Assessing the heterogeneous source of the Azores mantle plume - Beurteilung der heterogenen Quelle des Azoren Mantelplumes Der Naturwissenschaftlichen Fakultät der Friedrich-Alexander-Universität Erlangen- Nürnberg zur Erlangung des Doktorgrades Dr. rer. nat. vorgelegt von Felix S. Genske aus Halle (Saale) Australian Research Council Centre of Excellence for Core to Crust Fluid Systems/GEMOC, Department of Earth and Planetary Sciences, Faculty of Science, Macquarie University Sydney, Australia GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossgarten 5, 91054 Erlangen, Germany Als Dissertation genehmigt von der Naturwissenschaftlichen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg Tag der mündlichen Prüfung: 19.12.2012 Vorsitzender der Promotionskommission: Prof. Dr. Johannes Barth Erstberichterstatter/in: Prof. Dr. Karsten M. Haase Zweitberichterstatter/in: Prof. Dr. Reiner Klemd ii Table of content TABLE OF CONTENT Table of content ........................................................................................... iii! Abstract ......................................................................................................... xi! Abstract (deutsch) ....................................................................................... xii! Statement of Candidate ............................................................................ xiii! Acknowledgements ..................................................................................... xv! Chapter 1: Introduction and Exposition ..................................................... 1! 1.1. Ocean island basalts and mantle plumes .................................................................. 1! 1.2. The Azores islands ................................................................................................... 5! 1.3. The western Azores islands - Flores and Corvo: Chapter two ................................. 9! 1.4. Oxygen isotopes in the Azores: Chapter three ....................................................... 10! 1.5. Lithium and Boron isotopes in the Azores: Chapter four ....................................... 11! 1.6. Constraints on the mantle source from Sr-Nd-Pb-Hf-Os isotopes: Chapter five ... 11! 1.7. The easternmost island - Santa Maria: Chapter six ................................................ 12! 1.8. Thesis framework ................................................................................................... 13! 1.9. Analytical time line ................................................................................................ 14! References ..................................................................................................................... 16! Chapter 2: The Petrology and Geochemistry of Lavas from the Western Azores Islands of Flores and Corvo .......................................................... 27! Abstract .......................................................................................................................... 27! 2.1 Introduction ............................................................................................................. 28! iii Table of content 2.2 Background ............................................................................................................. 29! 2.2.1 Geological Setting ............................................................................................ 29! 2.2.2 Stratigraphy of Flores and Corvo ..................................................................... 32! 2.3 Analytical methods ................................................................................................. 33! 2.3.1 Sampling and sample treatment ....................................................................... 33! 2.3.2 Electron microprobe analysis (EMPA) ............................................................ 34! 2.3.3 Major- and trace-element analysis ................................................................... 34! 2.3.4 Sr and Nd isotopes ........................................................................................... 35! 2.4 Results ..................................................................................................................... 39! 2.4.1 Petrography ...................................................................................................... 39! 2.4.1.1 Primitive lavas and ankaramitic cumulates ........................................................................ 40! 2.4.1.2 Intermediate rocks and trachytes ........................................................................................ 42! 2.4.1.3 The Vila do Corvo flank eruption and hosted cumulates .................................................... 42! 2.4.2 Mineral chemistry ............................................................................................ 45! 2.4.2.1 Olivine ................................................................................................................................. 45! 2.4.2.2 Clinopyroxene ...................................................................................................................... 46! 2.4.2.3 Feldspar ............................................................................................................................... 46! 2.4.2.4 Fe-Ti oxides and spinels ...................................................................................................... 47! 2.4.2.5 Amphibole ............................................................................................................................ 47! 2.4.2.6 Biotite ................................................................................................................................... 48! 2.4.2.7 Accessory phases ................................................................................................................. 48! 2.4.3 Whole-rock geochemistry ................................................................................ 48! 2.4.3.1 Major and trace elements .................................................................................................... 48! iv Table of content 2.4.3.2 Sr-Nd isotope systematics .................................................................................................... 55! 2.5 Quantification of intensive parameters .................................................................... 56! 2.5.1 Geothermobarometry ........................................................................................ 56! 2.5.1.1 Ti-augite geothermobarometry ............................................................................................ 57! 2.5.1.2 Olivine thermometry ............................................................................................................ 60! 2.5.1.3 Amphibole and feldspar thermobarometry .......................................................................... 60! 2.5.2 Oxygen fugacity ............................................................................................... 61! 2.6 Liquid line of descent .............................................................................................. 62! 2.6.1 Primary magma compositions of Flores and Corvo ......................................... 62! 2.6.2 Fractional crystallization .................................................................................. 64! 2.6.2.1 MELTS modeling ................................................................................................................. 65! 2.6.2.2 Trace-element behaviour ..................................................................................................... 68! 2.7 Source composition ................................................................................................. 73! 2.8 Conclusions ............................................................................................................. 75! Acknowledgments ......................................................................................................... 75! Funding .......................................................................................................................... 76! Supplementary data ....................................................................................................... 76! References ..................................................................................................................... 77! Chapter 3: Oxygen isotopes in the Azores islands: the message from olivine ........................................................................................................... 89! Abstract .......................................................................................................................... 89! 3.1 Introduction ............................................................................................................. 90! v Table of content 3.2 Approach and Geological background .................................................................... 91! 3.2.1 Lavas from the Azores islands ......................................................................... 91! 3.2.2 Methods ............................................................................................................ 91! 3.3 Results ..................................................................................................................... 92! 3.3.1 δ18O values of Azores olivines ......................................................................... 92! 3.3.2