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Photographs included in the original manuscript have been reproduced xerographically in this copy. 35 mm slides or 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. Accessing the Worldfc Information since 1938 300 North Zeeb Road, Ann Arbor. Ml 48106-1346 USA V Order Number 8804126 Potrogenesis of calc-alkaline and alkaline magmas from the southern and eastern Aegean Sea, Greece Wyers, Gerard Paul, Ph.D. The Ohio State University, 1087 UMI 300 N. Zeeb R4 Ann Arbor, MI 48106 PLEASE NOTE: In all cases this material has been filmed In the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V 1. Glossy photographs or pages _____ 2. Colored Illustrations, paper or print ______ 3. Photographs with dark background ____ 4. Illustrations are poor copy ______ 5. 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Other___________________________________________________________________ University Microfilms International PETROGENESIS OF CALC-ALKALINE AND ALKALINE MAGMAS FROM THE SOUTHERN AND EASTERN AEGEAN SEA, GREECE DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By Gerard Paul Wyers, B.S., M.S. The Ohio State University 1987 Dissertation Committee: Approved by M. Barton K.A. Foland Adviser D.H. Elliot Department of Geology and Mineralogy G. Faure ACKNOWLEDGEMENTS I would like to sincerely thank Mike Barton for his friendship and superb guidance throughout my stay at Ohio State. I am grateful to Ken Foland for his advice on several aspects of my research, and for his help with the acquisition of the isotopic data. Joep Huijsmans (State University of Utrecht) allowed me to use all of his samples, data and calculations, and spent a great deal of time discussing the petrology and geochemistry of Santorini with me. R.D. Schuiling (State University of Utrecht) permitted me to ship the entire sample collection of the Hellenic arc to Ohio State, and Manfred van Bergen let me use the microprobe at Utrecht free of charge. Many thanks also to David Elliot, Gunter Faure and Ken Foland for their constructive comments on my dissertation, and to Chen Jiang Feng and Jeff Linder for their patience while teaching me the required lab skills. Karen Tyler skillfully drafted most of the diagrams in this dissertation and Carolyn Gribbin typed the tables. I am thankful to the Graduate School for awarding me a University Fellowship and a Presidential Fellowship. Additional funding from Friends of ii Orton Hall and the Stichting Molengraaff Fonds is also gratefully acknowledged. Ill VITA September 15, 1960 ....... Born in Utrecht, the Netherlands 1981 ..................... B.S. Cum Laude, Institute for Earth Sciences, Rijksuniversiteit Utrecht 1984 ..................... M.S. Cum laude, institute for Earth Sciences, Rijksuniversiteit Utrecht 1984-present ............. Department of Geology and Mineralogy, The Ohio State University PUBLICATIONS Henderson, C.M.B., Barton, M. and Wyers, G.P.(1984) The transition from alkaline to sub-alkaline lavas in the low-P environment: the role of volatiles. Transactions of the American Geophysical Union 65, 1153. Wyers, G.P. and Barton, M.(1984) Transitional alkaline— sub-alkaline lavas from Patmos, Greece: an example of a magma series formed by fractional crystallization, assimilation and magma mixing. Transactions of the American Geophysical Union 65, 1123. Wyers, G.P. and Barton, M.(1986) Petrology and evolution of transitional alkaline— sub-alkaline lavas from Patmos, Greece. Evidence for fractional crystallization, magma mixing and assimilation. Contributions to Mineralogy and Petrology 93, 297-311. Wyers, G.P. and Barton, M. (1986) Calc-alkaline lavas from Nisyros, eastern Aegean Sea, Greece: evidence for assimilation from trace element studies and Sr-isotope iv results. Transactions of the American Geophysical Union 67, 411. Barton, M., Wyers, G.P., Salters, V.J.M. and Foland, K.A.(1986) Evidence of assimilation during the evolution of two shield volcanoes, Santorini, Aegean Sea, Greece. Transactions of the American Geophysical Union 67, 566. Barton, M. and Wyers, G.P.(1986) The role of subduction in the genesis of primitive alkali basalts from Patmos (Dodecanesos, Greece). Transactions of the American Geophysical Union 67, 1281. Wyers, G.P. and Barton, H.(1986) Geochemistry of a transitional ne-trachybasalt— Q-trachyte lava series from Patmos, Greece: further evidence for fractionation, mixing and assimilation. Contributions to Mineralogy and Petrology 97, 279-291. Gulen, L., Hart, S.R., Salters, V.J.M., Wyers, G.P. and Barton, M. (1987) Sr, Nd, Pb isotopic constraints on the petrogenesis of the Aegean arc volcanics. Terra Cognita 7, 170-171. Wyers, G.P., Barton, M. and Foland, K.A.(1987) Sr- and Nd- isotopic evidence for magma mixing and assimilation in two shield volcanoes on Santorini, Aegean Sea, Greece. Geological Society of America, Abstracts with Programs 19, 900. Wyers, G.P. and Barton, M.(1986) Polybaric evolution of calc-alkaline lavas from Nisyros, southeastern Aegean Sea, Greece. Journal of Petrology, accepted for publication. Barton, M. and Wyers, G.P.(1988) Conditions of crystallization of Tertiary volcanic rocks from Patmos (Dodecanesos, Greece) and implications for magmatic evolution. Journal of Volcanology and Geothermal Research, accepted for publication. FIELDS OF STUDY Igneous Petrology and Isotope Geochemistry v TABLE OF CONTENTS ACKNOWLEDGEMENTS ..................................... ii VITA ................................................. iv LIST OF TABLES ....................................... X LIST OF FIGURES ...................................... xiv CHAPTER PAGE I. INTRODUCTION ................................... 1 Calc-alkaline volcanism .................... 1 The Aegean Sea ............................. 2 Summary of approach ........................ 4 Organization of the dissertation ........... 5 II. POLYBARIC EVOLUTION OF CALC-ALKALINE MAGMAS FROM NISYROS, SOUTHEASTERN HELLENIC ARC, GREECE .... 9 Introduction ................................ 9 Outline of geology......................... 12 Petrography and mineral chemistry .......... 14 Whole-rock major- and trace-element geochemistry ................................ 23 Discussion.................................. 29 Fractional crystallization .............. 29 Major oxide modeling................. 29 Trace element modeling ............... 33 The role of processes other than fractional crystallization .............. 38 Magma mixing ......................... 39 Assimilation.................... 44 Relationships between the basaltic andesite to andesite series and the dacite to rhyodacite series .................... 46 Estimation of the conditions of crystallization ......................... 51 Petrogenetic model ......................... 56 Conclusions ................................. 62 vi III. THE ROLE OF ASSIMILATION - IN THE EVOLUTION OF CALC-ALKALINE MAGMAS FROM SANTORINI AND NISYROS 87 Introduction ............................... 87 Summary of previous w o r k ................... 90 Analytical methods ......................... 92 Results .................................... 93 Mikro Prof it is Ilias .................... 94 Skaros .................................. 95 Nisyros ................................. 96 Discussion................................. 97 Santorini ............................... 99 Intra-cycle variations on Mikro Profitis Ilias ....................... loo Intra-cycle variations on Skaros ..... 104 The role of assimilation on Santorini . 106 Nisyros ................................. ill Relation between mafic magmas from Skaros, MPI and Nisyros ......................... 113 Summary and conclusions .................... 115 IV. THE NATURE OF THE SOURCE REGION OF ISLAND ARC MAGMAS FROM SANTORINI AND NISYROS .............. 142 Introduction .........