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Surface and Crustal Response to Lithospheric Removal Processes: Insights from Numerical and Analogue Modeling

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Surface and Crustal Response to Lithospheric Removal Processes: Insights from Numerical and Analogue Modeling Surface and Crustal Response to Lithospheric Removal Processes: Insights From Numerical and Analogue Modeling by O˘guzHakan G¨o˘g¨u¸s A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Geology University of Toronto Copyright c 2010 by O˘guzHakan G¨o˘g¨u¸s Abstract Surface and Crustal Response to Lithospheric Removal Processes: Insights From Numerical and Analogue Modeling O˘guzHakan G¨o˘g¨u¸s Doctor of Philosophy Department of Geology University of Toronto 2010 Geological, geophysical, and geochemical evidence indicates that a significant portion of the continental mantle lithosphere may be absent in a number of regions near plate boundaries or plate interiors. Delamination and viscous Rayleigh-Taylor instability (\dripping") are widely cited to account for the missing lithosphere, however these removal processes are poorly constrained. This thesis examines the dynamics of delaminating and dripping mantle lithosphere, in particular focusing on the response of the crust to underlying lithospheric removal. Using forward computational models, I explore whether certain (surface) geological observables may be diagnostic of either removal mechanism. Surface topography associated with delamination has a broad zone of uplift above the lithospheric gap and a mobile zone of subsidence at the delamination hinge, whereas with dripping lithosphere, the topographic expression is symmetric and fixed above the mantle lithosphere downwelling. The pattern of surface crustal deformation is also distinctly asymmetric with delamination compared to dripping lithosphere. Expanding on these results, I investigate whether present day geologicalgeophysical observables in Eastern Anatolia are consistent with delamination of the mantle lithosphere. Experimental re- sults demonstrate that well-developed plateau uplift, syn-convergent extension, and crustal thinning in the central part of the Anatolian plateau are consistent with a topographic profile at longitude 42◦E and a geologically interpreted zone of syn-convergent extension in eastern Anatolia. With three-dimensional physical scaled analogue modeling experiments, I consider the process of oceanic plate subduction evolving into continental delamination. Model results show that slower plate convergence with retreating ocean lithosphere subduction can develop into delamination, ii whereas for the experiments with higher plate convergence, the crust above the consumed mantle lithosphere becomes accreted on the retro-plate similar to flake tectonics. The results suggest that delamination is a process analogous to subduction retreat; however, delamination involves decoupling of the retreating mantle lithosphere slab from the buoyant continental crust. iii Acknowledgements I agree after all these years that the doctoral work has been a long and stressful yet, an in- teresting walk/run of both scientific successes and failures. However I have developed many other qualifications along the way; such as, patience, commitment, hard-work, listening(before you an- swer the questions) and defending your work. I owe thanks to many people for helping me to prepare this thesis along the way, people who gave me enough encouragement, support/friendship and motivation to do my best. First and foremost, I'd like to thank my advisor, Russ Pysklywec, for many reasons. Since the day I arrived the department in September 7th of 2004, he made me feel that I knew I have been at the right place. Russ`s encouragement, scientific guidance most importantly his friendship has been immensely helpful. Over the years, I appreciate his special knack for making even the hard problems much easier. The sentence of \Come on O˘guz,you know this" will forever ring in my head. Thank you Russ. I would also like to acknowledge the members of my dissertation committee, who have all helped me immensely throughout my PhD. Jerry Mitrovica and Alexander (Sandy) Cruden have given me insightful recommendations and given me hard moments on my defenses. However it was not long before I realized contributions were to my work overall. I learned a lot from both of them. I would also like to thank Pierre Robin for his additional encouragement and interest in my research. I owe thanks to Claudio Faccenna from RomaTre university who kindly invited me to his lab in Rome to do my analogue modeling studies there and for many fruitful scientific discussions. I am also thankful to Clint Conrad from the University of Hawaii for serving as my external examiner and for his recommendations on my thesis. I would not have come this far if I had not have support/encouragement from my friends at the department. I thank David Boutelier for countless hot-scientific discussions and sharing his graduate school experiences with me. The PhD programme has never been vacation!.Thanks for reminding this David. I thank Sergio Gelcich, Guido Serafini, Chris Charles, Christoph Schrank, Lisa Tutty, Duane Smythe, Abin Das, Guillaume Barlet, for giving me a bit of laughter amidst the many times that I felt like \it was enough". Ed Spooner was the first faculty member I met, when I arrived the department. Our conversations on interesting topics (e.g science, archeology, history, iv soccer etc) has continued until then. Thanks Ed. My friends/colleagues in the department made the last six years of work both fun and memorable for me. Great memories with you guys. Outside of department, I spent most of my ”off time" with friends in Tango, discussing politics- philosophy etc. I have met some of my closest friends in Toronto during the hard and sometimes lonely years of my PhD. I would like to acknowledge Brian Janeway, Hakan Toksoy-Julia Graham, Inan¸c-S¸ima_ Yıldırım, Ilker-Ceren_ So˘gukpınar,Tayfun-Aslı Akku¸s, Defne Berkin, G¨uln¨urOzan, Bedia Tatlısu and Nesime A¸skınwhom thought me that greatest lesson I learned is friendship in whereever you are and independent of how many degrees you have. Last but not least, I thank my family members my father Kemal G¨o˘g¨u¸s, my mom Sevgi G¨o˘g¨u¸s, my sister Inci G¨o˘g¨u¸sAras, my brother in law Ekmel Aras and my nephew Can Deniz Aras for their support, continued love and encouragement. They gave me the support I needed to study on this PhD thesis and to see its ultimate completion from thousands of miles away. I feel very fortunate to have family like you. Well, who would guess that I would meet with such an amazing girl-Corrie 7 months ago at the library and without her companion/support this thesis at the end may not have finished. v \The Sleep of Reason Produces Monsters" Francisco Jos´ede Goya y Lucientes, 1746-1828 vi Contents 1 General Introduction 1 1.1 Introduction . 2 1.2 Physical Conditions for Mantle Lithosphere Removal . 3 1.2.1 The Unstable Mantle Lithosphere Layer . 3 1.2.2 Pre-existing Weak Zone between the Crust and Mantle Lithosphere . 8 1.3 Thesis Structure . 9 1.4 Statement for Authorship . 10 Bibliography 12 2 Near Surface Diagnostics of Dripping or Delaminating Lithosphere 19 2.1 Abstract . 20 2.2 Introduction . 20 2.3 Experimental Results . 25 2.3.1 Model Description . 25 2.3.2 Dripping and Delaminating Mantle Lithosphere . 28 2.3.3 Surface Topography . 31 2.3.4 Moho Temperatures . 34 2.3.5 P-T Histories . 39 2.3.6 Crustal Deformation . 42 2.4 Conclusions and Discussion . 45 Bibliography 49 3 Mantle Lithosphere Delamination Driving Plateau Uplift and Synconvergent Extension in Eastern Anatolia 54 3.1 Abstract . 55 3.2 Introduction . 55 3.3 Modeling Delamination . 58 3.4 Surface Topography and Crustal Deformation . 60 3.5 Delamination Beneath Eastern Anatolia . 63 3.6 Conclusions and Discussion . 65 Bibliography 66 4 The Surface Tectonics of Mantle Lithosphere Delamination Following Ocean Lithosphere Subduction: Insights From Physical Scaled Analogue Experiments 69 4.1 Abstract . 70 vii 4.2 Introduction . 70 4.3 Experimental Design . 75 4.3.1 Model Description . 75 4.4 Experimental Results . 84 4.4.1 Experiment DEL-12 (Vp = 0.25 cm/min) . 84 4.4.2 Experiment DEL-13 (Vp = 0.38 cm/min) . 89 4.4.3 Experiment DEL-11 (Vp = 0.5 cm/min) . 92 4.4.4 Experiment DEL-10 (Vp = 1.0 cm/min) . 95 4.4.5 Delamination and collision: Retreating Plates Beneath the Continental Crust. 98 4.5 Conclusions . 101 4.6 Discussions . 102 4.6.1 Comparison with previous models and natural systems . 102 Bibliography 105 5 Synthesis of Principle Conclusions 112 5.1 Near Surface Diagnostics of Dripping or Delaminating Lithosphere . 113 5.2 Mantle Lithosphere Delamination Driving Plateau Uplift and Synconvergent Exten- sion in Eastern Anatolia . 114 5.3 The Surface Tectonics of Mantle Lithosphere Delamination Following Ocean Litho- sphere Subduction; Insights from Physical Scaled Analogue Experiments . 115 Bibliography 117 Appendix 120 A Description of the Numerical Model 120 viii List of Tables 4.1 Scaling relationships of the reference experiment (DEL-12) . 79 4.2 Experimental parameters of all materials . 80 ix List of Figures 1.1 Mechanical thickening of the lithosphere . 7 2.1 Delamination vs drip model . 24 2.2 Model set-up . 27 2.3 Models' evolution . 30 2.4 Surface topography plots . 33 2.5 Moho temperatures (DEL) . 36 2.6 Moho temperatures (DRIP-1) . 37 2.7 Moho temperatures (DRIP-2) . 38 2.8 P-T history . 41 2.9 Crustal deformation . 44 3.1 Tectonic map of Eastern Anatolia . 57 3.2 Evolution of the model . 59 3.3 Surface topography and crustal thickness . 62 3.4 Comparison of observables (model vs nature) . 64 4.1 Neotectonic evolution of Eastern Anatolia . 74 4.2 Analogue model set-up . 78 4.3 Delamination in analogue modeling . 83 4.4 Model Results Experiment DEL-12 . 88 4.5 Model Results Experiment DEL-13 .
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