Systematics of the post-spinel transition in Fe-bearing compositions [Elektronische Ressource] / von Klaus Schollenbruch

Systematics of the post-spinel transition in Fe-bearing
compositions







Dissertation

zur Erlangung des Doktorgrades

der Naturwissenschaften









vorgelegt beim Fachbereich Geowissenschaften/Geographie

der Goethe Universität Frankfurt

in Frankfurt am Main







von

Klaus Schollenbruch


aus Kaufbeuren






Frankfurt (2010)

(D 30)
20 vom Fachbereich Geowissenschaften/Geographie der Goethe Universität als

Dissertation angenommen











Dekan: Prof. Dr. Robert Pütz











Gutachter: Prof. Dr. Alan Woodland

Prof. Dr. Falko Langenhorst















Datum der Disputation: 17. 12. 2010
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Table of Contents

1. INTRODUCTION ............................................................................................................................................. 5
1.1. OCCURRENCE OF SPINELS ............................................................................................................................. 5
1.2. CRYSTAL STRUCTURE OF SPINELS ................................................................................................................ 6
1.3. USE OF SOME FE-BEARING SPINELS .............................................................................................................. 8
1.4. POST-SPINEL STRUCTURES .......................................................................................................................... 10
1.5. GOAL OF THIS STUDY ................................................................................................................................. 12
1.6. REFERENCES................ 12
2. THE STABILITY OF HERCYNITE AT HIGH PRESSURES AND TEMPERATURES ...................... 20
2.1. INTRODUCTION............. 20
2.2. EXPERIMENTAL METHODS21
2.3. RESULTS AND DISCUSSION ......................................................................................................................... 25
2.3.1. Hercynite breakdown ...................................................................................................................................... 25
2.3.2. A high pressure FeAl O polymorph .............................................................................................................. 30 2 4
2.5. ACKNOWLEDGEMENTS. 31
2.6. REFERENCES................ 31
3. DETECTING THE SPINEL – POST-SPINEL TRANSITION IN FE O BY IN SITU ELECTRICAL 3 4
RESISTIVITY MEASUREMENTS .................................................................................................................. 35
3.1. INTRODUCTION ........................................................................................................................................... 35
3.2. EXPERIMENTAL............ 35
3.3. RESULTS AND DISCUSSION37
3.3.1. The measurements .......................................................................................................................................... 37
3.3.2. TEM investigations ......................................................................................................................................... 39
3.3.3. The phase boundary ................................... 40
3.4. REFERENCES................ 41
4. IN SITU DETERMINATION OF THE SPINEL – POST-SPINEL TRANSITION IN FE O AT HIGH 3 4
TEMPERATURE AND PRESSURE BY SYNCHROTRON X-RAY DIFFRACTION ............................... 44
4.1. INTRODUCTION............. 44
4.2. EXPERIMENTAL METHODS .......................................................................................................................... 45
4.3. RESULTS AND DISCUSSION ......................................................................................................................... 47
4.3.1. In situ observations ......................................................................................................................................... 47
4.3.2. Post-experiment analysis ................................................................................................................................ 51
4.3.3. Additional phases ........................................................................................................................................... 52
4.3.4. The h-Fe O phase .......................................................................................................................................... 52 3 4
4.3.5. TEM observations........................................................................................................................................... 54
4.3.6. The transition .................................................................................................................................................. 55
4.3.7. The phase boundary ........................................................................................................................................ 57
4.4. IMPLICATIONS ............................................................................................................................................ 59
4.5. ACKNOWLEDGEMENTS. 60
4.6. REFERENCES................ 61
5. PHASE TRANSFORMATIONS OF FE O -FE SIO SOLID SOLUTIONS AND FE O -FECR O 3 4 2 4 3 4 2 4
SOLID SOLUTIONS AT HIGH TEMPERATURE AND PRESSURE ........................................................ 65
5.1. INTRODUCTION............. 65
5.2. EXPERIMENTAL............ 66
5.2. RESULTS....................... 68
5.2.1. Fe O – Fe SiO................ 68 3 4 2 4
5.2.1.1. X-ray diffraction ..................................................................................................................................... 68
5.2.1.2. EMPA....................... 70
5.2.2. Fe O – FeCr O............... 71 3 4 2 4
5.2.2.1. X-ray diffraction....... 72
5.2.2.2. EMPA....................... 73
5.2.3. Further characterisation of run-products ......................................................................................................... 74
5.2.3.1. Raman spectroscopy – preliminary measurements ................................................................................. 75
5.2.3.2. Raman measurements on experimental products ................................................................................... 76
5.2.3.3. TEM.......................... 78
5.3. DISCUSSION.................. 78
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5.3.1. Mt-Fay solid solutions .................................................................................................................................... 78
5.3.2. Mt-Chr solid solutions ................................... 80
5.4. FURTHER WORK ......................................................................................................................................... 82
5.5. REFERENCES................ 82
6.A SUMMARY AND OUTLOOK ................................................................................................................... 86
6.1.A HERCYNITE................ 86
6.2.A MAGNETITE............... 87
6.2.1.a Resistivity measurements .............................................................................................................................. 87
6.2.2.a Synchrotron measurements ............................. 88
6.3.A SPINEL SOLID SOLUTIONS ......................................................................................................................... 89
6.4.A REFERENCES.............. 90
6.B ZUSAMMENFASSUNG UND AUSBLICK 93
6.1.B HERCYNIT.................. 93
6.2.B MAGNETIT................................................................................................................................................ 94
6.2.1.b Widerstandsm essungen ................................................................................................................................. 94
6.2.2.b Synchrotron-Experimente ............................................................................................................................. 95
6.3.B MISCHKRISTALLE ..................................................................................................................................... 97
6.4.B REFERENZEN.............. 98
SUPPLEMENTARY MATERIAL .................................................................................................................. 101































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1. Introduction
1. Introduction


1.1. Occurrence of spinels

Spinel-structured minerals (spinels) are common accessory minerals in most kinds of crustal
rocks, where they occur in magmatic, metamorphic and sedimentary rocks. The name of the
whole structural group derives from the mineral spinel (MgAl O ), which originates from the 2 4
Greek word spínos for sparkle.


Fig