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The Central Asia Collision Zone: Numerical Modelling of the Lithospheric Structure and the Present-Day Kinematics

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The Central Asia Collision Zone: Numerical Modelling of the Lithospheric Structure and the Present-Day Kinematics Th e Central Asia collision zone: numerical modelling of the lithospheric structure and the present - day kinematics Lavinia Tunini A questa tesi doctoral està subjecta a l a llicència Reconeixement - NoComercial – SenseObraDerivada 3.0. Espanya de Creative Commons . Esta tesis doctoral está sujeta a la licencia Reconocimiento - NoComercial – SinObraDerivada 3.0. España de Creative Commons . Th is doctoral thesis is license d under the Creative Commons Attribution - NonCommercial - NoDerivs 3.0. Spain License . The Central Asia collision zone: numerical modelling of the lithospheric structure and the present-day kinematics Ph.D. thesis presented at the Faculty of Geology of the University of Barcelona to obtain the Degree of Doctor in Earth Sciences Ph.D. student: Lavinia Tunini 1 Supervisors: Tutor: Dra. Ivone Jiménez-Munt 1 Prof. Dr. Juan José Ledo Fernández 2 Prof. Dr. Manel Fernàndez Ortiga 1 1 Institute of Earth Sciences Jaume Almera 2 Department of Geodynamics and Geophysics of the University of Barcelona This thesis has been prepared at the Institute of Earth Sciences Jaume Almera Consejo Superior de Investigaciones Científicas (CSIC) March 2015 Alla mia famiglia La natura non ha fretta, eppure tutto si realizza. – Lao Tzu Agradecimientos En mano tenéis un trabajo de casi 4 años, 173 páginas que no hubieran podido salir a luz sin el apoyo de quienes me han ayudado durante este camino, permitiendo acabar la Tesis antes que la Tesis acabase conmigo. En primer lugar quiero agradecer mis directores de tesis, Ivone Jiménez-Munt y Manel Fernàndez. Gracias por haberme dado la oportunidad de entrar en el proyecto ATIZA, de aprender de la modelización numérica, de participar a múltiples congresos y presentaciones, y, mientras, compartir unas cervezas. Desde el primer año, desde el máster, con todas esas reuniones semanales, me habéis enseñado a investigar concentrándome en el objetivo, a focalizarme en cada paso para llevar a cabo el proyecto y a no perder el ánimo cuando una revisión duraba más de lo previsto. También me habéis dado muchas recomendaciones para escribir un paper en la mejor manera posible y a darle la importancia adecuada a cada palabra, y aunque sé que ahora mismo estáis deseando que ponga un punto o una coma más, os quiero decir que seguiré intentando escribir frases menos “a la italiana”. Ivone, quiero agradecerte también todas las veces que, con tu calma y sonrisa, has conseguido infundirme ánimos, calmar los nervios y seguir adelante, y por las barbacoas y comidas en tu casa que me han hecho sentirte aún más cercana. Espero que estés contenta de esta experiencia como directora y que te lleves un buen recuerdo de tu primera estudiante de doctorado. Manel, gracias por todo el tiempo dedicado, por los consejos y por evitar que transmitiera mi estrés a los papers, que no es bueno. Gracias también a Juan José Ledo Fernández, por haber aceptado ser el tutor de esta Tesis y haber seguido el trabajo desde el principio, y a Juan Carlos Afonso, por darme la oportunidad de hacer una estancia provechosa en Australia y permitirme utilizar el LitMod, el programa que ha permitido el desarrollo de buena parte de esta Tesis. Big thanks also to Peter Bird, for allowing me to use his SHELLS program and for being there every time we needed an advice. Agradezco también el ICTJA y al CSIC por poner a mi disposición la infraestructura para desarrollar la Tesis y a todo el personal del departamento e del Instituto. En particular, quiero agradecer a Jaume Vergés. Jaume, gracias no solo por todo lo que me has enseñado científicamente sino también porque me has hecho creer en mi trabajo en un momento en el que había perdido la confianza. Un gracias gigante a mis compañeros de despacho, si, a ambos, Alberto y Yan. Gracias por el soporte moral, por aguantar mis altibajos y por todas las conversaciones a puerta cerrada del despacho 300. Ánimo que os falta poco a vosotros también. Gracias a otros compañeros o ex-compañeros del Jaume Almera, con los cuales he compartido momentos de todo tipo dentro y fuera del centro, y con algunos también dentro y fuera de España: Mar, Vinyet, Charlotte, Laura, Giovanni, Sofia, Juan, Stefania, Alexandra, Erika, Emilio, Daniel, Ana, Mireia, Candela, Chusa, Beatriz, Guiomar, Raquel, Helena, Siddique, Massimiliano, Stephanie, Juandi, Israel. Gracias por el Thanks God is Friday, por esa copa, ese café, esa fiesta, esos whatsapp cuando estaba en la tierra de los canguros, ese viaje, la convivencia en ese piso, los findes en el Almera desierto aparte de nosotros. Gracias por esas muchas cosas que han enriquecido los años vividos en Barcelona más allá del doctorado. Un gracias enorme a mis hermanas de Barcelona (aunque, precisamente, de Barcelona no son), que han compartido este viaje conmigo desde el principio: Ileana, Alba y Chiara. Sé que os tendré siempre en mi vida, en cualquier lugar que nos encontremos en el futuro. Ai miei amici sparsi qui e là, con i quali, mi basta una telefonata ed è come se ci fossimo visti ieri. A mis amigos esparcidos por el mundo con los cuales me basta una llamada y es como si nos hubiéramos visto ayer. Francesco, Laura, Elisa, Alicia, Marta, Vanessa, gracias, por los ánimos y por estar siempre ahí. Ai miei amici di sempre, che ogni volta che tornavo a casa mi han fatto sentire come se non fossi mai partita. In ultimo, ma al primo posto per me, un grazie speciale alla mia famiglia, che mi ha sempre dato supporto in ogni decisione, mi ha insegnato a seguire la mia strada e a non mollare mai. A voi, che bene o male avete dovuto ingerire un bel po’ del dietro le quinte del mio lavoro, è dedicata questa Tesi. Funding: The author of this Thesis has benefited from a four-year FPI grant awarded by the Spanish Government between 2010 and 2014. The FPI was supported by the ATIZA project, which was funded by the Ministero de Economía y Competitividad with reference CGL2009-09662- BTE. The author was also granted within the framework of the EEBB (short-term stays) with a 2-month stay at GEMOC ARC National Key Centre, Macquarie University (Sydney, Australia) from 1st June to 31st July 2012. CONTENTS Summary V Part I: Introduction and geological framework 1 Chapter 1: General Introduction 3 1.1 Background and motivation 3 1.2 Objectives 7 Chapter 2: Geological setting 9 2.1 Central Asia 9 2.2 The Arabia-Eurasia collision zone 10 2.3 The India-Eurasia collision zone 14 2.4 The Arabia-India inter-collision zone 17 Part II: Present-day lithospheric structure 21 Introduction 23 Chapter 3: Method: The integrated geophysical-petrological modelling 24 3.1 Mantle temperature distribution 25 3.2 Mantle thermal conductivity 26 3.3 Densities 28 3.4 Potential fields 29 3.5 Mantle seismic velocities 30 3.6 Elevation 30 3.7 Sub-lithospheric anomalies 31 3.8 Mantle characterization 31 Chapter 4: The Zagros orogen 38 4.1 Data 40 4.1.1 Regional geophysical data 40 4.1.2 Crustal structure and depth to the Moho 42 I 4.1.3 Depth to the lithosphere-asthenosphere boundary 44 4.1.4 Mantle seismic velocities 44 4.1.5 Lithospheric mantle composition 46 4.2 Results 48 4.2.1 Crustal structure 49 4.2.2 Lithospheric mantle structure 49 4.2.1 Changing the lithospheric mantle composition 58 4.3 Discussion 60 4.3.1 Geophysical-petrological versus pure-thermal approaches 60 4.3.2 Crustal geometry 61 4.2.1 LAB geometry and compatibility with tomography models 62 4.4 Concluding remarks 63 Chapter 5: The Himalaya-Tibetan orogen 65 5.1 Data 67 5.1.1 Regional geophysical data 67 5.1.2 Previous studies on the crustal and lithospheric mantle structure 69 5.1.3 Upper mantle P-wave tomography 73 5.2 Results and discussion 74 5.2.1 Crustal structure 74 5.2.2 Lithospheric mantle structure 78 5.2.3 Mantle seismic velocities 81 5.2.4 Lithospheric structure variations along the strike of the Himalaya-Tibetan orogen 83 5.3 Concluding remarks 89 Part III: Neotectonic modelling of Central Asia 91 Introduction 93 Chapter 6: Method and model construction 96 6.1 Model domain and faults 97 6.2 Model inputs. Lithosphere and thermal structure 100 II 6.3 Plate motion and boundary conditions 102 6.4 Model constraints 104 Chapter 7: Results 109 7.1 Reference model 109 7.2 Change in the rheological parameters 115 7.3 Change of the lithospheric mantle thickness in NE-Tibet 119 7.4 Changing the velocity conditions in the south-eastern boundary 123 Chapter 8: Discussion and concluding remarks 129 8.1 Discussion 129 8.2 Concluding remarks 133 Part IV: General conclusions 135 Chapter 9: General conclusions 137 List of figures and tables 143 References 151 III IV Summary The Central Asia region is dominated by one of the largest areas of distributed deformation on Earth, which spans eastern Turkey, northern Middle East, central and south- eastern Asia, covering the central and eastern sectors of the Alpine-Himalayan mountain belt. It is composed by the Zagros orogen in the western sector and the Himalaya-Tibetan orogen in the eastern sector, which are the results of the subduction of the Tethys oceanic lithosphere towards the NNE and the subsequent collisions between Arabia and India plates with the Eurasia plate during the Cenozoic. The strong and resistant Archean-to-Proterozoic shields of Arabia and India plates collided with the complex mosaic structure of the Eurasian ancient margin, which was formed by different Gondwana-derived continental blocks accreted by Late-Mesozoic time.
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