Preface ........................................................ ix
Acknowledgements ............................................... xi
1. Introduction ................................................. 1
1.1. Rock genesis and its relationship to geosystems ......... 1
1.1.1. Sedimentary rocks and continental geology ........ 1
1.1.2. Basaltic rocks and plate tectonics ............... 2
1.1.3. 'Whence the granites' ............................ 2
1.2. Granites, migmatites and granite problems ............... 4
1.2.1. Definitions ...................................... 4
1.2.1.1. Granite ................................. 4
1.2.1.2. Migmatite: terminology and
classification .......................... 5
1.2.2. Granite magma intrusion and its problems ......... 9
2. Crustal melting: experiments and conditions ................. 15
2.1. Introduction ........................................... 15
2.2. Mineral melting ........................................ 16
2.2.1. Topology of melting ............................. 17
2.2.2. Muscovite dehydration melting ................... 17
2.2.3. Biotite dehydration melting ..................... 19
2.2.4. Hornblende dehydration melting .................. 20
2.2.5. Biotite and hornblende melting in granitic
rocks ............................................ 20
2.2.6. Other hydrous minerals .......................... 21
2.2.7. Suprasolidus decompression-dehydration
reactions ....................................... 23
2.3. Rock melting-experimental evidence ..................... 24
2.3.1. Melt compositions ............................... 24
2.3.2. Restite compositions ............................ 27
2.3.3. Rock solidi ..................................... 27
2.3.4. Melt fraction ................................... 27
2.3.5. Conclusion ...................................... 30
2.4. Structure and composition of the crust ................. 33
2.5. Water in the crust ..................................... 36
2.6. Crustal heat and partial melting ....................... 42
2.6.1. Introduction .................................... 42
2.6.2. Thickened crust ................................. 44
2.6.3. Burial of high-radiogenic rocks ................. 45
2.6.4. Shear heating ................................... 48
2.6.5. Extension and removal of lithospheric mantle .... 51
2.6.6. Intrusion of mafic magma ........................ 60
2.6.7. Crustal thinning and'diapiric'decompression ..... 62
3. In situ melting and intracrustal convection: granite magma
layers ...................................................... 67
3.1. Introduction ........................................... 67
3.1.1. Geophysical evidence for crustal melting ........ 67
3.1.1.1. Himalayas and Tibetan plateau .......... 67
3.1.1.2. The Andes .............................. 69
3.1.2. P-T conditions of granite, migmatite and
granulite formation .................................... 70
3.2. Crustal melting I: Initial melting and partial melt
layer .................................................. 72
3.2.1. Formation of a partial melt layer ............... 72
3.2.2. Development of a partial melt layer in
heterogeneous crust .................................... 75
3.3. Crustal melting II: Convection and formation of magma
layer .................................................. 80
3.3.1. Gravitational separation and formation of
magma layer ..................................... 80
3.3.2. Convection and development of magma layer ....... 80
3.3.3. Upward thickening of magma layer ................ 84
3.4. Compositional variation within magma layer ............. 85
3.5. Magma layer, granite layer and granite bodies .......... 85
3.6. MI fluctuation (remelting) and granite sequence ........ 87
3.7. Conclusion ............................................. 87
4. Geological evidence for in situ melting origin of granite
layers ...................................................... 91
4.1. Migmatite to granite ................................... 91
4.1.1. Thor-Odin dome, Canada .......................... 91
4.1.2. Broken Hill, Australia .......................... 92
4.1.3. Mt. Stafford, Australia ......................... 93
4.1.4. Trois Seigneurs massif, Pyrenees ................ 95
4.1.5. Velay Dome, France .............................. 95
4.1.6. Coastal migmatite-granite zone, SE China ........ 97
4.1.7. Cooma and Murrumbidgee, Australia ............... 97
4.1.8. Optica grey gneiss, Canada ..................... 103
4.2. Contact metamorphism .................................. 104
4.3. Xenoliths and mafic enclaves .......................... 104
4.4. Granite layer and granite exposures ................... 110
4.5. Fluctuation of MI and downward-younging granite
sequence .............................................. 113
5. Differentiation of magma layer: geochemical
considerations ............................................. 123
5.1. Introduction .......................................... 123
5.2. Compositional variation ............................... 123
5.3. Strontium isotopes .................................... 135
5.4. Oxygen isotopes ....................................... 138
5.5. Rare earth elements ................................... 142
5.6. Summary ............................................... 148
6. Mineralisation related to in situ granite formation ........ 149
6.1. Introduction .......................................... 149
6.2. Source of ore-forming elements ........................ 149
6.3. Formation and evolution of ore-bearing fluid .......... 152
6.4. Types of mineral deposits ............................. 158
6.4.1. Vein mineralisation ............................ 158
6.4.2. Disseminated mineralisation .................... 159
6.5. Age relations ......................................... 160
6.6. Temperature distribution .............................. 161
6.7. Formation and distribution of hydrothermal mineral
deposits .............................................. 162
6.7.1. Precipitation of ore-forming elements .......... 162
6.7.2. Oxygen isotope evidence ........................ 164
6.8. Mineralised depth horizons ............................ 166
6.9. Mineralisation during elevated crustal temperatures ... 168
6.10. Mineralisation during granite remelting ............... 174
6.10.1. Oxidation ..................................... 174
6.10.2. Uranium mineralisation ........................ 176
6.11. Patterns of element redistribution and element
fields ................................................ 182
6.12. Summary ............................................... 185
7. Heat source for crustal magma layers: tectonic models ...... 187
7.1. Introduction .......................................... 187
7.2. Crustal temperature disturbance related to plate
convergence ........................................... 187
7.3. Subduction and granite formation: western Pacific
continental margin .................................... 191
7.3.1. Introduction ................................... 191
7.3.2. Tectonic framework of SE China and granite
formation ...................................... 192
7.3.3. Tectonic model ................................. 196
7.3.4. Multiple melting (remelting) and granite
belts .......................................... 198
7.3.5. Summary ........................................ 200
7.4. Continental collision and granite formation:
Tethys Belt ........................................... 201
7.4.1. Tectonic framework and granite distribution
of Tibet plateau ............................... 201
7.4.2. Tectonic phases in relation to subduction and
collision ...................................... 202
7.4.3. Magma layers and plate convergence ............. 205
7.5. Concluding statement .................................. 205
8. Geological effects of crystallisation of a crustal
granite magma layer: SE China .............................. 207
8.1. Fault-block basins .................................... 207
8.1.1. Characteristics and distribution of Mesozoic
basins ......................................... 207
8.1.2. Basin formation ................................ 208
8.1.3. Origin of red beds ............................. 212
8.1.4. Summary ........................................ 217
8.2. Volcanism ............................................. 217
9. Material and element cycling of the continental crust and
summary .................................................... 223
9.1. Rock cycling of continental material .................. 223
9.2. Element cycling of the continental crust .............. 225
9.3. Overview .............................................. 226
References .................................................... 229
Appendix 1 Map of SE China showing provinces .................. 249
Appendix 2 Results of experimental rock melting ............... 251
Index ......................................................... 273
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