sediments from spreading ridge

212. Variation of REE patterns with stratigraphic order

213. Variation of REE from ridge

216. Tectonic map of China (李献华)

217. （据李献华）

218. 扬子克拉通南缘沉积岩Nd随时代的变化（李献华）

223. Effect of monazite addition

224. Diagenetic chemical fractionation during formation of chert

228. REE patterns of Eu-enriched turbidite sandstone