Evolution of Rocks from the Münchberg Metamorphic Complex (NE Bavaria)
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Evolution of Rocks from the Münchberg Metamorphic Complex (NE Bavaria) Von der Fakultät Chemie der Universität Stuttgart zur Erlangung der Würde eines Doktors der Naturwissenschaften (Dr. rer. nat.) genehmigte Abhandlung Vorgelegt von Florian Waizenhöfer aus Ellwangen (Jagst) Hauptberichter: Prof. Dr. Hans-Joachim Massonne Mitberichter: Priv.-Doz. Dr. Elmar Buchner Mitprüfer: Prof. Dr. Dietrich Gudat Tag der mündlichen Prüfung: 04. Dezember 2017 Institut für Mineralogie und Kristallchemie der Universität Stuttgart 2017 Inhaltsverzeichnis 1. Abkürzungsverzeichnis ........................................................................................................ 5 2. Zusammenfassungen ............................................................................................................ 7 2.1 Zusammenfassung in deutscher Sprache .......................................................................... 7 2.2 Zusammenfassung in englischer Sprache ......................................................................... 9 3. Prolegomenon ..................................................................................................................... 13 3.1 Motivation ...................................................................................................................... 13 3.2 Geological Frame ........................................................................................................... 14 3.3 Analytical Section ........................................................................................................... 26 3.3.1 Polarisation Microscope ........................................................................................... 26 3.3.2 Electron Microprobe ................................................................................................ 27 3.3.3 Mass Spectrometer ................................................................................................... 29 3.3.4 X-ray Fluorescence Spectrometer and Carbon Analyser ......................................... 31 3.3.5 Verification of Analytical Techniques ..................................................................... 32 4. Monazite in a Variscan Mylonitic Paragneiss from the Münchberg Metamorphic Complex (NE Bavaria) records Cadomian Protolith Ages .............................................. 39 4.1 Introduction .................................................................................................................... 40 4.2 Geological Setting .......................................................................................................... 41 4.3 Analytical Procedures ..................................................................................................... 43 4.4 Mineral Compositions and Textures ............................................................................... 45 4.5 Pressure-Temperature Evolution .................................................................................... 53 4.5.1 Calculation Methods ................................................................................................ 53 4.5.2 Results of the Calculated p-T Pseudosections.......................................................... 56 4.5.3 Construction of the p-T Path .................................................................................... 59 4.6 Age Dating of Monazite ................................................................................................. 60 4.7 Discussion ....................................................................................................................... 63 4.7.1 p-T Evolution, Melting and Mylonitisation ............................................................. 63 4.7.2 Monazite Ages and Their Interpretation .................................................................. 66 4.8 Conclusions .................................................................................................................... 69 5. Contribution to the Metamorphic Evolution of Gneisses from the Münchberg Metamorphic Complex (NE Bavaria) ................................................................................ 71 5.1 Introduction .................................................................................................................... 72 5.2 Geological Setting .......................................................................................................... 72 5.3 Analytical Procedures ..................................................................................................... 75 ii 5.4 Mineral Compositions and Textures ............................................................................... 77 5.5 Results of the Bulk-Rock Analyses ................................................................................ 84 5.6 Pressure-Temperature Evolution .................................................................................... 86 5.6.1 Calculation Methods ................................................................................................ 86 5.6.2 Results of the Calculated p-T Pseudosection of Sample 13Mm6 ............................ 88 5.6.3 Construction of p-T Paths ........................................................................................ 91 5.7 Age Dating of Monazite ................................................................................................. 95 5.8 Discussion ....................................................................................................................... 99 5.8.1 p-T Evolution of the Studied Samples ..................................................................... 99 5.8.2 Monazite Ages and Their Interpretation ................................................................ 101 5.8.3 Protoliths of the Studied Samples .......................................................................... 102 5.9 Conclusions .................................................................................................................. 103 6. Revision of the Pressure - Temperature Evolution of Eclogites from the Münchberg Metamorphic Complex, NE Bavaria (Germany) ............................................................ 105 6.1 Introduction .................................................................................................................. 106 6.2 Geological Setting ........................................................................................................ 107 6.3 Analytical Procedures ................................................................................................... 109 6.4 Mineral Compositions and Textures ............................................................................. 111 6.4.1 Eclogite 13Mm1 ..................................................................................................... 113 6.4.2 Eclogite 13Mm7_2 ................................................................................................. 120 6.4.3 Eclogite MüMa03_3c ............................................................................................. 122 6.5 Results of the Bulk-Rock Analyses .............................................................................. 123 6.6 Pressure-Temperature Evolution .................................................................................. 126 6.6.1 Calculation Methods .............................................................................................. 126 6.6.2 Results of the Calculated p-T Pseudosections........................................................ 128 6.6.3 Construction of p-T Paths on the Basis of the Chemical Zonation of Garnet ........ 131 6.6.4 Hints at p-T Conditions Before and After Garnet Growth ..................................... 136 6.7 Discussion ..................................................................................................................... 138 6.7.1 Protoliths of the Studied Samples .......................................................................... 138 6.7.2 Eclogite-facies Metamorphism of the Studied Samples ........................................ 138 6.7.3 Early Prograde and Late Retrograde p-T Evolution of the Studied Samples......... 140 6.7.4 Geodynamic Consequences ................................................................................... 141 6.8 Conclusions .................................................................................................................. 142 7. Argumentation .................................................................................................................. 143 iii 7.1 Geodynamic Considerations ......................................................................................... 143 7.2 Further Outlook ............................................................................................................ 146 8. Appendix ........................................................................................................................... 149 8.1 Eclogite MüMa12 ......................................................................................................... 149 8.2 Additional Analyses of Eclogite Samples .................................................................... 155 8.3 Additional Analyses of Gneiss Samples ....................................................................... 160 8.4 Analytical Work ........................................................................................................... 163 9. Bibliography ....................................................................................................................