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Analysis and Tectonic Synthesis of the Multiscale Structures Along the Shangdan Tectonic Zone in the Qinling Orogenic Belt, China

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Analysis and Tectonic Synthesis of the Multiscale Structures Along the Shangdan Tectonic Zone in the Qinling Orogenic Belt, China Western University Scholarship@Western Electronic Thesis and Dissertation Repository 5-14-2018 10:00 AM Analysis and Tectonic Synthesis of the Multiscale Structures along the Shangdan Tectonic Zone in the Qinling Orogenic Belt, China Mengmeng Qu The University of Western Ontario Supervisor Jiang, Dazhi The University of Western Ontario Graduate Program in Geology A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Mengmeng Qu 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Tectonics and Structure Commons Recommended Citation Qu, Mengmeng, "Analysis and Tectonic Synthesis of the Multiscale Structures along the Shangdan Tectonic Zone in the Qinling Orogenic Belt, China" (2018). Electronic Thesis and Dissertation Repository. 5383. https://ir.lib.uwo.ca/etd/5383 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Geological structures occur on a vast range of scales in Earth’s lithosphere. Because Earth’s lithosphere is rheologically heterogeneous, a multiscale approach is necessary to relate these structures to the tectonic history of orogens. One such approach, called the multi-order power-law approach (MOPLA), has been developed recently. In this study, MOPLA is applied to the Shangdan tectonic zone (SDTZ) in the Qinling orogenic belt (QOB). The kinematics of the SDTZ and its relation to the country rock deformation are crucial questions for Qinling tectonics, having both been the subject of debate for decades. Detailed work is conducted along the SDTZ to address these two fundamental questions. MOPLA treats a heterogeneous material as a continuum of rheologically distinct elements. The rheological properties of the material and the mechanical fields of the constituent elements are computed by solving the partitioning and homogenization equations self-consistently. The computation is based heavily on the numerical evaluation of Eshelby tensors. This thesis develops an optimal scheme for evaluating Eshelby tensors and implements the scheme in MATLAB to improve the computational efficiency of MOPLA. Multiscale structural analysis is performed along the SDTZ. Three deformation events are identified in the SDTZ and its adjacent areas. D1 deformation is a NE-SW shortening deformation and occurred between ca.385-355Ma. D1 deformation is only observed to the north of the SDTZ in western Qinling. D2 deformation is a strike-slip dominant deformation and occurred between ca.227-201Ma. In western Qinling, D2 i deformation is a dextral strike-slip along the SDTZ. In eastern Qinling, D2 deformation is a sinistral strike-slip along the SDTZ and N-S shortening deformation in the Liuling Group that is south of the SDTZ. D3 deformation is an along-orogen extension and occurred between ca.140-135Ma. D3 deformation is only observed in the Liuling Group in eastern Qinling. D2 deformation, the opposite shearing along the SDTZ and the N-S shortening deformation in the Liuling Group, was a response to the oblique convergence between the South China Block and the North China Block. The convergence angle is constrained to 20°~40° using MOPLA. The tectonic evolution of the QOB from the late Paleozoic to early Mesozoic is illustrated. Keywords Multiscale modeling, Flow partitioning, Structural analysis, Tectonic evolution, Shangdan tectonic zone, Qinling orogenic belt ii Co-Authorship Statement An earlier version of Chapter 2 in this thesis was published as a co-authored paper with my supervisor, Dr. Dazhi Jiang, and Lucy X. Lu (PhD student supervised by Dr. Dazhi Jiang). Qu, M., Jiang, D., Lu, L.X. 2016. An optimal scheme for numerical evaluation of Eshelby tensors and its implementation in a MATLAB package for simulating the motion of viscous ellipsoids in slow flows. Computers & Geosciences 96 (2016): 98- 108. Dr. Jiang thoroughly edited the manuscript and L.X. Lu wrote some part of the MATLAB code in the paper. iii Dedication This work is dedicated to my parents, Qingxia Li and Lin Qu, for their love. iv Acknowledgements While working on the graduate program in Western University, I have benefited greatly from a large group of people. First and foremost, I thank my supervisor, Dr. Dazhi Jiang, for the continuous support of my PhD research, for his immense knowledge on structural geology and tectonics, the never-ending enthusiasm and motivation in different research fields, caring and encouragement during my study at Western and my life in Canada. The accomplishment of this thesis would not be possible without his help. Besides my supervisor, I thank the rest of my thesis committee: Dr. Richard Secco and Dr. Desmond Moser, for their encouragement, insightful suggestions, comments and questions during the comprehensive exam and the committee meeting. I also thank Dr. Desmond Moser for the extra help on the geochronological studies, and I thank Dr. Richard Secco for the suggestions and comments on the preliminary version of this thesis. In addition, I thank Dr. Robert Shcherbakov and Dr. Colin Denniston for the two excellent courses that I have taken. One is ‘Computer Modelling of Natural Processes’ given by Dr. Robert Shcherbakov. During this course, I was surprised by the powerfulness of MATLAB, and thus motivated to move most of my programming work from MathCad to MATLAB. The other course is ‘Scientific Computing’ given by Dr. Colin Denniston in Applied Mathematics department. In this course, I have learned how efficient the computation could be in a parallel computing program. Although I do not have time to apply the parallel computing in my current research, I will definitely apply it into my future work. My sincere thanks also go to my field assistants. In the order of their participation, they are Wenhang Liu, Yuanzhen Yang, Weiyin Chen, Lujun Lin, Teng Wang, Bo Zhang, Rui Yang in summers 2013-2016. I would like to thank Dr. Wei Li and Dr. Wentian Liang in Northwest University for the field guidance in east Qinling and west Qinling, respectively. Without their help, I would not have smoothly and happily conducted the field work during the summer times. v Finally, great thanks give to my family and friends for their love and supports in various aspects. Especially, I thank my colleague Rui Yang for performing the U- Pb dating of samples from the Shetang and Xinyang areas using a laser ablation inductively coupled plasma mass spectrometry at Northwest University. I thank Jiao Zhao for suggestions on processing U-Pb data. I thank Dr. Shuo Sun for the companion during the dark days. I thank my roommate and colleague Lucy Lu for the delicious food, great tea, encouraging words, good discussions and help on writing and debugging. I thank my parents for always trusting me, for giving me all their love and always being there for me. vi Table of Contents Abstract ......................................................................................................................... i Co-Authorship Statement............................................................................................ iii Dedication ................................................................................................................... iv Acknowledgements ...................................................................................................... v List of Tables ............................................................................................................ xiii List of Figures ........................................................................................................... xiv List of Appendices .................................................................................................... xix Nomenclature ............................................................................................................. xx Chapter 1: Introduction ............................................................................................... 1 1.1. The multiscale problem in structural geology studies ..................................... 1 1.2. MOPLA............................................................................................................ 3 1.2.1 The aim of MOPLA ............................................................................. 4 1.2.2 The backbone theory of MOPLA ........................................................ 8 1.2.3 Homogenization systems in MOPLA .................................................. 9 1.3. Application to the Shangdan tectonic zone in the Qinling orogenic belt ...... 11 1.3.1 The problem in the QOB studies .......................................................... 11 vii 1.3.2 The framework of the QOB .................................................................. 15 1.4. Objectives and methodology.......................................................................... 16 1.5. Thesis outline ................................................................................................. 17 1.6. References ...................................................................................................... 18 Chapter 2: An Optimal Scheme for Numerical Evaluation of Eshelby Tensors and Its Implementation in a MATLAB Package for Simulating the Motion of Viscous Ellipsoids in Slow Flows ..........................................................................................
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