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Shock Compression of Earth Materials and Implications for

the Composition of the Earth's Deep Interior

地球物質の衝撃圧縮と地球深部の組成の推定に関する研究

Youjun Zhang

Department of Earth and Planetary Systems Science,

Graduate School of Science,

Hiroshima University

Content of the thesis

Main Contents .............................................................................................................. III

Acknowledgements ...................................................................................................... IV

Table of Contents ........................................................................................................... 1

Abstract .......................................................................................................................... 7

Chapter 1. Introduction ................................................................................................ 10

1.1 The structure and composition of the Earth's deep interior ............................ 10

1.1.1 The interior structure of the Earth and the seismic observations .......... 10

1.1.2 Mantle minerals .................................................................................... 12

1.1.3 The Earth's core ..................................................................................... 15

1.2 Shock wave compression techniques and theories ......................................... 17

1.2.1 Shock compression techniques ............................................................. 17

1.2.2 Basic relations of shock waves ............................................................. 19

References ............................................................................................................. 22

Chapter 2. Significance and current studies for hydrous magnesium silicates in Earth's

interior .......................................................................................................................... 25

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2.1 Introduction for hydrous magnesium silicates ................................................ 25

2.2 Current studies of serpentinite at high pressures ............................................ 27

2.3 The content of the first part for this thesis ...................................................... 29

Reference .............................................................................................................. 30

Chapter 3. Dynamic compression and decomposition of antigorite and geophysical

implications .................................................................................................................. 34

3.1 Starting material .............................................................................................. 34

3.2 Experiments and conditions ............................................................................ 35

3.3 Hugoniot and sound velocity of antigorite and evidence for sluggish

decomposition ....................................................................................................... 38

3.3.1 Hugoniot equation of state (EOS) ......................................................... 38

3.3.2 Sound velocity ...................................................................................... 44

3.3.3 Partial released and recompression states ............................................. 46

3.3.4 Shock temperature ................................................................................ 48

3.4 Discussion on the decomposition reaction of serpentine under shock

compression .......................................................................................................... 52

3.4.1 Hugoniot of the dense hydrous magnesium silicate-phase H ............... 52

3.4.2 Decomposition products of antigorite at high pressures ....................... 54

3.5 Conclusions and geophysical implications ..................................................... 60

References ............................................................................................................. 62

Chapter 4. Significance and current studies for light elements of the Earth's core ..... 66

4.1 Introduction for the Earth's core and light elements ....................................... 66

4.1.1 Introduction of the chemical composition of Earth's core .................... 66

4.1.2 Brief reviews of light element candidates of the core ........................... 67

4.2 Current studies of Fe-(Ni)-Si systems at high pressures and high temperatures

............................................................................................................................... 70

4.3 The content of the second part for this thesis ................................................. 77

References ............................................................................................................. 78

Chapter 5. Hugoniot density, sound velocity and melting behavior of Fe-Ni-Si system

and implications for the Earth's core composition ....................................................... 86

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5.1 Starting material and initial characterizations................................................. 86

5.2 Hugoniot equation of state measurements ...................................................... 88

5.2.1 Experimental setup and conditions ....................................................... 88

5.2.2 Hugoniot densities ................................................................................ 89

5.3 Sound velocity measurements......................................................................... 92

5.3.1 Experimental setup and conditions ....................................................... 92

5.3.2 Sound velocity and shock melting ........................................................ 96

5.3.3 Shock temperature and melting curve................................................. 102

5.4 Discussion and geophysical implications ..................................................... 105

5.4.1 Thermal corrections along the geotherm of core ................................ 105

5.4.2 Implications for the composition of the liquid outer core................... 107

References ........................................................................................................... 110

Chapter 6. Summaries and outlook ............................................................................ 115

6.1 Summaries..................................................................................................... 115

6.2 Outlook ......................................................................................................... 117